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, C7H4F2N2 (I), and ethyl 4-amino-3,5-difluorobenzoate, C9H9F2NO2 (II), along with a visible-light-responsive azobenzene derivative, diethyl 4,4 '-(diazene-1,2-diyl)bis(3,5-difluorobenzoate), C18H14F4N2O4 (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 center dot center dot center dot N, N-H center dot center dot center dot F and N-H center dot center dot center dot O hydrogen bonds, C-H center dot center dot center dot F short contacts, and pi-stacking interactions. In crystal of III, only stacking interactions between the molecules are found.