0 UNIVERSIDADE ESTADUAL PAULISTA “JÚLIO DE MESQUITA FILHO” Instituto de Química Campus de Araraquara INVESTIGATION OF d, f, AND INTERMETALLIC COMPLEXES AND THE STRATEGIES TO APPLY THEM IN SOLID-STATE LIGHTING DEVICES, OXYGEN SENSING, AND CELL LABELING STUDY Ph. D. Thesis FELIPE DA SILVA MANRIQUE CANISARES ARARAQUARA 2023 FELIPE DA SILVA MANRIQUE CANISARES INVESTIGATION OF d, f, AND INTERMETALLIC COMPLEXES AND THE STRATEGIES TO APPLY THEM IN SOLID-STATE LIGHTING DEVICES, OXYGEN SENSING, AND CELL LABELING STUDY Thesis presented to the Institute of Chemistry, São Paulo State University, to obtain the degree of Doctor in Chemistry Supervisor: Prof. Dr. Sergio Antonio Marques de Lima Co-supervisor: Prof. Dr. Marian Rosaly Davolos ARARAQUARA 2023 FELIPE DA SILVA MANRIQUE CANISARES INVESTIGAÇÃO DE COMPLEXOS d, f, E INTERMETÁLICOS E AS ESTRATÉGIAS PARA APLICÁ-LOS EM DISPOSITIVOS DE ILUMINAÇÃO DE ESTADO SÓLIDO, SENSOREAMENTO DE OXIGÊNIO, E IMAGEAMENTO CELULAR Tese apresentada ao Instituto de Química, Universidade Estadual Paulista, como parte dos requisitos para obter o título de Doutor em Química Orientador: Prof. Dr. Sergio Antonio Marques de Lima Co-orientadora: Profa. Dra. Marian Rosaly Davolos ARARAQUARA 2023 Canisares, Felipe da Silva Manrique C223i Investigation of d, f, and intermetallic complexes and the strategies to apply them in solid-state lighting devices, oxygen sensing, and cell labeling study/ Felipe da Silva Manrique Canisares – Araraquara: [s.n.], 2023 166 p.: il. Thesis (doctor) – Universidade Estadual Paulista, Instituto de Química Advisor: Sergio Antonio Marques de Lima Co-advisor: Marian Rosaly Davolos 1. Rare earth metals. 2. Iridium. 3. Metal complexes. 4. Photoelectronic devices. 5. Aqueous dissolved oxygen. I. Title. Sistema de geração automática de fichas catalográficas da Unesp. Biblioteca do Instituto de Química, Araraquara. Dados fornecidos pelo autor(a). Essa ficha não pode ser modificada UNIVERSIDADE ESTADUAL PAULISTA Câmpus de Araraquara CERTIFICADO DE APROVAÇÃO TÍTULO DA TESE: "Investigation of d, f, and intermetallic complexes and the strategies to apply them in solid-state lighting devices, oxygen sensing, and cell labeling study" AUTOR: FELIPE DA SILVA MANRIQUE CANISARES ORIENTADOR: SERGIO ANTONIO MARQUES DE LIMA COORIENTADORA: MARIAN ROSALY DAVOLOS Aprovado como parte das exigências para obtenção do Título de Doutor em Química, pela Comissão Examinadora: Prof. Dr. SERGIO ANTONIO MARQUES DE LIMA (Participaçao Virtual) Departamento de Física, Química e Biologia / Faculdade de Ciências e Tecnologia - Unesp/ Câmpus de Presidente Prudente Prof. Dr. HERMI FELINTO DE BRITO (Participaçao Virtual) Departamento de Química Fundamental / Universidade de São Paulo - USP - São Paulo Prof. Dr. VERA REGINA LEOPOLDO CONSTANTINO (Participaçao Virtual) Departamento de Química Fundamental / Instituto de Química - USP - São Paulo Prof. Dr. ROBERTO SANTANA DA SILVA (Participaçao Virtual) Departamento de Física e Química / Faculdade de Ciências Farmacêuticas - USP - Ribeirão Preto Prof. Dr. SIDNEY JOSE LIMA RIBEIRO (Participaçao Virtual) Quimica Analitica, Fisico-Quimica e Inorganica / Instituto de Quimica - UNESP - Araraquara Araraquara, 20 de outubro de 2023 Instituto de Química - Câmpus de Araraquara - Rua Prof. Francisco Degni, 55, 14800060, Araraquara - São Paulo http://www.iq.unesp.br/#!/pos-graduacao/quimica-2/CNPJ: 48.031.918/0027-63. PORTARIA UNESP No 117, DE 21 DE DEZEMBRO DE 2022. INSTRUÇÃO AT/PROPG No 02, DE 22 DE DEZEMBRO DE 2022. IMPACTO POTENCIAL DESTA PESQUISA Os potenciais impactos decorrentes desta tese compreendem o aprofundamento do processo de sensibilização em complexos heterobimetálicos de IrIII e EuIII, tanto em ambiente rígido quanto em solução, além de possibilitar o desenvolvimento de dispositivos altamente eficientes no processo de conversão de energia. Tais materiais apresentam potencial para aplicação como dispositivos de iluminação de estado sólido, e sensores luminescentes eficientes na aferição de oxigênio dissolvido, o qual pode servir como poderoso diagnóstico de canceres em estágios iniciais. Desta forma, as contribuições aqui apresentadas potencialmente influenciarão pesquisas voltadas a beneficiar variados setores da sociedade moderna, como as ciências da vida, energia e meio ambiente. POTENTIAL IMPACT OF THIS RESEARCH The potential impacts resulting from this thesis include the understanding of the sensitization process in IrIII-EuIII heterobimetallic complexes, both in a rigid environment and in solution, in addition to enabling the development of highly efficient devices in the energy conversion process. Such materials have the potential for application as solid-state lighting devices and efficient luminescent sensors for measuring dissolved oxygen, which could serve as powerful diagnostic tools for early- stage cancers. Therefore, the contributions presented here can influence research that benefits various sectors of modern society, such as life sciences, energy, and the environment. DATA Personal information Full name: Felipe da Silva Manrique Canisares Name in blibliography Citation: CANISARES, F. S. M.; CANISARES, FELIPE S.M.; CANISARES, F.S.M.; CANISARES, FELIPE S. M. Nationality: Brazilian Birth city: Martinópolis, São Paulo, Brazil Profession: Chemist Adress: Instituto de Química – Universidade Estadual Paulista “Júlio de Mesquita Filho” – Av. Francisco Degni, 55 – Jardim Quintandinha – Araraquara – SP CEP: 14800-060 e-mail: manrique.canisares@unesp.br Academic education 2012 - 2016: São Paulo State University (Unesp), School of Technology and Sciences, Presidente Prudente, Chemistry 2017 - 2019: São Paulo State University (Unesp), Institute of Biosciences, Humanities and Exact Sciences, São José do Rio Preto, Master of Sciences in Chemistry (Advisor: Prof. Sergio A. M. de Lima) 2022 - 2023: Visiting Scholar at University of Southern California, Fulbright Fellow (Advisor: Prof. Mark E. Thompson) Professional Experience 2020 – 2022: Collaborating professor, Biochemistry, São Paulo State University (Unesp), School of Technology and Sciences Awards 2022: Doctoral Dissertation Research Award (DDRA), Fulbright Commission 2016: Honorable Mention at the XXVIII CIC UNESP as one of the best works presented in the Exact Sciences area. 2016: Best Poster Award presented at the XVIII BMIC - Brazilian Meeting on Inorganic Chemistry and 7th Brazilian Meeting on Rare Earths (XVIII BMIC + TR) 2015: Best paper presented in the Inorganic Chemistry Division at 38th Annual Meeting of the Brazilian Chemical Society, SBQ. Published scientific articles 1. MUTTI, ALESSANDRA M. G.; CANISARES, FELIPE S. M. SANTOS, JOÃO A. O.; SANTOS, BRUNO C.; CAVALCANTE, DALITA G. S. M.; JOB, ALDO E.; PIRES, ANA M.; LIMA, SERGIO A. M. Silica-based nanohybrids containing europium complexes covalently grafted: structural, luminescent, and cell labeling investigation JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, v. 106, p. 10971-023-06138, 2023. 2. BELTRAME, ARIANE C. F.; BISPO-JR, AIRTON G.; CANISARES, FELIPE S. M.; FERNANDES, RICARDO V.; LAURETO, EDSON LIMA, SERGIO A. M.; PIRES, ANA M. PMMA or PVDF films blended with β-diketonate tetrakis Eu III or Tb III complexes used as downshifting coatings of near-UV LEDs, v. 19, p. 3992- 4000, 2023. 3. SILVA, RENAN C.; CANISARES, FELIPE S.M.; MUTTI, ALESSANDRA M.G.; PIRES, ANA M.; LIMA, SERGIO A.M. Small Schiff base molecules derived from salicylaldehyde as colorimetric and fluorescent neutral-to-basic pH sensors. DYES AND PIGMENTS, v. 213, p. 111191, 2023. 4. CANISARES, FELIPE S. M.; MUTTI, ALESSANDRA M. G.; SANTANA, EDY F.; OLIVEIRA, VYTOR C.; CAVALCANTE, DALITA G. S. M.; JOB, ALDO E.; PIRES, ANA M.; LIMA, SERGIO A. M. Red-emitting heteroleptic iridium(III) complexes: photophysical and cell labeling study. PHOTOCHEMICAL SCIENCES (ONLINE), v. 21, p. 1077-1090, 2022. 5. CANISARES, FELIPE S.M.; MUTTI, ALESSANDRA M.G.; CAVALCANTE, DALITA G.S.M.; JOB, ALDO E.; PIRES, ANA M.; LIMA, SERGIO A.M. Luminescence and cytotoxic study of red emissive europium(III) complex as a cell dye. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A- CHEMISTRY, v. 422, p. 113552, 2021. 6. MUTTI, A.M.G.; CANISARES, F.S.M.; MACHINI, W.B.S.; PIRES, A.M.; TEIXEIRA, M.F.S.; LIMA, S.A.M. A spectroscopic experimental and semi- empirical study of [Eu(salen)2] as a red-emitter for phosphor-converted UV LED. OPTIK, v. 243, p. 167454, 2021. 7. CANISARES, FELIPE S.M.; BISPO, AIRTON G.; PIRES, ANA M.; LIMA, SERGIO A.M.; Syntheses and characterization of Schiff base ligands and their Ir(III) complexes as coating for phosphor-converted LEDs. OPTIK, v. 219, p. 164995, 2020. 8. LEITE SILVA, CAMILA M.B.; BISPO'JR, AIRTON G.; CANISARES, FELIPE S.M.; CASTILHO, SHIRLEY A.; LIMA, SERGIO A.M.; PIRES, ANA M.; Eu 3+ - tetrakis β-diketonate complexes for solid-state lighting application. LUMINESCENCE, v. 34, p. 877-886, 2019. Submitted scientific articles 1. CANISARES, FELIPE S.M., SILVA, R.C., DAVOLOS, M.R., PIRES, A.M., LIMA. S.A.M., Heterobimetallic IridiumIII-EuropiumIII complex: The role of donor energy on sensitising the EuIII ion. NEW JOURNAL OF CHEMISTRY. 2. SILVA, R.C., CANISARES, FELIPE S.M., SARAIVA, L.F., PIRES, A.M., LIMA. S.A.M., Featuring long-lifetime deep-red emitting iridiumIII complexes with high colour purity: insights on the excited state dynamics from spectroscopic and theoretical perspectives. DALTON TRANSACTIONS. I dedicate this thesis to my parents Oswaldo and Vera Lúcia. Acknowledgments First, I want to thank God for all the wonders He has done and continues to do in my life, for being always with me, whether in good or bad moments. For giving me his infinite Grace, for giving me all his love, for giving me the strength to move forward, no matter the obstacles in the way. I am also grateful for the people He has placed in my life. I thank Our Lady and all the saints for always interceding for me with God. To my parents Vera Lúcia and Oswaldo, my sister Vanessa, and my brother Bruno for always supporting me and believing in me. To all my family, and all the friends I consider part of the family, for always rooting for me. Especially to Ana Maria, Francine, Kaliani, Nataly, and Vanessa, those who believe in and use education as a tool to transform lives. To Professor Sergio Antonio Marques de Lima for his guidance and all his teachings, which were fundamental to the development of this work. To Professor Ana Maria Pires for all her contributions to my work, teaching, and friendship. And for being one of the most human people I have met. I sincerely appreciate all my lab-mates of the LLuMeS, Airton, Alessandra, Alessandro, André, Ariane, Augusto, Bianca, Bruno, Caique, Camila, Danúbia, Edy, Filipe, Gustavo, João, Leonardo, Luis, Maísa, Maria Eduarda, Nagyla, Paloma, Rebeca, Renan, Rodolpho, and Vytor, with whom I shared good moments, experiences, and knowledge. A special thank you to Edy who, throughout my scientific initiation period, had the patience to co-supervise me. To the undergrad students Vytor, and Augusto for their great assistance in the synthesis and purification processes of ligands and complexes. To Renan for his collaborative work related to iridium compounds. To Alessandra for the scientific collaboration in recent years, in which we published beautiful articles. To Ariane for her friendship and scientific collaboration over the last few years, who brought Axé's joy to the lab. To João Antonio for his help with biological assays. To Alessandro for help with photophysical measurements. I am immensely grateful to my “prudentina” family, Shirley, Tamy, and Andressa, for the days of distraction, lots of noise, music, and cooking classes (unfortunately I didn't learn). I mainly thank Andressa, with whom I spent the last years of my doctorate, and we shared such good memories. To my friends from the Chemistry course at FCT-UNESP, with whom I was with every day for 5 years: Thais, Bruno, João, Alessandro, Nathalia, Matheus, Miriam, Aline, and Ricardo. To Professor Aldo Eloiso Job from FCT-UNESP for the use of his laboratories and collaboration in the development of the project. To the Fulbright Commission for the opportunity to develop part of my research in one of the most important research groups on luminescent materials. Especially to Carol, who was always very kind throughout the selection process and the internship period in the United States. To all the Fulbrighters in the 2022–2023 cohort, especially Fernanda, Isis, and Sabrina, the Southern California Fulbrighters, who shared great times with me during this time. To Professor Mark Edward Thompson for opening his laboratory at the University of Southern California (USC) and for the knowledge acquired. To Peter Djurovich for the hours of conversations, which were fundamental in resolving the problems that arose during the development of the project. To Judy Fong, who was very receptive from the first moment I entered the laboratory. To Mattia and Michela, the most Brazilian Italians I know, who made my adaptation process in the United States a little easier. To Mattia and James, with whom I shared hood 3 during my internship. And to all the amazing people I have had the pleasure of meeting and working with: Kelly, Marsel, Allen, Gemma, Jonas, Junru, Collin, Megan, Ao, Konstantin, Nina, Chandler, Francis, Sunil, Eric, Jie, Austin, Mahsa, Caleb, and Sarah. To the teachers who supported me in getting here, from primary education to postgraduate courses. I am extremely grateful to the Institute of Chemistry of the São Paulo State University and to the professors who directly or indirectly influenced my Ph. D studies, especially Professor Marian Rosaly Davolos, for opening the doors of her laboratory and for the support provided during the development of this work. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance code 001. RESUMO A redução do consumo energético por dispositivos de iluminação e imagem, assim como a eficácia na detecção e diagnóstico de doenças por técnicas de imageamento, passa pelo desenvolvimento de materiais emissivos com alta eficiência de emissão. Em ambas as áreas de aplicação, luminóforos vermelhos são de grande interesse, já que por ora podem compor o sistema RGB, possibilitando a geração de qualquer cor luz, inclusive a sensação de luz branca, e ora porque em ensaios biológicos a emissão vermelha distingue-se da autofluorescência do tecido celular, que normalmente ocorre na região do azul ao verde, além da luz vermelha ser menos absorvida pelo sangue, gordura e pele. Complexos emissivos no vermelho com alta pureza da cor são facilmente obtidos através da utilização do íon EuIII, o qual possui bandas estreitas de emissão, todavia, embora os emissores vermelhos baseados no íon EuIII tenham alta pureza de cor, o Φ é tipicamente menor do que emissores baseados em metais do bloco d. Estrategicamente, a síntese de complexos heterobimetálicos d-f, combinando o alto Φ dos complexos do bloco d com a alta pureza de cor dos íons lantanídeos tem sido explorada. Neste contexto, novos sistemas utilizando os íons IrIII e EuIII foram sintetizados e estudados, tendo como foco a compreensão do processo de sensibilização ao íon EuIII em sistemas bimetálicos, assim como estudar as estratégias para aplicá-los em dispositivos de iluminação de estado sólido, no sensoreamento de oxigênio dissolvido, e em imageamento celular. Duas abordagens para sintetizar complexos heterolépticos de IrIII foram estudadas, objetivando obter complexos com diferentes arranjos (cis e trans), ficando evidente que os diferentes arranjos influenciam nas propriedades fotofísicas dos complexos. Dois novos complexos bimetálicos IrIII-LnIII (LnIII = GdIII ou EuIII) foram estudados, e mostraram que o processo de sensibilização ao íon EuIII não é estritamente dependente da diferença energética entre o estado doador e o estado emissor (5D0) quando em solução, já que mesmo que o estado doador 3MLCT esteja situado em região de baixa energia, a sensibilização é um processo favorável quando medido em solventes com alta polaridade. O complexo heterobimetálico de IrIII-EuIII foi imobilizado em filmes de PMMA e aplicado na fabricação de protótipos do tipo LED recoberto, objetivando aplicação em iluminação de estado sólido. Através da modulação da voltagem aplicada ao chip LED UV utilizado como fonte de excitação, determinou-se que a energia mínima do nível doador 3MLCT para observar apenas a emissão vermelha do íon EuIII é de 19.103 cm-1. Por fim, partículas de sílica decoradas com complexos de IrIII-EuIII foram estudadas na detecção de oxigênio dissolvido. As medições na detecção de oxigênio mostraram que o híbrido final tem uma resposta não-linear com sensibilidade de 70,5%. Os testes de toxicidade foram realizados utilizando células Huh-7.5 e as nanopartículas SiO2- EuIIIIrIII foram atóxicas em concentrações entre 1,56 e 400 µg·mL-1. Através de microscopia confocal foi comprovado que as nanopartículas foram internalizadas pelas células mantendo suas propriedades luminescentes, habilitando-as como sondas para imageamento celular. Palavras-chave: lantanídeo; irídio; complexo heterobimetálico; iluminação de estado sólido; sensoreamento de oxigênio. ABSTRACT To reduce the energy consumption of lighting and imaging devices, as well as to increase the effectiveness to detect and to diagnose diseases through imaging techniques, involves the development of emissive materials with high emission efficiency. In both areas of application, red luminophores are of great interest because they can compose the RGB system, enabling the generation of light of any color, including the sensation of white light, and because in biological tests, the red emission is distinguished from the autofluorescence of cellular tissue, which normally occurs in the blue to green region. In addition, red light is less absorbed by blood, fat, and skin. Red emissive complexes with high color purity are easily obtained using the EuIII ion, which have narrow emission bands. However, although red emitters based on the EuIII ion have high color purity, Φ is typically lower than that of emitters based on d- metal complexes. Strategically, the synthesis of heterobimetallic d-f complexes, combining the high Φ of d-metal complexes with the high color purity of lanthanide ions, has been explored. In this context, new systems using IrIII and EuIII ions were synthesized and studied, with a focus on understanding the sensitization process to EuIII ion in bimetallic systems, as well as studying strategies to apply them in solid- state lighting devices, dissolved oxygen, and cell imaging. Two approaches for the synthesis of heteroleptic IrIII complexes were studied, aiming to obtain complexes with different arrangements (cis and trans). It became evident that the different arrangements influence the photophysical properties of the complexes. Two new bimetallic complexes IrIII-LnIII (LnIII = GdIII or EuIII), were studied and showed that the sensitization process to the EuIII ion is not strictly dependent on the energetic difference between the donor state and the emitter state (5D0) when in solution, since when the 3MLCT donor state is in a low-energy region, sensitization is a favorable process if in solvents with high polarity. The IrIII-EuIII heterobimetallic complex was immobilized in PMMA films and used in the manufacture of coated LED prototypes, aiming for application in solid state lighting. By modulating the voltage applied to the UV LED chip used as an excitation source, it was determined that the minimum energy of the 3MLCT donor level to observe only the red emission of the EuIII ion in a rigid system is 19,103 cm-1. Finally, silica particles decorated with IrIII-EuIII complexes were studied for the detection of dissolved oxygen. Oxygen detection measurements showed that the final hybrid has a non-linear response with a sensitivity of 70.5%. Toxicity tests were performed using Huh-7.5 cells, and SiO2-EuIIIIrIII nanoparticles were found to be nontoxic at concentrations between 1.56 and 400 µg·mL-1. Through confocal microscopy, it was proven that the nanoparticles were internalized by cells while maintaining their luminescent properties, making them promising candidates as probes for cellular imaging. Keywords: lanthanides; iridium; heterobimetallic complex; solid state lighting; oxygen sensing List of ligands and polymers Structure Name (Abbreviation) 2-(2,4-difluorphenyl)pyridine (dfppy) 2,2’-bipyridine-3,3’-dicarboxylic acid (bpdc) Pyrimidine-2-carboxylic acid (pmc) 2,4,6-tris(2-pyridyl)-s-triazine (tptz) Tetraethyl orthosilicate (TEOS) 3-(triethoxysilyl)propyl isocyanate (IPTES) 4-(aminomethyl)benzoic acid (abac) Poly(methyl methacrylate) (PMMA) Molecules and particles synthesized in this study Structure Abbreviation [(dfppy)2Ir(µ-Cl)2Ir(dfppy)2] N,N-trans-[Ir(dfppy)2(bpdc)], N,N-(trans)-IrIIIp, or IrIII-p N,N-cis-[Ir(dfppy)2(bpdc)], or N,N-(cis)-IrIIIp N,N-trans-[Ir(dfppy)2(pmc)], or N,N-(trans)-IrIIIm N,N-cis-[Ir(dfppy)2(pmc)], or N,N-(cis)-IrIIIm N,N-trans-[Ir(dfppy)2(tptz)], or N,N-(trans)-IrIIIt N,N-trans-[Ir(dfppy)2(tptz)], or N,N-(cis)-IrIIIt [{Ir(dfppy)2(µ-bpdc)}3Eu2]Cl3·nH2O·mCH3OH IrIII-EuIII [{Ir(dfppy)2(µ-bpdc)}3Gd2]Cl3·nH2O·mCH3OH IrIII-GdIII SiO2 SiO2-NCO SiO2-COOH SiO2-COOEuIII SiO2-COOEuIII-IrIII * For simplicity, only the Δ stereoisomer of the six complexes and IrIII-dimer precursor are represented here, however the classic Nonoyama route lead to a racemic mixture of both Δ and Λ stereoisomers. ** The molecules grafted onto silica particles are out of scale, and merely represent an illustration of the formation of the hybrid. 6 List of figures Figure 1. Emission spectra of selected trivalent lanthanide ions. ........................... 38 Figure 2. Partial energy diagram of EuIII (4f6) showing the relative magnitudes of interelectronic repulsion (terms), spin–orbit coupling (levels), and crystal- field effects (sublevels). On the right side, the emission spectrum of EuIII ion in the [Eu(salen)2] complex is presented. The complex structure is also inserted []. ............................................................................................... 39 Figure 3. Schematic and simplified molecular orbital diagram for an octahedral d6 metal complex involving 2-phenylpyridine (ppy) (C3 symmetry)-type ligands, in which various possible transitions are indicated. On the right side, the emission spectrum of [Ir(ppy)3] complex is presented, and the complex structure is also inserted. Adapted from [50]. ........................... 42 Figure 4. Energy transfer between IrIII complex and EuIII in a bimetallic system. .... 44 Figure 5. The triplet energy of IrIII complexes used to sensitize the EuIII ion in IrIII-EuIII heterobimetallic complexes found in the literature. ................................. 45 Figure 6. a) Representation of the sum of spins used to determine the spin multiplicity; b) representation of spin angular momentum vectors, s1 and s2 iqual ½ to obtain possible values of quantum numbers s’ and m’s. Source: Adapted from []. ...................................................................................... 56 Figure 7. A) The OLED multilayer structure and (B) a scheme of the OLED multilayer energy diagram....................................................................................... 57 Figure 8.Trans and cis isomers of iridium complexes reported in the literature. A) trans and cis N,N-[Ir(2-phenylpyridine)2(2-carboxy-4-dimethyl amino pyridine)] (N984) [116]; B) trans and cis N,N-[Ir(dfppy)2(dfbdpH)Cl] [117]; C) trans and cis N,N-[Ir-(dfptrBz)2(dmbpy)]+ (dmbpy = 4,40-dimethyl-2,20- bipyridine) [118]; and D) trans and cis C,C-[Ir(Ph-Im)2(dmbpy)]+ (Ph-Im = 3-Methyl-1-phenyl-1H-imidazol-3-ium) [119]. ......................................... 59 Figure 9. IrIII-based complexes synthesized in this chapter. ................................... 61 Figure 10. FTIR spectra of the bpdc ligand (black), N,N-trans-IrIIIp (blue), N,N-cis- IrIIIp (red), and the precursor dimer [(dfppy)2Ir(µ-Cl)2Ir(dfppy)2] (green). . 65 Figure 11. FTIR spectra of the pmc ligand (black), N,N-trans-IrIIIm (blue), N,N-cis- IrIIIm (red), and the precursor dimer [(dfppy)2Ir(µ-Cl)2Ir(dfppy)2] (green). 66 Figure 12. FTIR spectra of pmc ligand (green), N,N-trans-IrIIIt (blue), N,N-cis-IrIIIt (red), and the precursor dimer [(dfppy)2Ir(µ-Cl)2Ir(dfppy)2] (black). ......... 67 Figure 13. MALDI spectra of N,N-trans-IrIIIp (black), N,N-cis-IrIIIp (red), N,N-trans- IrIIIm (green), N,N-trans-IrIIIt (purple), and N,N-cis-IrIIIt (wine). ................ 68 Figure 14. Optimized structures of (A) N,N-trans-IrIIIp and (B) N,N-cis-IrIIIp at the r2SCAN-3c/Def2-TZVP level. Grey = carbon, white = hydrogen, green = fluor, blue = nitrogen, and orange = iridium. ........................................... 69 Figure 15. Molecular orbitals of N,N-trans-IrIIIp. (A) HOMO-1, (B) HOMO, (C) LUMO, (D) LUMO+1, (E) LUMO+2. The isosurface was considered with a value of 0.04 e/a0 3. ........................................................................................... 70 Figure 16. Molecular orbitals of N,N-cis-IrIIIp. (A) HOMO-1, (B) HOMO, (C) LUMO, (D) LUMO+1, (E) LUMO+2. The isosurface was considered with a value of 0.04 e/a0 3. ........................................................................................... 70 Figure 17. Optimized structures of (A) N,N-trans-IrIIIm and (B) N,N-cis-IrIIIm at the r2SCAN-3c/Def2-TZVP level. Grey = carbon, white = hydrogen, green = fluor, blue = nitrogen, and orange = iridium. ........................................... 71 Figure 18. Molecular orbitals of N,N-trans-IrIIIm. (A) HOMO-2, (B) HOMO-1, (C) HOMO, (D) LUMO, (E) LUMO+1, (F) LUMO+3. The isosurface was considered with a value of 0.04 e/a0 3. .................................................... 72 Figure 19. Molecular orbitals of N,N-cis-IrIIIm. (A) HOMO-2, (B) HOMO-1, (C) HOMO, (D) LUMO, (E) LUMO+1, (F) LUMO+3. The isosurface was considered with a value of 0.04 e/a0 3. .................................................... 72 Figure 20. Optimized structures of (A) N,N-trans-IrIIIt and (B) N,N-cis-IrIIIt at the r2SCAN-3c/Def2-TZVP level. Grey = carbon, white = hydrogen, green = fluor, blue = nitrogen, and orange = iridium. ........................................... 73 Figure 21. Molecular orbitals of N,N-trans-IrIIIt. (A) HOMO-3, (B) HOMO-2, (C) HOMO, (D) LUMO, (E) LUMO+1, (F) LUMO+2. The isosurface was considered with a value of 0.04 e/a0 3. .................................................... 73 Figure 22. Molecular orbitals of N,N-cis-IrIIIt. (A) HOMO-3, (B) HOMO-2, (C) HOMO, (D) LUMO, (E) LUMO+1, (F) LUMO+2. The isosurface was considered with a value of 0.04 e/a0 3. ....................................................................... 74 Figure 23. Theoretical (dashed) and experimental (continuous) absorption and emission spectra of A) and B) N,N-(trans-cis)-IrIIIp; C) and D) N,N-(trans- cis)-IrIIIm; and E) and F) N,N-(trans-cis)-IrIIIt. .......................................... 75 Figure 24. Excitation and emission spectra of N,N-(trans)-IrIIIp measured in different solvents. ................................................................................................. 77 Figure 25. Excitation and emission spectra of N,N-(cis)-IrIIIp measured in different solvents. ................................................................................................. 77 Figure 26. Excitation and emission spectra of N,N-(trans)-IrIIIm measured in different solvents. ................................................................................................. 79 Figure 27. Excitation and emission spectra of N,N-(cis)-IrIIIm measured in different solvents. ................................................................................................. 80 Figure 28. Excitation and emission spectra of N,N-(trans)-IrIIIt measured in different solvents. ................................................................................................. 81 Figure 29. Excitation and emission spectra of N,N-(cis)-IrIIIt measured in different solvents. ................................................................................................. 81 Figure 30. Timeline representing some of the most important findings of IrIII-LnIII bimetallic systems. ................................................................................. 89 Figure 31. Schematic illustration of potential energy transfer mechanisms in the IrIII- EuIII and IrIII-TbIII complexes. Solid, dashed, and wavy arrows represent excitation, nonradiative processes (energy transfer), and luminescence, respectively. Adapted from [154]. ........................................................... 91 Figure 32. MALDI TOF spectrum obtained to IrIII-EuIII bimetallic complex. ............. 94 Figure 33. A) FTIR spectra of the IrIIIp, IrIII-GdIII, and IrIII-EuIII complexes, B) magnification of the region from 1350 cm-1 to 1650 cm-1. ....................... 94 Figure 34. A) FTIR spectra of the Na2bpdc ligand, IrIII-GdIII, and IrIII-EuIII complexes; and B) most common carboxylate coordination modes and the energy difference between νass(COO−) and νsym(COO−) for each coordination mode in the complexes (Δνc) compared with the energy difference in the ligands (ΔνL). To illustrate, it was used a generic carboxylic acid (benzoic acid). ....................................................................................................... 95 Figure 35. A) emission spectra obtained after each addition of EuCl3; and B) graphic of the ratio of IrIII/EuIII and the energy of the maximum emission of the IrIII complex. ................................................................................................. 96 Figure 36. A) emission spectra obtained after each addition of GdCl3; and B) graphic of the ratio of IrIII/GdIII and the energy of the maximum emission of the IrIII complex. ................................................................................................. 96 Figure 37. Emission spectra acquired in the solid state of IrIIIp, IrIII-GdIII, and IrIII-EuIII complexes. All measurements were carried out with a bandpass of 2.5 nm for both Ex and Em, with an increment of 0.5 nm and an integration time of 0.5 s. The color diagram represents the energy levels of the donor state (3MLCT), and selected states of the EuIII ion. ......................................... 97 Figure 38. Excitation and emission spectra of A) IrIII-p; B) IrIII-GdIII; and C) IrIII-EuIII complexes in the solid state and in various solvents. Concentration in solution of 1.0x10-5 mol·L-1. All measurements were carried out with a bandpass of 2.5 nm for both Ex and Em, with an increment of 0.5 nm and an integration time of 0.5 s. Some IrIII-GdIII emission spectra (chloroform, ethyl acetate, and acetonitrile) are contaminated with EuIII ion, as can be seen by the appearance of a narrow emission band at approximately 616 nm. .................................................................................................. 99 Figure 39. 3MLCT energy state determined using IrIII-GdIII complex measured in different solvents, and emission spectra acquired in chloroform, ethyl acetate, and acetonitrile solution of the IrIII-EuIII complex. Concentration in solution of 1.0x10-5 mol·L-1. All measurements were carried out with a bandpass of 2.5 nm for both Ex and Em, with an increment of 0.5 nm and an integration time of 0.5 s. Full arrows represent favorable energy transfer, and dashed arrows partial energy transfer. ............................ 100 Figure 40. Excitation and emission spectra of IrIII-p, IrIII-GdIII, and IrIII-EuIII complexes measured in A) ethyl acetate, B) acetonitrile, and C) DMSO. Concentration in solution of 1.0x10-5 mol·L-1. All measurements were carried out with a bandpass of 2.5 nm for both Ex and Em, with an increment of 0.5 nm and an integration time of 0.5 s. .................................................................. 102 Figure 41. Excitation and emission spectra of IrIIIp, IrIII-GdIII, and IrIII-EuIII complexes measured in A) methanol and B) water. Concentration in solution of 1.0x10-5 mol·L-1. All measurements were carried out with a bandpass of 2.5 nm for both Ex and Em, with an increment of 0.5 nm and an integration time of 0.5 s. ......................................................................................... 106 Figure 42. Vibrational coupling between the 5D0 emitting level of the EuIII ion and some of the most common quenching oscillators. A generic coordination sphere of EuIII complex is inserted to illustrate the coordination of OH oscillators. ............................................................................................ 108 Figure 43. Excitation and emission spectra of IrIII-p, IrIII-GdIII, and IrIII-EuIII complexes measured in A) dichloromethane, and B) chloroform. Concentration in solution of 1.0x10-5 mol·L-1. All measurements were carried out with a bandpass of 2.5 nm for both Ex and Em, with an increment of 0.5 nm and an integration time of 0.5 s. .................................................................. 110 Figure 44. i) Color-mixed LED based on the combination of three LED chips emitting blue, green, and red light; ii) phosphor-converted LED based on a near- UV-emitting LED chip coated with a mixture of phosphors; 3) hybrid LED based on the blue-emitting LED chip coated with a yellow-emitting phosphor. Hybrid LEDs are often called phosphor-converted LED as well [168]. .................................................................................................... 115 Figure 45. Schematic representation of a p-n junction, showing the electron-hole recombination. ...................................................................................... 116 Figure 46. Timeline of our research group (LLuMeS) in application of SSL. ........ 117 Figure 47. A) Excitation and B) emission spectra of IrIII-p doped films. ................ 119 Figure 48. Excitation, and B) emission spectra of IrIII-p-doped films. C) Photographs of IrIII-EuIII-doped PMMA films acquired using an optical microscopy. .. 120 Figure 49. A) Emission spectra of the UV LED-chip used as the excitation source in blue, of Ir-p:LED prototype in green, and of the Ir-p-Eu:LED prototype in yellow. B) Radiant emission spectra obtained hour after hour for the Ir p- Eu:LED prototype. Inserted the energy diagram illustrating the energy decreasing in the donor state of the Ir-p in the fabricated prototype over time. ...................................................................................................... 122 Figure 50. A) Emission spectra obtained hourly from the Ir-p:LED prototype, and B) Radiant stability of each UV LED prototype analyzed within 18 hours. 123 Figure 51. A) Normalized emission spectra obtained under different voltages from the IrIII-p:LED prototype, and B) Emission spectra obtained by varying the voltage applied to the IrIII-EuIII:LED prototype, from 2.90 V to 3.04 V. .. 123 Figure 52. A) Deconvolution of the emission spectra obtained at 3.00V of the Ir-p- Eu:LED prototype, B) linear fit of the IrIII/EuIII emission area ratio as a function of the energy of the maximum emission band of the Ir-p component in the Ir-p-Eu:LED prototype. ............................................. 124 Figure 53. Schematic representation of the deactivation of triplet states of the phosphorescent molecule by oxygen using the simplified Jablonski diagram. ............................................................................................... 128 Figure 54. Schematic illustration of a ratiometric system (a) use of a dynamic luminophore or (b) two dynamic luminophores. Adapted from [209]..... 130 Figure 55. A) Isolated, B) germinal, and C) vicinal silanol groups on silica particles. ............................................................................................................. 132 Figure 56. Timeline of our research group (LLuMeS) on the development of luminescent materials based on silica particles. ................................... 133 Figure 57. Schematic representation of SiO2-EuIIIIrIII synthetic route, the molecules and the particle are out of scale, and merely represent an illustration of the formation of the hybrid. ......................................................................... 137 Figure 58. A) TEM image of SiO2-EuIIIIrIII particles and B) histogram of the size distribution. ........................................................................................... 138 Figure 59. Vibrational spectra of SiO2 (black), SiO2-NCO (red), SiO2-COOH (green), SiO2-Eu (dark blue), and SiO2-EuIr (light blue). .................................... 139 Figure 60. Experimental and theoretical ratios of C/N in the SiO2-COOH, SiO2-EuIII, and SiO2-EuIIIIrIII samples. *The degree of functionalization was determined using the carbon and nitrogen percentages of the SiO2-COOH sample, since only organic matter was graft ed onto it. In the estimation of the C/N ratio of SiO2-EuIIIIrIII was considered two IrIII complexes coordinated into the EuIII ion, in the illustration here presented, there is only one IrIII represented, for the sake of clarity. .......................................... 140 Figure 61. Thermogravimetric curves of the silica samples. ................................. 141 Figure 62. Surface charge estimated by zeta potential of the SiO2, SiO2-NCO, SiO2- COOH, SiO2-EuIII, and SiO2-EuIIIIrIII samples. ....................................... 142 Figure 63. A) Excitation spectra, B) emission spectra of SiO2-EuIII and SiO2-EuIIIIrIII, and color diagram of SiO2-EuIII and SiO2-EuIIIIrIII samples. ................... 143 Figure 64. Schematic representation of IrIII moiety emission suppression in the SiO2- EuIIIIrIII hybrid. ....................................................................................... 144 Figure 65. Emission spectra obtained at different dissolved oxygen (DO) concentrations, and schematic representation of two main quenching channels to IrIII. ..................................................................................... 145 Figure 66. Variation in the color perception represented by CIE 1931 2° color coordinates. .......................................................................................... 146 Figure 67. Emission lifetime of the IrIII moiety in A) air and B) after purging nitrogen gas. ....................................................................................................... 147 Figure 68. A) Graphical representation of the IrIII/EuIII ratio with dissolved oxygen (DO) variation, and B) Stern-Volmer plot where I0 is the IrIII/EuIII ratio with 0 ppm DO, and I is the IrIII/EuIII ratio with different DO concentrations. 148 Figure 69. Cell viability of SiO2-EuIIIIrIII sample obtained from the Huh 7.5 cell line using MTT assays. ............................................................................... 151 Figure 70. Confocal images of Huh cells incubated with SiO2-EuIIIIrIII sample (50 µg·mL-1). A) Nuclei stained with Hoechst dye; B) IrIII component emission; C) EuIII emission; D) merge of B and C images; E) merge of A and B images; F) merge of A and C images; and G) merge of E and F images. ............................................................................................................. 152 List of tables Table 1. Emission quantum yield of red, green, and blue emitters based on IrIII ion. λem is the maximum emission wavelength, and Φ is the emission quantum yield. ....................................................................................................... 35 Table 2. Comparison of incandescent, fluorescent, LED, and OLED lamps []. ....... 55 Table 3. Root mean square deviation (RMSD) between ground and excited states for each complex. ........................................................................................ 64 Table 4. Molecular orbital composition analysis (%) for each ligand and metal center. Molecular orbital composition analysis (%) for each ligand and metal center. Decomposition was performed through Muliken-partition [] in MultiWFN software []. ............................................................................. 69 Table 5. Molecular orbital composition analysis (%) for each ligand and metal center. Decomposition was performed through Muliken-partition [134] in MultiWFN software [135]. ........................................................................................ 71 Table 6. Molecular orbital composition analysis (%) for each ligand and metal center. The decomposition was performed using the Muliken partition [134] in MultiWFN software [135]. ....................................................................... 73 Table 7. HOMO, LUMO, and energy difference between the HOMO and LUMO orbitals (ΔE = LUMO – HOMO) of the complexes under study. .............. 74 Table 8. Photophysical properties of N,N-(trans)-IrIIIp and N,N-(cis)-IrIIIp complexes measured in different solvents. 𝛷 is the overall emission quantum yield, τ is the emission lifetime, 𝑘𝑟 is the radiative decay rate, and 𝑘𝑛𝑟 is the nonradiative decay rate. ......................................................................... 78 Table 9. Photophysical properties of N,N-(trans)-IrIIIm and N,N-(cis)-IrIIIm complexes measured in different solvents. 𝛷 is the overall emission quantum yield, τ is the emission lifetime, 𝑘𝑟 is the radiative decay rate, and 𝑘𝑛𝑟 is the nonradiative decay rate. ......................................................................... 80 Table 10. Photophysical properties of N,N-(trans)-IrIIIt and N,N-(cis)-IrIIIt complexes measured in different solvents. 𝛷 is the overall emission quantum yield, τ is the emission lifetime, 𝑘𝑟 is the radiative decay rate, and 𝑘𝑛𝑟 is the nonradiative decay rate. ......................................................................... 82 Table 11. Photophysical properties of IrIII-p, IrIII-GdIII, and IrIII-EuIII complexes measured in ethyl acetate, acetonitrile (ACN), and DMSO. 𝛷 is the overall emission quantum yield, 𝜏𝐼𝑟 is the IrIII moiety lifetime, 𝑘𝑟 is the radiative decay rate, 𝑘𝑛𝑟 is the nonradiative decay rate, 𝛷𝐸𝑢𝐸𝑢 is the intrinsic emission quantum yield, 𝜏𝐸𝑢 is the emission lifetime, and Ar and Anr are the radiative and nonradiative decay rates of the 5D0 emissive state of EuIII ion. Concentration in solution of 1.0x10-5 mol·L-1. ................................ 103 Table 12. Judd-Ofelt parameters (Ω2 and Ω4) and area ratio between emission bands related to 5D0→7F2 and 5D0→7F1 transitions. ........................................ 105 Table 13. Photophysical properties of IrIII-p, IrIII-GdIII, and IrIII-EuIII complexes measured in methanol and water. 𝛷 is the overall emission quantum yield, 𝜏𝐼𝑟 is the IrIII moiety lifetime, 𝑘𝑟 is the radiative decay rate, 𝑘𝑛𝑟 is the nonradiative decay rate, 𝛷𝐸𝑢𝐸𝑢 is the intrinsic emission quantum yield, 𝜏𝐸𝑢 is the emission lifetime, and Ar and Anr are the radiative and nonradiative decay rates of the 5D0 emissive state of EuIII ion. ............. 107 Table 14. Judd-Ofelt parameters (Ω2 and Ω4) and area ratio between emission bands related to 5D0→7F2 and 5D0→7F1 transitions. ........................................ 109 Table 15. Photophysical properties of IrIII-p, IrIII-GdIII, and IrIII-EuIII complexes measured in dichloromethane (DCM) and chloroform. 𝛷 is the overall emission quantum yield, 𝜏𝐼𝑟 is the IrIII moiety lifetime, 𝑘𝑟 is the radiative decay rate, 𝑘𝑛𝑟 is the nonradiative decay rate, 𝛷𝐸𝑢𝐸𝑢 is the intrinsic emission quantum yield, 𝜏𝐸𝑢 is the emission lifetime, and Ar and Anr are the radiative and nonradiative decay rates of the 5D0 emissive state of EuIII ion. ........................................................................................................ 111 Table 16. Judd-Ofelt parameters (Ω2 and Ω4) and area ratio between emission bands related to 5D0→7F2 and 5D0→7F1 transitions. ........................................ 111 Table 17. Solvent properties and influence on the photoluminescent properties of IrIII- EuIII bimetallic complex studied in this work. ........................................ 112 Table 18. Percentage values and ratio between carbon and nitrogen calculated (theo.) and found (exp.) for SiO2-COOH, SiO2-EuIII, and SiO2-EuIIIIrIII. . 140 Table 19. Photophysical results from SiO2-EuIII and SiO2-EuIIIIrIII Samples. ......... 143 LIST OF ABBREVIATIONS 1LC singlet ligand-centered transitions 1LLCT singlet ligand-to-ligand charge-transfer 1MLCT singlet metal-to-ligand charge-transfer 3LC triplet ligand-centered transitions 3LLCT triplet ligand-to-ligand charge-transfer 3MLCT triplet metal-to-ligand charge-transfer A acceptor state ATP adenosine triphosphate BC Before Crist BSA bovine serum albumin protein CCT correlated color temperature CFSE Crystal Field Stabilization Energy CPS counts per seconds CRI color rendering index D donor state DCL down-conversion DFT density functional theory DO dissolved oxygen EBL electron blocking layer EML emissive layer ET energy transfer ETL electron transport layer FED forced electric dipole FTIR Furrier transformed infrared HBL hole blocking layer HOMO highest occupied molecular orbital HTL hole transport layer IPTES 3-(triethoxysilyl)propyl isocyanate ISC intersystem crossing ITO indium-tin-oxide LC ligand-centered states LE luminous efficacy LEDs light-emitting diodes LnIII LanthanideIII LOD limit of detection LUMO lowest unoccupied molecular orbital MALDI Matrix Assisted Laser Dersoption/Ionization MC metal-centered states MLCT metal-to-ligand charge transfer states MO molecular orbital MOFs metal organic frameworks MR magnetic resonance MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide NIR near-infrared NMR nuclear magnetic resonance OLEDs organic light-emitting diodes PBS Phosphate buffer saline PET photo-induced electron transfer PLEDs polymeric light-emitting diodes RGB Red, Green, and Blue RMSD Root mean square deviation SMMs Single-molecule magnets SOC Spin-orbit coupling SSL solid-state lighting TD-DFT time-dependent DFT TEA Tetraethylammonium TEOS silicon tetra alkyl orthosilicate TEM transmittance electronic microscopy UCL up-conversion luminescence US United States WLED white light-emitting diode LIST OF SYMBOLS λem maximum emission wavelength τ emission lifetime 𝝉𝑬𝒖 emission lifetime of the europium ion 𝝌 = n(n+2)2/9 correction of the local Lorentz field Φ emission quantum yield 𝜱𝑬𝒖 𝑬𝒖 intrinsic emission quantum yield φ luminous flux δ deformation ΨT total triplet wave function 〈Ѱ𝒇‖Ս(𝝀)‖Ѱ𝒊〉 double reduced elements Ωλ Judd-Ofelt parameters ω angular frequency A01 spontaneous decay rate of the 5D0→7F1 transition Anr nonradiative decay rate of the europium ion Ar radiative decay rate of the europium ion 𝑨𝒕 total decay rate g even (from the German gerade) kn radiative decay rate knr nonradiative decay rate n refraction index Pout optical output power of the source 𝑺𝒇←𝒊 oscillator strength u odd (from German ungerade) νas antisymmetric stretching νs symmetric stretching Table of contents Chapter 1 ................................................................................................................ 35 General introduction, statement of the problem, theory, and review of literature ................................................................................................................................ 35 1.1. Overview .................................................................................................... 35 1.2. Lanthanide Properties ................................................................................ 37 1.3. IridiumIII complexes .................................................................................... 41 1.4. d-f heterobimetallic complexes ................................................................... 43 1.5. General aim of this Ph.D Thesis ................................................................. 46 1.6. Specific aims .............................................................................................. 46 1.7. Characterization techniques ....................................................................... 46 1.8. References ................................................................................................. 48 Chapter 2 ................................................................................................................ 53 IrIII-based complexes: Influence of the synthesis procedure on photoluminescent properties ............................................................................... 53 2.1. Introduction ................................................................................................ 53 2.2. Experimental Procedure ............................................................................. 61 2.3. Structural characterization .......................................................................... 65 2.4. Theoretical calculations .............................................................................. 69 2.5. Photoluminescence study .......................................................................... 76 2.6. Conclusion ................................................................................................. 82 2.7. References ................................................................................................. 83 Chapter 3 ................................................................................................................ 88 IrIII-LnIII Heterobimetallic complexes: The sensitization process of the EuIII ion ................................................................................................................................ 88 3.1. Introduction ................................................................................................ 88 3.2. Experimental Procedure ............................................................................. 92 3.3. Structural characterization .......................................................................... 93 3.4. Photoluminescence study .......................................................................... 97 3.4.1. Non-protic polar solvents ................................................................... 100 3.4.2. Protic polar solvents .......................................................................... 105 3.4.3. Non-polar solvents ............................................................................. 109 3.5. Conclusions .............................................................................................. 112 3.6. References ............................................................................................... 112 Chapter 4 .............................................................................................................. 115 Heterobimetallic IridiumIII-EuropiumIII complex applied in PC-LEDs and the role of donor energy on sensitizing the EuIII ion ...................................................... 115 4.1. Introduction .............................................................................................. 115 4.2. Experimental Procedure ........................................................................... 118 4.3. PMMA film characterization ...................................................................... 119 4.4. PC-LEDs prototypes characterization ...................................................... 121 4.5. Conclusions .............................................................................................. 125 4.6. References ............................................................................................... 125 Chapter 5 .............................................................................................................. 127 Silica particles decorated with IrIII-EuIII heterobimetallic complex for oxygen sensing: a luminescent, cytotoxic, and cell imaging study. ............................ 127 5.1. Introduction .............................................................................................. 127 5.2. Experimental Procedure ........................................................................... 135 5.3. Structural characterization ........................................................................ 138 5.4. Photoluminescence study ........................................................................ 142 5.5. Oxygen sensing ....................................................................................... 144 5.6. Cytotoxic study ......................................................................................... 150 5.7. Cell imaging study .................................................................................... 151 5.8. Conclusions .............................................................................................. 153 5.9. References ............................................................................................... 154 Chapter 6 .............................................................................................................. 159 Final Remarks ...................................................................................................... 159 6.1. General conclusion................................................................................... 159 6.2. Resumo expandido em português ........................................................... 161 35 Chapter 1 General introduction, statement of the problem, theory, and review of literature 1.1. Overview Literature data show a correlation between the emission efficiency and the energy of the maximum emission wavelength from a luminophore [1,2]. Normally, the more red-shifted the emission, the lower the quantum yield, which is explained by the energy gap law [2]. In this way, red emitters normally have lower emission quantum yields than blue or green emitters. Thus, shows the importance of research focusing on the synthesis of new red-emitting compounds to improve the emission quantum yield and to make red emitters comparable with blue and green emitters in terms of efficiency. Some IrIII-based complexes and their respective emission quantum yields in solution are presented in Table 1. Table 1. Emission quantum yield of red, green, and blue emitters based on Ir III ion measured in degassed solution. λem is the maximum emission wavelength, and Φ is the emission quantum yield. Compound λem [nm] Φ [%] Solvent [Ref.] [Ir(mpmi)2(dmpypz)] 466 41.6 DCM [3] [Ir(iprpmi)3] 474 57 DCM [4] mer-[Ir(pmp)3] 465 78 DCM [5] [Ir(Dfpypy)2(fpbpz)] 440,470 87 2-MeTHF [6] [Ir(b5bpm)2(fppz)] 457 85 DCM [7] [Ir(dfppy)2(ptp)] 511,544 39 DCM [8] [Ir(Et-CVz-PhQ)2(pic-N-O)] 595 20 CHCl3 [9] [Ir(EO-CVz-PhQ)2(pic-N-O)] 595 30 CHCl3 [9] red-G1 615 19 Toluene [10] red-G3 622 20 Toluene [10] [Ir(Hlpt)2(bt)] 608,657 3.5 DCM [11] mpmi = 1-(4-tolyl)-3-methyl-imidazolium iodide; dmpypz = 3,5-dimethyl-2-(1 H -pyrazol-5-yl)pyridine; iprpmi = [1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole; pmp = N-phenyl, N-methyl-pyridoimidazol- 2-yl); Dfpypy = 2′,6′-difluoro-2,3′-bipyridine; fpbpz = 3-(trifluoromethyl)-5-(4-t-butylpyridyl) pyrazole; b5bpm = 2-t-butyl-5-(pyridin-2-yl)pyrimidin; fppz = 2-t-butyl-5-(4-t-butylpyridin-2-yl)pyrimidine; dfppy = (3’,5’-difluoro)-2-phenylpyridine; ptp = 2-(5-phenyl-4H-[1,2,4]triazol-3-yl)-pyridine; Et-CVz-PhQ = 9- ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazol; pic-N-O = picolinic acid N-oxide; EO-CVz-PhQ = -(2-(2- methoxyeth-oxy)ethyl)-3-(4-phenylquinolin-2-yl)-9H-carbazole; bt = 2-acetylbenzo[b]thiophene-3- olate; Hlpt=4-methyl-2-(thiophen-2-yl)quinolone. 36 The three colors mentioned above can form a system called RGB (Red, Green, and Blue), in which, through the modulation of the emission of these three fundamental light colors, virtually any light color can be generated. This system is used for all light production that needs color modulation and eventually to create white light, whether for lighting, decorative purposes, or technological applications for screens and displays of electronic devices [12]. Such red emitters are not only important for display applications but also for biological assays as imaging dyes or sensing probes, since the emission of such luminophores can be distinguished from the autofluorescence of the biological medium, which occurs in the blue and green regions [13]. In addition, red light is poorly absorbed by blood, fat, and skin [14]. In this way, as fewer red and infrared photons are absorbed by the body, more photons reach the detector, and more reliable responses can be acquired through imaging. The use of luminescent probes to analyze variables in biological media, such as the concentration of dissolved O2 [15], is very useful in the diagnosis of some diseases because, changes in concentrations can indicate pathological states that can result in cell and/or whole- organism death [16]. Aiming at the two aforementioned applications, lighting and oxygen sensing in biological media, the syntheses and spectroscopic studies of new luminescent IrIII , EuIII, and IrIII-LnIII heterobimetallic complexes grafted or not in silica particles have been carried out for this PhD thesis. The europiumIII ion was chosen because the f-f transitions in lanthanide ions provide a unique light-emitting property [17,18,19]. The 4f orbitals are protected with little influence from the outer chemical environment, which results in narrow emission bands with high color purity. The colors referring to the emission of lanthanide ions vary according to the energetic position of the levels, which in turn depends on the filling of the 4f orbital. The EuIII ion, for example, exhibits a characteristic emission in the red region [19]. However, exploring the luminescent properties of these ions is difficult because they have low molar absorptivity (around 1 – 10 L mol-1 cm-1), typical of f-f transitions, and they are primarily forbidden by Laporte and in some cases by spin selection rule [18]. To overcome the problem of low molar absorptivity imposed on lanthanide ions by the selection rules, an alternative is to coordinate organic molecules [20,21], or d- block metal complexes [22,23,24] into lanthanide ions, which have higher molar 37 absorptivity and are capable of transferring the absorbed energy to the lanthanide ion. This sensitization mechanism is commonly known as the "antenna effect" [25]. This sensitization can be complete or partial, depending on the energy difference between the donor and acceptor levels [26]. In the next topics, we will discuss the fundamental aspects to fully understand the systems under study. 1.2. Lanthanide Properties The lanthanide elements are characterized by the progressive filling of the 4f orbital in its electronic configuration, starting with cerium (Ce, Z=58), and ending with lutetium (Lu, Z=71). Although lanthanum has no electrons in 4f orbital, it is normally classified as lanthanide because of its chemical similarities. When we include scandium (Sc, Z=21) and yttrium (Y, Z=39) elements in this group, which are d block elements but have chemical similarities with the lanthanides, the term rare-earth describes the group. The neutral lanthanides have a common electronic distribution that includes a xenon electronic structure with two or three outer electrons (6s2 or 5d1 6s2) and a, 4fn orbital in between [18]. The electronic configuration of the elements influences their chemical properties, thus molding them to certain applications. Lanthanides are known as internal transition elements because they present in their electronic distributions the 4f sublevel, which is the most energetic level [18]. The colors referring to the emission of lanthanide ions vary according to the energy position of the levels, which in turn depends on the filling of the 4f orbital. For example, the spectra of selected lanthanide ions are presented in Figure 1 [27]. As mentioned before, the low molar absorptivity imposed by Laporte’s selection rule makes it difficult to use trivalent lanthanide ions [27]. The selection rules are derived from the law of conservation of angular momentum, therefore, for a transition to occur, a dipole must be formed [28]. Considering photons as electromagnetic waves with both magnetic and electrical components, a polarized state is required for the molecule to interact with the electric field of the photon, which describes the need to form a dipole. Thus, the greater the strength of the dipole, the greater the probability of the transition. The Laporte´s selection rule states that there will only be an electronic transition when there is a change of parity. When dealing with molecules, parity is related to the molecular orbital (MO) when it undergoes 38 inversion in relation to its center of symmetry [28]. After the inversion, if the wavefunction of the orbital maintains the same sign, it will be even (g, from the German gerade), whereas if the sign changes, it will be odd (u, from German ungerade). In lanthanideIII ions, where transition occurs in the atomic orbitals, the same selection rule describes the forbiddance or allowance because, when the orbital does not present an inversion center, it will be considered even and when there is an inversion center, it will be odd [28]. In this way, all f orbitals are considered odd, which implies that transitions between them are forbidden because there is no parity change. The mechanism that explains such transitions in lanthanide ions is called forced electric dipole (FED) [29]. Figure 1. Emission spectra of selected trivalent lanthanide ions. In 1962, Judd [30] and Ofelt [31] described the importance of the electric dipole mechanism for the intensity of transitions in the 4f orbitals. They considered the mix between fundamental 4fN configurations, where N is the number of electrons in the 4f orbital, with the configurations of excited states of opposite parity caused by the odd term of the Hamiltonian of the ligand field. As mentioned earlier, a transition allowed by an electric dipole only occurs when there is a change in parity between the initial and final states, a condition imposed by the Laporte´s selection rule, which prevents f-f transitions by the electric dipole mechanism. However, when the 200 300 400 500 600 700 800 900 TmIII Wavelength (nm) TbIII EuIII ErIII HoIII 39 lanthanide ion is inserted in a non-centrosymmetric site, it undergoes the influence of the static electric field of the components around the ion, inducing mixing of electronic states of opposite parity with the wave functions of the 4f orbitals, making transitions partially allowed due to the relaxation of the selection rules. This mechanism is called forced electric dipole (FED) [29]. The electrons in a multi-electronic atom suffer perturbations from other electrons, making their states non-degenerate. These perturbations create the spectroscopic terms [26]. The first perturbation is caused by the interelectronic interactions among the electrons in the orbital, resulting in the terms, which is represented by 2S+1L, where 2S+1 is the spin multiplicity and L is the total angular momentum. Then, in heavy atoms, the resultant of spin-orbit coupling, created by the interaction between the magnetic momentum of the electronic spin and the magnetic field, created by the movement of the electron around the nucleus, results in the 2S+1LJ, in which J represents the spin-orbit coupling and varies from S+L to |L-S|, each J level can present a maximum degeneracy of 2J+1. For electrons in an f orbital, these two interactions are much higher than the influence of the crystalline field; however, this interaction, also splits the level into sublevels, which in turn is caused by the interaction between the electrons of the 4f orbital and the electrons of the ligands [26]. Figure 2 shows a schematic energy diagram indicating all three perturbations and their energy variation order for the EuIII ion. Figure 2. Partial energy diagram of EuIII (4f6) showing the relative magnitudes of interelectronic repulsion (terms), spin–orbit coupling (levels), and crystal-field effects (sublevels). On the right side, the emission spectrum of EuIII ion in the [Eu(salen)2] complex is presented. The complex structure is also inserted [32]. 500 550 600 650 700 750 Wavelength (nm) 7 F 4 7 F 3 7 F 0 5 D 0 5 D 0 5 D 0 5 D 0 7 F 1 7 F 2 5 D 0 40 In the Judd-Ofelt theory, the oscillator strength of the electronic transitions comprises three parameters, as shown in equation 1 [33]: 𝑆𝑓←𝑖 = 𝑒2 ∑ Ω𝜆|〈Ѱ𝑓‖Ս(𝜆)‖Ѱ𝑖〉|2 𝜆=2,4,6 (𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 1) where 𝑆𝑓←𝑖 is the oscillator strength of the electronic transition and Ѱ𝑓 and Ѱ𝑖 are the wavefunctions of the initial and final electronic states, respectively. Thus, 〈Ѱ𝑓‖Ս(𝜆)‖Ѱ𝑖〉 represents the double reduced elements to the intermediate coupling, which were determined by Carnall [34] for all lanthanide ions in the 3+ oxidative state in fluoride compounds. In their works, Judd and Ofelt described a model that allows empiric parametrization of the emission intensities of LnIII compounds, which is now known as Judd-Ofelt parameters (Ω𝜆). Herein, it will be discussed in the Judd-Ofelt parameters looking to EuIII ion since this work is based on the energy transfer between IrIII complex and EuIII. The intensities of the 4f-4f transitions are normally expressed in terms of their calculated areas obtained from the emission spectra, from which it is possible to determine the Ω2, Ω4 and Ω6 values using equation 2 [35]: 𝐴0→𝜆 = 4𝜔3𝑒2𝜒 3ћ𝑐3 𝛺𝜆〈 𝐷0 ∣∣ 𝑈(𝜆) ∣∣5 𝐹𝜆〉7 2 (𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 2) where 𝜒 = (𝑛𝑟𝑒𝑓/9)(𝑛𝑟𝑒𝑓 2 + 2)2 is the correction of the local Lorentz field, 𝑛𝑟𝑒𝑓 is the refraction index of the medium, normally 1.5 for most EuIII complexes in the solid state; 〈 𝐷0 ∣∣ 𝑈(𝜆) ∣∣5 𝐹𝜆〉7 2 equals 0.0032, 0.0023, and 0.00023 to λ = 2, 4, and 6, respectively; ω is the angular frequency of the incident radiant field, and 𝐴0→𝜆 is the spontaneous emission rate determined by equation 3 [35,36,37,38]: 𝐴0→𝐽 = 𝐴0→1 ( 𝑠0→𝐽 𝑠0→1 ) (𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 3) A0→1 is the spontaneous decay rate referring to the 5D0→7F1 transition, which is used as an internal standard because it is allowed by the magnetic dipole and is not influenced by the electric field around the system. 𝑆0→1:0→𝐽 are the area of the 5D0→7F1 and 5D0→7FJ transitions (J = 0, 2, 3, 4, 5 and 6), respectively. Normally the 41 Ω6 value is not calculated since the 5D0→7F6 is placed in the near-infrared spectral region and is difficult to detect. In general, all three parameters, Ω2, Ω4 and Ω6 are related to the local symmetry in which EuIII is inserted and also to the polarizability of EuIII ion, although each factor is more pronounced in the determined parameter. The Ω2 is more sensitive to small azimuthal angular variations, on the other hand the Ω4 is more sensitive to the covalent character of the bond between lanthanide ion and the coordinating atoms [35]. 1.3. IridiumIII complexes Recently, many research groups have focused their attention on the development of new iridiumIII compounds because of their versatile applications, such as in biological areas [39,40], catalysis [41], and optical materials [42,43]. In the optical material field, iridiumIII complexes are attractive candidates due to their large spin-orbit coupling (ξ = 4,430 cm-1) [44,45], which harvest most of the excited electrons by mixing singlet and triplet excited states, increasing radiative emission processes and resulting in compounds with high quantum yield values. Furthermore, the emission wavelength can be modulated by changing the ligand structures around the iridium ion [46]. In general, in IrIII complexes, three different types of excited states can occur; (i) metal-centered states (MC), transitions between t2g and eg orbitals; (ii) ligand- centered states (LC), transitions between π and π* orbitals; and (iii) metal-to-ligand charge transfer states (MLCT) [47]. These transitions are presented in the energy diagram in Figure 3. Singlet-singlet absorption (S0→Sn) is an electronic transition between the t2g orbital from IrIII ion (d6, in a quasi-octahedral symmetry and low spin configuration) and the empty ligand orbitals or between ligand orbitals such as π and π*, in this case, there is no spin change, characterizing allowed transitions with large absorption coefficients. On the other hand, singlet-triplet (S→T) transitions present a change in the spin, and as a consequence, they are forbidden, resulting in bands with small extinction coefficients. However, by intersystem crossing (ISC), singlet states may be involved in spin flip, resulting in an excited triplet state with lower energy. The radiative deactivation of the excited states might result in fluorescence when the 42 emissive state has a singlet character or in phosphorescence when it has a triplet character. Figure 3. Schematic and simplified molecular orbital diagram for an octahedral d6 metal complex involving 2-phenylpyridine (ppy) (C3 symmetry)-type ligands, in which various possible transitions are indicated. On the right side, an illustrative emission spectrum of a IrIII-based complex is presented, and the [Ir(ppy)3] complex structure is also inserted. Adapted from [47]. In IrIII complexes, the excited emissive state has a triplet character formed by a mixture of LC and MLCT excited states, resulting in phosphorescence [47]. Because the IrIII ion has a strong spin-orbit coupling constant, the excited singlet states are mostly harvested to triplet states intermediate by ISC, facilitating the production of compounds with high phosphorescence emission quantum yields. However, it is important to point out that not all IrIII complexes will present high emission quantum yields because several deactivation pathways influence the emission property. The IrIII ion as a metallic center in cyclometallated complexes is of special interest for several reasons: (i) it is possible to coordinate specific ligands in a controlled manner due to its quasi-octahedral geometry; (ii) the easy tunability of its photophysical and electrochemical properties; (iii) high molar absorptivity; (iv) the high chemical stability related to oxidation and reduction states, as it has a maximum Crystal Field Stabilization Energy (CFSE ) ‒ or Ligand Field Stabilization Energy (LFSE); and as already mentioned (v) the ability to harvest the singlet states to triplet states resulting in high triplet quantum yields. 400 450 500 550 600 650 700 750 800 Wavelength (nm) 43 1.4. d-f heterobimetallic complexes Monocentered EuIII-complexes had their photophysical and energy transfer process deeply investigated [26], and it was possible to create an energy map between the excited donor state (D) of the ligand and the excited acceptor state (A) of the EuIII ion [48]. These studies report that the energy transfer path occurs in one hand: singlet state (S) → triplet state (T) → EuIII, and in this way, it is considered that the most important parameter is the gap between the ligand triplet state and the excited states of the EuIII ion (5D0 and 5D1) [33]. Normally, better energy transfer in monocentered EuIII-complexes occurs when the triplet D state is energetically close to the excited states of the EuIII ion. Except for Schiff base ligands, where higher quantum efficiency (Φ) is observed when the triplet state (D) has energy closer to the 5D0 emissive state, for other ligand classes it is a consensus that a safe energy distance between D and A states to avoid energy back-transfer is around 2,500 and 3,000 cm-1 [48]. As mentioned, Schiff base ligands sensitize better the 5D0 emitting state [49], while β-diketonate ligands exhibit higher Φ when the D triplet state is above the 5D1 excited state [50], and for polyaminocarboxylates the better acceptor is the 5D2 excited state [51]. Although the red emitters based on the EuIII ion have high color purity, the Φ normally is lower than red emitters based on IrIII complexes. A strategy that has been developed is the synthesis of heterobimetallic d-f complexes or d-f metal organic frameworks (MOFs) to join the high Φ of the d-metal complexes with the high color purity of the lanthanideIII ions. In this field, systems based on IrIII complexes coordinated to the EuIII ion are the most investigated ones [52,53,54]. In a heterobimetallic IrIII-EuIII complex, the IrIII complex acts as a ligand and antenna, and the fundamental idea is that the triplet excited overpopulated state, which is a result of the high spin-orbit coupling of the IrIII ion (ξ = 4,430 cm-1) [55], transfers its energy to the EuIII ion [56]. As well as in monocentered EuIII-complexes, in heterobimetallic IrIII-EuIII complexes, the sensitization efficiency is dependent on the energetic difference between D and A. Data from the literature reveal that the energy transfer efficiency between the D state of IrIII complex and the A state of EuIII ion is not so obvious, because in this case, the D state is also an efficient and long-lived emitter state. Consequently, in such systems, three different situations can occur, as depicted in Figure 4. 44 Figure 4. Energy transfer between IrIII complex and EuIII in a bimetallic system. (i) When the D state is energetically lower than the emissive state of EuIII ion, sensitization does not occur, as expected, and the IrIII complex is not a good antenna for the EuIII ion. This is the case of [{(ppy)2Ir(μ-pmc)}3EuCl3] heterobimetallic complex reported by Lian et al. [57], in which the D state is at approximately 16,666 cm-1, and it is situated below the 5D0 emitting level of the EuIII ion (17,225 cm-1) [58], accordingly only the emission from the IrIII-complex component is detected. By increasing the D energy state to be energetically higher than 5D0, the sensitization efficiency increases until it reaches its maximum. (ii) If the D-state is higher but close to the A-state, the energy might be transferred partially, characterizing an emission spectrum with both emissive components, a broad band from IrIII component, and narrow emission bands from EuIII. (iii) If the D-state is higher than the A-state to avoid energy back-transfer, the emission spectrum will show only the narrow emission bands from EuIII. A few heterobimetallic complexes with efficient energy transfer to the EuIII ion have been reported, such as [{(dfppy)2Ir(µ-phen5f)}3EuCl]Cl2 published by Chen et al. [24], where the D state is centered at 20,408 cm-1; Jiang et al. [54] also reported a heterobimetallic complex with efficient energy transfer, i.e., the [{Ir(dfppy)2(cbphen)}3ClEu]Cl2, in which the D state is situated at 19,230 cm–1 at room temperature in dichloromethane solution. In both cases, solely emission from the EuIII component is observed. 450 500 550 600 650 700 Wavelength (nm) 450 500 550 600 650 700 750 800 Wavelength (nm) 450 500 550 600 650 700 750 800 Wavelength (nm) 45 If the D-state energy is much higher than the 5D0 energy, a fourth situation will be observed, and there will be emission from both components due to the poor energy transfer efficiency, and a spectrum-like situation (ii) is expected, which has been reported for several IrIII-EuIII bimetallic systems [23,57,59]. In these studies, values of D states above 21,690 cm-1 make the energy transfer process inefficient. Systems based on multiple emissive states find several applications, such as lighting to create white light [60], or in luminescent ratiometric probes for analyzes in environmental [61] and biomedical fields [62]. Some IrIII complexes used as ligands in IrIII-EuIII heterobimetallic complexes are presented in Figure 5, to each complex it is showed the energy of the triplet excited state, the donor state. The light blue region represents the energy gap in which the energy transfer between IrIII complex and EuIII ion is favorable; thus, only red emission from the EuIII ion is observed. Figure 5. The triplet energy of IrIII complexes used to sensitize the EuIII ion in IrIII-EuIII heterobimetallic complexes found in the literature. 0 2 16 18 20 22 24 (ii) Partial energy transfer (iii) Favorable energy transfer (ii) Partial energy transfer En e rg y / cm -1 5D0 - (17225 cm-1) (i) No favorable energy transfer 46 1.5. General aim of this Ph.D Thesis Development and spectroscopy study of luminescent complexes and decorated silica particles aiming for solid-sate lighting application (SSL), oxygen sensing, and cellular imaging. 1.6. Specific aims Chapter 2: Synthesis and characterization of cis and trans heteroleptic IrIII-based complexes, and analysis of the influence of the different arrangements in the photophysical properties. Chapter 3: Synthesis and characterization of heterobimetallic complexes based on IrIII-LnIII (LnIII = EuIII or GdIII), and analysis of the influence of the solvent on the sensitization process of the EuIII ion. Chapter 4: Immobilization of the heterobimetallic IrIII-EuIII complex in PMMA films, and application as phosphor-converted UV LED (PC-LED). Chapter 5: Synthesis and characterization of silica particles decorated with heterobimetallic IrIII-EuIII complex aiming for oxygen sensing and cell imaging study. 1.7. Characterization techniques Absorption spectroscopy: Measurements were collected using a Shimadzu model UV-1800 spectrometer, double beam, within the 900 - 200 nm spectral range and resolution of 1 nm. MALDI TOF analysis: Spectra were collected in a Bruker Daltonics auto flex III smart beam by using malono matrix placed in Federal University of Minas Gerais (UFMG) in Belo Horizonte - MG. FTIR analysis: Infrared spectra were recorded using an FTIR IRAffinity-1 Shimadzu spectrometer within the 4,000 – 400 cm-1 range, recorded using 100 scans, resolution 47 of 1 cm-1, in ATR mode. This instrument is placed at University of São Paulo State (UNESP) in Presidente Prudente Campus. Transmission Electron Microscopy (TEM): Images were collected from a JEM2100 LaB6 (TEM) equipped with chemical analyses (energy dispersive spectroscopy - EDS). The equipment is placed at Chemistry institute of São Carlos (IQSC). Confocal Microscopy: The images were collected from a Carl Zeiss LSM 800 com Airyscan. The Confocal LSM 800 has three detection channels, the third being a super resolution "Airyscan" model with GaAsp detector, system with four laser lines, 405 nm, 488 nm, 561 nm and 640 nm and transmitted light detector, objectives in 10x, 20x, 40x oil immersion fluoride crystal and 40x LD, 63x/1.4 oil immersion planapochromatic objective for super resolution. Elemental Analysis (CHN): Data from chapter 3 were collected in a Perkin Elmer 2400 series ii, which can determine carbon, nitrogen, hydrogen, and sulfur (CNHS). The equipment is located at Institute of chemistry at University of São Paulo. Luminescent measurements: The data from chapter 2, 3, and 5 were collected at Institute of Chemistry of University of São Paulo State (IQ UNESP) in Araraquara - SP, using a Horiba Jobin Yvon Fluorolog-3 Spectrofluorometer, model Fluorolog-3 - 221, using a continuous 450 W-Xenon lamp, double excitation and emission monochromator, and an R 928 Hamamatsu photomultiplier. The absolute emission quantum yield values were recorded using an integrating sphere with an absolute error of 10% in its value. Data from chapter 4 were acquired in University of São Paulo State (UNESP) campus of Presidente Prudente - SP, using a Perkin Elmer model LS55 spectrometer. Thermal analysis – Thermogravimetry: Thermogravimetric measurements were performed using TA Instruments model SDTQ600 equipment, which operates simultaneous DSC and TGA measurements. This equipment is in the X-ray Diffraction Laboratory under the coordination of Prof. Silvio Rainho Teixeira from the Department of Physics at FCT – UNESP – Presidente Prudente. 48 Scanning Electron Microscopy (SEM): Scanning electron microscopy measurements were carried out on a Carls Zeiss microscope, model EVO LS15, using a secondary electron detector (SE) in high vacuum and constant temperature. The sample was metallized with a thin layer of gold using the Sputerring Quorum model Q 150 R ES. 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[62] ZHUANG, Yuan et al. Ratiometric fluorescent bioprobe for highly reproducible detection of telomerase in bloody urines of bladder cancer patients. Acs Sensors, v. 1, n. 5, p. 572-578, 2016. 53 Chapter 2 IrIII-based complexes: Influence of the synthesis procedure on photoluminescent properties 2.1. Introduction There is currently great concern about energy consumption, especially non- sustainable and non-renewable sources that is directly associated with environmental problems [63]. Recent surveys in developed countries show that approximately 20% of all energy production is used for operating and maintaining imaging devices and light production [63,64,65]. This large energy consumption by emissive devices shows the need to develop materials with better performance in the energy conversion process (quantum yield), also seeking cheaper production and fewer environmental impacts. The advent of artificial lighting dates back 500,000 years, when the Neanderthals manipulated fire [66]. In this first moment of combustible light sources, dry tree branches were burned to produce light, thus making it possible to extend daily activities into the night. Much later, between 30,000 and 70,000 years ago, the first wick was dated using a capillary immersed in a fuel composed of melted fat [67]. Oil-based fuels to maintain light generation were the main source until about 5,000 BC, for this purpose, oils extracted from fish, castor, nuts, sesame, and so on were used [67]. In 3,000 BC, in ancient civilizations such as the Babylonian and Egyptian, light was considered a luxury artifact enjoyed only by the richest part of society, in which simple oil lamps were used [68]. More sophisticated oil lamps were introduced in 1784 by the Swiss Aimé Argand (1750-1803), which today is called the Argand oil lamp [69]. In its construction, Argand used a tubular wick surrounded by a glass smokestack, this invention obtained English patent nº 1425 [70]. Previously, in 1772, in Scotland, William Murdoch (1754-1839) created gas-burning lighting. This invention was used for a long time to mainly illuminate public roads [71]. In 1879, Thomas Edison (1847-1931), an American researcher and entrepreneur, and the British chemist, electrical engineer, and inventor Joseph Swan (1828-1941) invented the incandescent filament lamp [72]. Although inefficient, this was the first time that 54 light was generated without combustion, odor, or smoke and dominated the market until recent years [67]. From these first lamps, it was possible to create some parameters to quantify and qualify the aspects of the light generated for lighting purposes. The first parameter is the luminous efficacy (LE), which is defined as the ratio between the luminous flux (φ) and the optical output power of the source (Pout), as shown in the simplified equation 4. In other words, LE measures how much light is generated by a unit of power; thus, LE is given in lm·W-1 [73]. 𝐿𝐸 = φ 𝑃𝑜𝑢𝑡 (𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 4) Considering this first aspect, incandescent lamps are very inefficient, as most of the energy supplied (95%) is dissipated in the form of heat [74], since the generation of light in these lamps is ascribed to the incandescence of a filament, currently composed of tungsten (W), but in Edison's version carbonized paper and later Japanese bamboo fiber were used [67]. Another important parameter used to qualify the quality of the generated light is the color rendering index (CRI) [75]. This parameter measures the ability of an artificial light source to faithfully reproduce the colors of objects compared with a r