Near-UV to red-emitting charged bis-cyclometallated iridium(III) complexes for light-emitting electrochemical cells

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 41; no. 1; pp. 180 - 191
• Main Authors: Kessler, Florian, Costa, Rubén D, Di Censo, Davide, Scopelliti, Rosario, Ortí, Enrique, Bolink, Henk J, Meier, Sebastian, Sarfert, Wiebke, Grätzel, Michael, Nazeeruddin, Md Khaja, Baranoff, Etienne
• Format: Journal Article
• Language: English
• Published: England 07.01.2012
• Subjects: Accessibility; Charging; Electrochemical cells; Electroluminescence; Emission; Excitation; Ligands; Mathematical analysis
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c1dt10698h

Herein we report a series of charged iridium complexes emitting from near-UV to red using carbene-based N^C: ancillary ligands. Synthesis, photophysical and electrochemical properties of this series are described in detail together with X-ray crystal structures. Density Functional Theory calculations show that the emission originates from the cyclometallated main ligand, in contrast to commonly designed charged complexes using bidentate N^N ancillary ligands, where the emission originates from the ancillary N^N ligand. The radiative process of this series of compounds is characterized by relatively low photoluminescence quantum yields in solution that is ascribed to non-radiative deactivation of the excited state by thermally accessible metal-centered states. Despite the poor photophysical properties of this series of complexes in solution, electroluminescent emission from the bluish-green to orange region of the visible spectrum is obtained when they are used as active compounds in light-emitting electrochemical cells.