First ion-pair charge-transfer complex showing a specific CT absorption spectrum with well-resolved vibrational structure in solution

An ion-pair charge-transfer complex showing a charge-transfer absorption spectrum with a well-resolved vibrational structure of about 1100–1400 cm−1 was first observed for the diquat (2,2′-bipyridinium) salt with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate in 1,2-dimethoxyethane solution at room temperature. It was ascribed to the highly ordered ternary complex of this ion pair in the less polar 1,2-dimethoxyethane solution.