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

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-P]}(+) 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 (MLLCT)-M-3 [d pi(Re) -> pi*(N-N)] phosphorescence at room temperature. The N-deprotonations of the benzoxazol-2-ylidene ligand in these complexes were investigated.