Cyclometalated Ruthenium, Osmium, and Iridium Complexes Bridged by an NCN-Pyrene-NCN Derivative - Synthesis and Comparison of Optical, Thermal, and Electrochemical Properties

New ruthenium (Ru), osmium (Os), and iridium (Ir) complexes bridged by the cyclometalating ligand 1,3,6,8-tetra[4-(2,2-dimethylpropyloxy)-2-pyridyl] pyrene and containing terminal 4'-(4-metoxynaphthalene-1-yl)-2,2': 6', 2 ''-terpyridine ligands were synthesized, and the effects of the metal center on their diverse properties were evaluated. Thermal measurements showed that the obtained complexes retain high thermal stabilities. The structural properties were evaluated through density functional theory (DFT) calculations. Furthermore, spectroscopic and theoretical studies through timedependent DFT (TD-DFT) calculations revealed the characters of the transitions; metal-to-ligand charge-transfer (MLCT) excitations are predominant for Ru and Os and weakly observed for Ir. Electrochemical studies revealed considerable differences between the complexes.