Synthesis and Characterization of Heteroleptic Bis-Cyclometalated Iridium(III) Complexes

Abstract

• Heteroleptic bis-cyclometalated Ir(III)-NHC complexes were synthesized. • The reaction system is simple and easy to be handled. • The iridium(III) complexes exhibited photoluminescence and fluorescence lifetimes. Several heteroleptic bis-cyclometalated iridium(III) complexes containing ancillary N-heterocyclic carbene ligands were synthesized in medium to good yields under mild reaction environment. The desired Ir(III) complexes have been characterized by nuclear magnetic resonance spectroscopy, electronic absorption, emission spectroscopy, cyclic voltammetry and fourier transform infrared spectrum (FT-IR). Each of the [(C ˄ N) 2 Ir(NHC)] complexes exhibited strong photoluminescence with quantum yields ( ϕ PL ) ranging from 1.35% to 41.41% and fluorescence lifetimes around 43 ns in dichloromethane solution at room temperature. These results showed that the electrochemical and photophysical properties of heteroleptic bis-cyclometalated iridium(III) complexes were analogous, furthering the conclusion that the electronic structure and excited-state dynamics were not influenced by auxiliary ligands modification.