Synthesis, Structure, and Optical and Electrochemical Properties of a Chromophoric Cyclometalated Iridium(III) Complex

Abstract

A new N-donor ligand, methyl 4-(1-methyl-1H-pyrimidin-2-yl)nicotinate, and an octahedral cationic iridium(III) complex based on it (I) have been synthesized. 1-Benzyl-2-phenyl[2,3]naphthimidazole was used as the cyclometalated ligand, and \({\text{PF}}_{6}^{ - }\) serves as the counterion. Compound I was characterized by ¹H, ¹³C, ¹⁹F, ³¹P, ¹H,¹H–COSY, and ¹H,¹H–NOESY NMR spectroscopy, high-resolution mass spectrometry, and X-ray diffraction analysis. Due to the coordination of ligands with extended conjugated systems around the metal ion, the target complex absorbs light up to 700 nm (ε ~ 1000 M^–1 cm^–1), which accounts for its intense coloration. Complex I exhibits reversible electrochemical behavior in the positive potential range with E_1/2 = 0.58 V vs. \({{E}_{{{{{\text{F}}{{{\text{c}}}^{ + }}} \mathord{\left/ {\vphantom {{{\text{F}}{{{\text{c}}}^{ + }}} {{\text{Fc}}}}} \right. \kern-0em} {{\text{Fc}}}}}}}\). Based on its key characteristics, the obtained compound surpasses most iridium analogs and appears promising for further evaluation in photovoltaic devices.