A compound selected from the group consisting of G6, G7, G8, and G9 with the following structures: and wherein each R is independently substituted or unsubstituted-(C 1 -C 6)alkyl-, substituted or unsubstituted -(CH 2) n O(C 1 -C 6)alkyl-, substituted or unsubstituted-(CH 2) n C -, substituted or unsubstituted-(CH 2) n C (C 1 -C 6)alkyl-, substituted or unsubstituted- (CH 2) n C O(C 1 -C 6)alkyl-, substituted or unsubstituted -(CH 2) n NH(C 1 -C 6)alkyl-, substituted or unsubstituted-(CH 2) n C NH(C 1 -C 6)alkyl-, substituted or unsubstituted- (CH 2) n S(C 1 -C 6)alkyl-, substituted or unsubstituted-(CH 2) n C (CH 2) n S(C 1 -C 6)alkyl-, substituted or unsubstituted-(C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n O(C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n C (C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n C O(C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n NH(C 1 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n C NH(C 2 -C 6)alkenyl-, substituted or unsubstituted -(CH 2) n S(C 2 -C 6)alkenyl-, substituted or unsubstituted -(CH 2) n C (CH 2) n S(C 2 -C 6)alkenyl-, substituted or unsubstituted -(C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n O(C 2 -C 6)alkynyl-, substituted or unsubstituted- (CH 2) n C (C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n C O(C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n NH(C 1 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n C NH(C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n S(C 2 -C 6)alkynyl-, substituted or unsubstituted -(CH 2) n C (CH 2) n S(C 2 -C 6)alkyynyl-, wherein each alkyl, alkenyl and alkynyl group is optionally substituted with alkyl, alkoxy, amino, carboxyl, cyano, nitro, or trifluoromethyl, and each n is independently an integer selected from 0, 1, 2, 3, 4, 5, and 6. wherein each R is independently substituted or unsubstituted-(C 1 -C 6)alkyl-, substituted or unsubstituted -(CH 2) n O(C 1 -C 6)alkyl-, substituted or unsubstituted-(CH 2) n C -, substituted or unsubstituted-(CH 2) n C (C 1 -C 6)alkyl-, substituted or unsubstituted- (CH 2) n C O(C 1 -C 6)alkyl-, substituted or unsubstituted -(CH 2) n NH(C 1 -C 6)alkyl-, substituted or unsubstituted-(CH 2) n C NH(C 1 -C 6)alkyl-, substituted or unsubstituted- (CH 2) n S(C 1 -C 6)alkyl-, substituted or unsubstituted-(CH 2) n C (CH 2) n S(C 1 -C 6)alkyl-, substituted or unsubstituted-(C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n O(C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n C (C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n C O(C 2 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n NH(C 1 -C 6)alkenyl-, substituted or unsubstituted-(CH 2) n C NH(C 2 -C 6)alkenyl-, substituted or unsubstituted -(CH 2) n S(C 2 -C 6)alkenyl-, substituted or unsubstituted -(CH 2) n C (CH 2) n S(C 2 -C 6)alkenyl-, substituted or unsubstituted -(C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n O(C 2 -C 6)alkynyl-, substituted or unsubstituted- (CH 2) n C (C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n C O(C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n NH(C 1 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n C NH(C 2 -C 6)alkynyl-, substituted or unsubstituted-(CH 2) n S(C 2 -C 6)alkynyl-, substituted or unsubstituted -(CH 2) n C (CH 2) n S(C 2 -C 6)alkyynyl-, wherein each alkyl, alkenyl and alkynyl group is optionally substituted with alkyl, alkoxy, amino, carboxyl, cyano, nitro, or trifluoromethyl, and each n is independently an integer selected from 0, 1, 2, 3, 4, 5, and 6.