Proton sensitive charge-transfer excited states in bis-terdentate cyclometalated Ir(III) complexes: Spectroscopic and theoretical investigation

• Published in: Inorganica Chimica Acta Vol. 471; pp. 8 - 16
• Main Authors: Jacques, Alexandre, Auvray, Thomas, Bevernaegie, Robin, Loiseau, Frédérique, Cibian, Mihaela, Hanan, Garry S., Kirsch-De Mesmaeker, Andrée, Elias, Benjamin
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 24.02.2018; Elsevier Science Ltd; Elsevier
• Subjects: Absorption; Acetic acid; Charge transfer; Chemical Sciences; Chemical synthesis; Emissions; Gas absorption; Iridium; Ligands; MLLCT; Photophysics; Protonation; Spectroscopy; Terdentate; Terdentate; Ir-Py; [Ir-Py-H2]3; Protonation; Iridium; Photophysics; [Ir-Py-H]2; [Ir-Py-Me]2; [Ir-Py-H-Me]3; MLLCT
• ISSN: 0020-1693; 0073-8085; 1873-3255
• DOI: 10.1016/j.ica.2017.10.018

[Display omitted] •Proton sensitive cyclometalated Ir(III) complexes.•Spectroscopic and theoretical investigation.•Metal-Ligand to Ligand Charge Transfer excited states. Two bis-terdentate cyclometalated Ir(III) complexes with polypyridyl (N^N^N) and cyclometalated (C^N^C) ligands [Ir-Py]+ and [Ir-Py-Me]2+ have been synthesized and characterized. Their absorption and emission properties have been examined, more particularly in MeCN as a function of the addition of different acids. Depending on the acid strength and concentration, two distinct effects have been observed. For acetic acid at high concentration or trifluoroacetic acid (TFA) at low concentration, the pyridine moiety of [Ir-Py]+ is protonated; its spectroscopic behaviour is then similar to that of [Ir-Py-Me]2+. Moreover at higher concentration in TFA, the methoxy group of both complexes is protonated. The spectroscopic and electrochemical data as well as the DFT and TD-DFT calculations support contributions of charge-transfer excited states in absorption and emission from metal-ligand/ligand based HOMOs to ligand-based LUMOs, i.e. MLLCT.