. . . . . "form an aromatic or aliphatic ring, and ##STR14## in which R12 and R13 are identical or different and are a hydrogen atom, a halogen atom, a C1 -C10 -alkyl group, a C1 -C10 -fluoroalkyl group, a C6 -C10 -aryl group, a C6 -C10 -fluoroaryl group, a C1 -C10 -alkoxy group, a C2 -C10 -alkenyl group, a C7 -C40 -arylalkyl group, a C8 -C40 -arylalkenyl group or a C7 -C40 -alkylaryl group, or R12 and R13," . . . .