Luminescent Rhenium(I) Phenanthroline Complexes with a Benzoxazol-2-ylidene Ligand: Synthesis, Characterization, and Photophysical Study

Abstract

A series of luminescent rhenium(I) phenanthroline complexes containing benzoxazol-2-ylidene ligands with the general formula {Re(CO)3(phen)[CN(X)C6H4-2-O]}+ and cis,trans-{Re(CO)2(phen)(L)[CN(H)C6H4-2-O]}+ (X = H, methyl; phen = 1,10-phenanthroline; L = PPh3, PPh2Me, P(OEt)3) have been synthesized and characterized. The X-ray crystal structures of most of the carbene complexes and some of their synthetic precursors have also been determined. A new synthetic methodology for the preparation of dicarbonyl rhenium diimine synthetic precursors with a labile acetonitrile ligand, [Re(CO)2(phen)(PR3)(MeCN)]+, was developed. Photophysical study shows that these carbene complexes display a green to red 3MLLCT [dπ(Re) → π*(N–N)] phosphorescence at room temperature. The N-deprotonations of the benzoxazol-2-ylidene ligand in these complexes were investigated.