Unexpected Luminescence Behavior of Coinage Metal π-Diborene Complexes

A number of unprecedented photophysical phenomena were observed in the study of luminescent pi-diborene complexes of Cu and Ag. These observations included unusually high fluorescence quantum yields (up to 100%) in solution for complexes of these metals. This result indicates that very little or no intersystem crossing between S-1 and T-n occurs in the complexes, despite the strong spin-orbit coupling of the metal atoms. The replacement of carbon with boron thus yields luminescent isolobal analogues of otherwise non-emissive olefin complexes of Cu and Ag.