present invention is concerned with compounds of formula i wherein n is 2 in another preferred embodiment the present invention is concerned with compounds of formula i wherein q is u2014 o u2014 in another preferred embodiment the present invention is concerned with compounds of formula i wherein m is 1 in another preferred embodiment the present invention is concerned with compounds of formula i wherein ar is phenylene in another preferred embodiment the present invention is concerned with compounds of formula i wherein r 5 is h in another preferred embodiment the present invention is concerned with compounds of formula i wherein r 6 is h in another preferred embodiment the present invention is concerned with compounds of formula i wherein r 7 is ethyl in another preferred embodiment the present invention is concerned with compounds of formula i wherein y is oxygen in another preferred embodiment the present invention is concerned with compounds of formula i wherein r 8 is h in the above structural formulas and throughout the present specification the following terms have the indicated meaning the terms u201c c 1 12 alkyl u201d as used herein alone or in combination is intended to include those alkyl groups of the designated length in either a linear or branched or cyclic configuration represents e g cyclopropyl cyclobutyl cyclopentyl cyclohexyl cycloheptyl and cyclooctyl and the like typical c 1 6 alkyl groups include but are not limited to methyl ethyl n propyl iso propyl butyl iso butyl sec butyl tert butyl pentyl iso pentyl hexyl iso hexyl cyclopropyl.