Synthesis, Structures, Optical, and Electrochemical Properties of Bis-Cyclometallated Iridium(III) Complexes with N-Benzylbenzimidazoles

A series of bis-cyclometallated iridium(III) complexes with various 2-aryl-1-benzylbenzimidaz-oles (aryl is 4-chlorophenyl, 4-tert-butylphenyl, 3,4-dimethoxyphenyl) and 4,4'-dicarboxy-2,2'-bipyridinehave been prepared. The synthesized complexes have been studied by 1H NMR spectroscopy, high-resolution mass spectrometry, X-ray diffraction analysis, spectrophotometry, luminescent spectroscopy, and cyclic voltammetry. In the electronic spectra of the complexes, the absorption bands show a noticeable bathochromicshift with an increase in the electron-donating properties of the benzimidazole ligand. In solution, the complexesexhibit photoluminescence in the yellow-red region of the spectrum with a quantum yield in the range of 0.4-7.7% and an excited state lifetime in the range of 71-408 ns. According to cyclic voltammetry data, quasi-reversibleredox transitions are observed in solutions of the studied complexes (E-ox = 1.16-1.57 V vs. SHE, acetonitrile).