Several 6-(4-nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-ene derivatives having various substituents on C 2 were synthesized, and their 1 H NMR spectra and photochromic behavior were examined.* The text was submitted by the authors in English.Study on photochromic materials has drawn great attention due to their applications in optical data storage devices, holographic storage, solar cells, and sensitizers [1,2]. Photochromism is a vast field encompassing well-known phenomena associated with reversible transformations upon irradiation with UV and visible light. In this chemical process, a compound absorbs electromagnetic radiation and undergoes a reversible change between two states that display different absorption spectra, i.e. different colors. In the recent time, various photochromic dyes have been developed to improve major photochromic properties such as reversibility and stability [3,4].We have recently become interested in photochromism and photoreproduction of 3,5-diazabicyclo-[3.1.0]hex-3-ene derivatives with various substituents [5]. In addition, synthesis of several fluorescence emission producers based on symmetrical and unsymmetrical trisannelated benzene constructions was attempted [6,7]. Applications of photochromic compounds directly depend upon color change produced by variation of the molecular and electronic structures in going from the initial to photoinduced form and their corresponding absorption or emission spectra. They can be used as variable-transmission optical materials for photochromic ophthalmic lenses or camera filters, fluid flow visualization, optical information storage, novelty items (e.g., toys, T-shirts, etc.), authentication systems (security printing inks), and cosmetics. Requirements for photonics devices are as follows: (1) thermal stability of both isomers, (2) low fatigue, i.e., the possibility for recycling without loss of performance, (3) repeatable cycle number > 10 4 , (4) high sensitivity (quantum yield > 0.5), (5) rapid response, (6) non-destructive readout capability, and (7) reactivity in the solid state. Among these, thermal stability and fatigue resistance are the most important.We recently used novel potentiometric membrane sensors based on 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diazabicyclo[3.1.0]hex-2-ene and 6-(4-nitrophenyl)-2-phenyl-4,4-dipropyl-3,5-diazabicyclo[3.1.0]hex-2-ene for detection of tin(II) [8] and strontium(II) ions [9], respectively, at trace levels in real samples. In the present article we report on several new photochromic compounds that are derivatives of well known photochromic 1,3-diazabicyclo[3.1.0]hex-3-ene system. Compounds I-XII with different substituents in the 2-position were synthesized following a slightly modified known procedure [10-14] (Scheme 1). Benzoylaziridines XV were prepared starting from chalcones XIII which were subjected to bromination at the double bond with bromine in chloroform solution to obtain dibromo derivatives XIV, followed by aziridination with a solution of ammonia in anhydrous ethanol at room tempe...