roup; or a 4-cyano-, 4-methoxy- or 4-dimethylamino-substituted phenyl group; R3 is H or a C1 -C8 -alkyl residue, R4 is an R3 group, cyano or a C1 -C10 -alkanoyl residue, or R3 and R4 jointly with the inclusion of N is a 5- or 6-membered heterocyclic ring wherein the ring can additionally contain a further heteroatom N, O, or S; R11 is a perfluorinated C1 -C4 -alkyl group; A and B either jointly ar