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)2Ir(μ-Cl)2Ir(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, 1H 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 expected bidentate chelation of cyclometallating ligands (phquinox) against our previous report of an ortho CH 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 unexceptional 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.