"STR13## wherein R3 is CN, NO2, CF3, COOR5, COR5, SO2 OR5, SO2 R5, ##STR14## where R5 is an alkyl or an aryl and R6 is hydrogen, an alkyl or aryl group; X is hydrogen, halogen, OH, nitro or a monovalent organic group; n is 1 or 1 to 4 and when n is 2 or more each X may be the same or different; Y, which is optionally present, completes a 5- or 6-membered condensed ring; R4 is a divalent straight or" . . . . . .