Synthesis and Photophysical Properties of (Cl2Ph)Salen‐based Indium Complexes

Abstract

Herein, to elucidate the effect of substituent electronic properties on the photophysical properties of indium‐based organometallic luminophores, we prepare a series of indium complexes (1–5) with salen ligands bridged by an electron‐withdrawing 4,5‐dichlorophenylene (Cl2Ph) unit. The structures of all the complexes are fully confirmed by 1H and 13C NMR spectroscopy as well as elemental analysis. In particular, the molecular structure of 3, confirmed by X‐ray crystallography, is monomeric and the central indium atom adopts a square‐pyramidal geometry. The UV/Vis and fluorescence spectra of 1–5 show typically salen‐centered intramolecular charge transfer transitions with gradual bathochromic shifts as the electron‐donating ability of the substituents increases. This feature is further supported by electrochimical studies. Furthermore, the lowest unoccupied molecular orbital energy levels of 1–5 are considerably lower (approximately −3.70 eV) than those of salen‐based indium complexes with other aryl‐bridging units owing to the reduced electron‐donating effect of the (Cl2Ph)salen group.