Fine‐Tuning of Photophysical and Electronic Properties of Materials for Photonic Devices Through Remote Functionalization

Abstract

Abstract We report four new iridium(III) complexes of the type [Ir(ppy) 2 (N∧N)][PF 6 ] in which N∧N is a 4,6‐diphenyl‐2,2′‐bipyridine and the 4‐phenyl ring is substituted at either the para or meta positions [4‐Me, N∧N = 1 ; 4‐Br, N∧N = 2 ; 3,5‐Br 2 , N∧N = 3 ; 3,5‐(C 6 H 4 ‐4‐NPh 2 ) 2 , N∧N = 4 ]. The complexes have been fully characterized, and single‐crystal diffraction analyses of [Ir(ppy) 2 (N∧N)][PF 6 ] (N∧N = 1 – 3 ) confirmed that each [Ir(ppy) 2 (N∧N)] + cation exhibits face‐to‐face π‐stacking between the pendant phenyl substituent of the N∧N ligand and the cyclometallated phenyl ring of an adjacent [ppy] – ligand. In solution, the complexes are short‐lived emitters; the emission maxima for [Ir(ppy) 2 ( 1 )][PF 6 ], [Ir(ppy) 2 ( 2 )][PF 6 ], and [Ir(ppy) 2 ( 4 )][PF 6 ] are similar ( λ em = 600–608 nm), but the presence of the two bromo substituents in [Ir(ppy) 2 ( 3 )][PF 6 ] produces a redshift of ca. 30 nm. The solid‐state photoluminescent emission spectra of thin films of the complexes are similar to those in solution. The performances of the complexes as electroluminescent components in light‐emitting electrochemical cells (LECs) have been evaluated. The electroluminescence spectra show slight blueshifts with repect to the photoluminscence bands. LEC turn‐on times vary from instantaneous for N∧N = 2 to 2 h for N∧N = 1 . The device data suggest that the incorporation of Br substituents into the N∧N co‐ligand may not be beneficial.