Cation-dependent pericyclic reactions of crown-containing photochromic compounds

The review is devoted to the photochromism of pericyclic reactions of crown-containing photochromic systems. The complex formation of photochromic crown ethers with metal cations has a substantial effect on both the spectral characteristics of molecules and occurrence of photochromic reactions. A possibility to create systems with photocontrolled complex-forming properties is an attractive feature of the novel systems.     

Crown-containing spironaphthoxazines and spiropyrans. 2. Influence of metal cations on the photochromic properties of spironaphthoxazines linked with aza-15(18)-crown-5(6) ethers

Spironaphthoxazines linked with aza-15(18)-crown-5(6) fragments were synthesized and studied for the first time. Addition of alkaline-earth cations to solutions of crown-containing spironaphthoxazines causes a hypsochromic shift of the absorption band of the spiro form and a bathochromic shift of the absorption band of the merocyanine form, shifts the equilibrium to the merocyanine form, and changes the lifetime of the photoexcited merocyanine form. The spectral and kinetic data were used to propose a mechanism of complexation and calculate the stability constants of the resulting complexes. The complexation involves the crown fragment and the merocyanine oxygen atom. The type of the complex is determined by the cation nature and size.     

Bromination of photochromic spironaphthoxazines

Direct bromination of photochromic compounds of the spironaphthoxazine and spironaphthopyran series was performed using N-bromosuccinimide to obtain both photochromic bromine-substituted spiro compounds and nonphotochromic 2-(naphtho[1,2-d]oxazol-2-yl)-3H-indolium bromides. The structures of the resulting products were established by NMR spectroscopy and mass spectrometry. The mechanism of bromination taking into account the involvement of both closed and open (colored) forms of spiro compounds was proposed.     

Synthesis and properties of a novel photochromic luminophore

A photochemically bifunctional compound was obtained. Its molecule includes the spironaphthoxazine and dansylamino fragments. This compound exhibits both photochromic and luminescent properties. Its spectroscopic characteristics were studied in different solvents. The electronic systems of two constituent fragments do not interact with each other. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2802–2805, December, 2005.     

Merocyanine form of photochromic spirooxazines in acid solutions

Electronic absorption and NMR spectra of solutions of photochromic spironaphthoxazines (SNOs) were studied. The addition of an acid results in the formation of a salt of the colored form of SNO. For SNOs with nitrogen-containing electron-releasing substituents, the structure of the product that formed depends on the acid concentration being the salt of the mono- or dication.