{HEAD ~ A compound} of the formula: ##STR35## wherein R1 is C1 C6 lower alkyl, C1 C6 alkylthio, C6 C10 aryl, C7 C16 arylalkyl, C6 C10 arylthio, C7 C16 arylalkylthio, cyano, C1 C6 perfluorinated lower alkyl, or ##STR36## wherein R is {TAIL ~ a chain} of 1 5 carbon atoms; and R2, R3, and R4 are each independently: 
{ HEAD ~ A compound } of the formula : # # STR35 # # wherein R1 is C1 C6 lower alkyl , C1 C6 alkylthio , C6 C10 aryl , C7 C16 arylalkyl , C6 C10 arylthio , C7 C16 arylalkylthio , cyano , C1 C6 perfluorinated lower alkyl , or # # STR36 # # wherein R is { TAIL ~ a chain } of 1 5 carbon atoms ; and R2 , R3 , and R4 are each independently :
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH