The photodimerization of Schiff bases: Synthesis and crystal structures of benzophenone azines and their weak C–H···π interactions

Four benzophenone azines were synthesized through a photodimerization process. The crystals are constructed through weak C–H⋯π packing interactions, with additional π···π stabilization in two of the crystals. The four intermediates of the photodimerization process were also crystallized and their crystal structures are discussed. The packing of three of these intermediates involves weak C–H⋯O interactions. The crystal structure of di-isoniazid azine, an expected by-product of the photodimerization process, is also described.