Charge transfer properties of diarylamine-substituted phenyl osmium(II) compounds

Abstract

The localization or delocalization of charges and charge transfer characteristics in organometallic complexes, have consistently been significant areas of research. In this study, we investigate the charge distribution and transfer properties of four organometallic complexes containing Os(II) and triarylamine (NAr₃) ligands. These compounds display dual single-electron oxidation waves: the initial oxidation involves the NAr₂ unit and π(C₆H₃) segment, followed by a subsequent process primarily centered on Os(II) and π(C₆H₃). The oxidation potential and reversibility of these compounds within this series are contingent upon the positioning of the NAr₂ acceptor and the Os(II) donor on the benzene ring, along with their mutual interactions. Through ultraviolet-visible-near-infrared (UV–Vis-NIR) absorption spectroscopy, observable charge transfer metal-to-ligand charge transfer (MLCT) absorptions from ClOs to NAr₂⁺ and distinct absorption features of NAr₂^‧+ are identified. Notably, ligand-to-ligand charge transfer (LLCT) band emerges in the para isomer (Cl→NAr₂⁺) and in the metamer (π(PMe₃–ClOs−C₆H₃)→ NAr₂⁺). Furthermore, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are in agreement with the results obtained from electrochemical experiments, electronic properties, and optical behavior.