group having 1 to 4 carbon atoms, R5 is an alkyl substituent having from 1 to 4 carbon atoms, and p is an integer from 1 to 4, (e) --SR6 where R6 is an alkyl substituent having from 1 to 6 carbon atoms, (f) --NH2, (g) --NHR7 where R7 is an alkyl substituent having 1 to 6 carbon atoms, (h) --NR8 R9 where R8 and R9 are independently chosen from alkyl substituents having 1 to 6 carbon atoms, ##STR12