The present invention is directed to compounds represented by the formula I: wherein R.sub.1 comprises a hydrogen atom or an alkyl group having 1 to 2 carbon atoms; wherein R.sub.2 comprises an alkylene group, an arylene group, or a heterocyclic group; and wherein R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, and R.sub.8 are identical or different and comprise a hydrogen atom, an alkyl group, an aryl group, or an alkylaryl group.

The present invention is directed to compounds represented by the formula (I): wherein R.sub.1 comprises a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, wherein R.sub.2 comprises an alkylene group, an arylene group, or a heterocyclic group. The three R.sub.2 groups may be the same or different, wherein A comprises an alkyl, an aryl, or an alkylaryl group. The three A groups may be the same or different. ##STR00001##