Control of molecular orientation of 4,4′-bipyridinium cation radicals in novel photochromic monolayer assemblies

Abstract

The orientation of 4,4′-bipyridinum cation radicals, reversibly formed in novel photochromic monolayer assemblies of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate salts with N,N′-dihexadecyl-4,4′-bipyridinium and N-ethyl-N′-(2-ethylamide)-N″, N″-dihexadecyl-4,4′-bipyridinium ions via excitation of an ion-pair charge-transfer (CT) band (λ_ex.>365 nm), was controlled by the substituents of the 4,4′-bipyridinium ion.