Compounds of the formulae ##STR00001## wherein Z is --OR.sub.1, --SR.sub.1, --NR.sub.1R.sub.2, Y is --OR.sub.3, --SR.sub.3, or --NR.sub.3R.sub.4, at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 is hydrogen, at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 is other than hydrogen, at least one Z or Y within the compound is --NR.sub.1R.sub.2 or --NR.sub.3R.sub.4, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, and R.sub.7 each, independently of the others, is hydrogen, alkyl, aryl, arylalkyl, or alkylaryl, and wherein R.sub.7 can also be alkoxy, aryloxy, arylalkyloxy, alkylaryloxy, polyalkyleneoxy, polyaryleneoxy, polyarylalkyleneoxy, polyalkylaryleneoxy, silyl, siloxane, polysilylene, polysiloxane, or ##STR00002## wherein X is a direct bond, oxygen, sulfur, --NR.sub.40-- wherein R.sub.40 is hydrogen, alkyl, aryl, arylalkyl, alkylaryl, or --CR.sub.50R.sub.60-- wherein R.sub.50 and R.sub.60 each, independently of the other, is hydrogen, alkyl, aryl, arylalkyl, or alkylaryl.