Disclosed is a compound of one of the formulae 1 2 wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 each, independently of the others, is an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group, R11 and R12 each, independently of the others, is an alkylene group, an arylene group, an arylalkylene group, or an alkylarylene group, G is a cationic moiety, A is an anionic moiety, n is an integer representing the number of repeat nullOSi(R7)(R8)null monomer units, a is an integer representing the number of repeat nullOSi(R10)(R12-lightfastness moiety)- monomer units, and c is an integer representing the number of repeat nullOSi(R9)(R11-hydrophilic moiety)- monomer units.