Luminescent charge-transfer complexes of 4,4′-bipyridinium ion with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion

Abstract

4,4′-bipyridinium ions form ion-pair charge-transfer (CT) complexes with tetrakis[3,5-bis(trifluoromethyl)phenyl] borate anion with a discrete absorption maximum at 420 nm in methanol and at 475 nm in 1,2-dimethoxyethane. These CT complexes in 1,2-dimethoxyethane at 20°C show broad structureless luminescence with a maximum at 553 nm, almost a mirror image of the CT absorption spectrum. The luminescence could not be observed for CT complexes in methanol. This is the first observation of luminescence from excited ion-pair CT complexes in solutions at room temperature.