Diastereoselective Formation and Photophysical Behavior of a Chiral Copper(I) phenanthroline Complex

The Friedländer condensation of (1R,5S)-(+)- and (1S,5R)-(-)-nopinone with 8-aminoquinoline-7-carbaldehyde leads to the corresponding enantiomerically pure (2,3-b)-pineno-1,10-phenanthrolines. Coordination of these ligands with Cu(I) affords non-interconvertable chiral complexes which show equal and opposite Cotton effects in their CD spectra as well as identical half-wave oxidation potentials of +0.37 V and identical MLCT absorptions at 442 nm. Both complexes are nonemissive at 298 and 77 K. Stern-Volmer quenching studies were carried out with optically pure Δ- and Λ-[Ru(bpy)3]2+ and racemic [Ru(dpb)3]2+ as donors (bpy = 2,2′-bipyridine and dpb = 4,4′-diphenyl-bpy). Neither study provides any evidence of enantioselective quenching, indicating that energy or electron transfer may be occurring through a distance where chiral recognition is unimportant.