Pyridine aldoxime ligation to iridium(III) centre: An innocent ancillary ligand in a series of organometallic complexes

Abstract

A series of Ir(III) complexes ( 4 )-( 6 ) of formula [Ir(C <^> N)(2)(pyrald)] were designed and synthesised from the reaction of [(C <^> N)(2)Ir(mu-Cl)(2)Ir(C <^> N)(2)] and pyridine-2-aldoxime (pyrald) {C <^> N = 1-phenylpyrazole (phpyr), 2,5-diphenylbenzoxazole (phox) and 2,3-diphenylquinoxaline (phquinox)}. All the complexes were purified on a neutral alumina oxide column and characterised through IR, 1 H NMR, UV-Vis, emission spectroscopy, mass analysis and cyclic voltammetric studies. The molecular structure of [Ir(phquinox)(2)(pyrald)](6) was determined using single crystal X-ray data analysis, which presents an ex-pected bidentate chelation of cyclometallating ligands (phquinox) against our previous report of an ortho C -H bond activation in a coordinated cyclometallating ligand (7,8-benzoquinoline) mediated by pyridine-2-aldoxime. The characterisation data of complexes ( 4 ) and ( 5 ) are also in agreement with the unexcep-tional coordination behaviour of coordinating ligands. On TD-DFT calculations, all the complexes revealed the dominant ligand centred (LC) transitions and were reasoned for observed weak luminescence. (C) 2022 Elsevier B.V. All rights reserved.