First subphthalocyanine analogue with fused 6H‐1,4‐diazepine ring and its conversion to aminobenzamide derivative.

Mixed cyclization of 5,7‐diphenyl‐6H‐1,4‐diazepine 2,3‐dicarbonitrile and tetrafluorophthalonitrile in the presence of boron trichloride affords along with symmetrical perfluorinated subphthakocyanine, [F₁₂sPc], two novel subporphyrazine‐type products which were isolated by column chromatography and characterized by mass‐sprectometry, NMR, IR, UV‐VIS and fluorescent spectroscopy. It was established that co‐cyclomerization of dinitriles is accompanied by electrophilic chlorination of 1,4‐diazepine ring by evolved Cl₂ resulting in formation of dibenzosubporphyrazine [F₈sPc1] with fused 6‐chloro‐5,7‐diphenyl‐6H‐1,4‐diazepine fragment. According to DFT modelling and ¹H NMR data, a more stable diastereomer with an axial Cl atom is formed and no inversion of the 1,4‐diazepine ring is observed. Hydrolytic cleavage of the 1,4‐diazepine fragment in [F₈sPc1] is observed upon chromatography or in the presence of a strong acid (CF₃COOH) and leads to 2‐amino‐3‐benzamide substituted dibenzo subporphyrazine [F₈sPc2]. Fluorescence of [F₈sPc1] (Φ_F=0.03) is ca 10 times lower than for [F₁₂sPc] (Φ_F=0.28) due to the combined effect of intramolecular charge transfer (ICT) from the donor diazepine ring to the acceptor sPc macrocycle and heavy atom effect of chlorine. Fluorescence of [F₈sPc2] is almost completely quenched by ICT from −NH₂ group to the electron‐deficient subporphyrazine core (Φ_F<0.001), but addition of acid leads to protonation of the amino group and switch‐ON the fluorescence. Therefore, aminobenzamide substituted subporphyrazines can be considered as perspective pH‐sensitive fluorophores.