Preferred compounds of formula (I) include those wherein Z is a covalent bond, Y is H, R3 is ClCH2CH2 or ethyl, R5 or R6 is iodo, R4 is H or with R3 is ???CH2CH2??? or ???S???, R1 and R2 are each CH3 or together with N are pyrrolidino, hexamethyleneimino or piperidino.