Synthesis, mol-ecular and crystal structures of 4-amino-3,5-di-fluoro-benzo-nitrile, ethyl 4-amino-3,5-di-fluoro-benzoate, and diethyl 4,4'-(diazene-1,2-di-yl)bis-(3,5-di-fluoro-benzoate).

The crystal structures of two inter-mediates, 4-amino-3,5-di-fluoro-benzo-nitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-di-fluoro-benzoate, C9H9F2NO2 (II), along with a visible-light-responsive azo-benzene derivative, diethyl 4,4'-(diazene-1,2-di-yl)bis-(3,5-di-fluoro-benzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The mol-ecules 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 mol-ecules are connected by N-H⋯N, N-H⋯F and N-H⋯O hydrogen bonds, C-H⋯F short contacts, and π-stacking inter-actions. In crystal of III, only stacking inter-actions between the mol-ecules are found.