Synthesis, molecular and crystal structures of 4-amino-3,5-difluorobenzonitrile, ethyl 4-amino-3,5-difluorobenzoate, and diethyl 4,4′-(diazene-1,2-diyl)bis(3,5-difluorobenzoate)

The crystal structures of two intermediates, 4-amino-3,5-difluorobenzonitrile, C 7 H 4 F 2 N 2 ( I ), and ethyl 4-amino-3,5-difluorobenzoate, C 9 H 9 F 2 NO 2 ( II ), along with a visible-light-responsive azobenzene derivative, diethyl 4,4′-(diazene-1,2-diyl)bis(3,5-difluorobenzoate), C 18 H 14 F 4 N 2 O 4 ( III ), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The molecules of I and II demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 ( ortho ) positions. In the crystals of I and II , the molecules are connected by N—H...N, N—H...F and N—H...O hydrogen bonds, C—H...F short contacts, and π-stacking interactions. In crystal of III , only stacking interactions between the molecules are found.