Patent ID: 7112674

Claim:
A 2,5-diaminoterephthalic acid derivative of formula 19, wherein X 1 and X 3 are O, X 2 and X 4 , which can be the same or different, are O or N; R 2 and R 6 are methylene (—CH 2 —), which can be substituted with trifluoromethyl, R 3 and R 7 are the same or different, H, C 1 –C 8 alkyl, aryl, or heteroaryl, and R 4 and R 8 are the same or different, H, alkyl, aryl or trifluoromethyl, and R 1 and R 5 , which can be the same or different and are H, C 1 –C 4 alkyl or phenyl with the proviso that R 1 is absent if X 2 is O and R 5 is absent if X 4 is O.