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-O]}⁺ and <i>cis</i>,<i>trans</i>-{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