The invention disclosed relates to functionalized zwitterionic chromophores of structural formula III and III′.
Wherein A is a linear or branched alkyl group having up to 20 carbon atoms and the desired functional groups, B is hydrogen, alkyl, aryl, halo, heterocyclic, alkoxy or nitro groups at 2, 3, 5 or 6 positions on the pyridine ring, C is hydrogen, aryl or a linear or branched alkyl group at 2′, 3′, 5′ or 6′ positions on the benzene ring, which has up to 70 carbon atoms and contains the desired functional group, D is a linear or branched alkyl, aryl or substituted aryl group, which has up to 70 carbon atoms and contains the desired functional group, R is C1-C4 alkyl or aryl, and m is an integer of from 0 to 4.