ИСТИНА

The steady interest for studies of photochromic properties of monolayers and ultrathin films of optically active compounds at interfaces is due to intensive development of molecular electronics, microsensorics, production of optical memory devices, etc. At the same time, Langmuir monolayer method and Langmuir-Blodgett (LB) technique provide possibility for assembly of multilayered planar structures with controllable film thickness and molecular orientation in the layers. The ability to control the properties of LB films via external stimuli is one of the key moments in development of molecular machines and mechanisms, nano-devices, ultrathin optoelectronics, etc. One of the most important classes of organic photochromes is spyropyrans, which attract intensive interest of researchers due to their ability of molecular switching. Due to this facts, in the present work, optical and physico-chemical properties of solutions of novel amphiphilic spyropyran (SP1) and Langmuir monolayers on its basis are studied by means of absorbance spectroscopy, fiber optic spectrophotometry and Langmuir monolayer method. It is established that SP1 in spyro form does not form stable monolayers at air/water interface, while its merocyanine form can be completely spread on the water surface and forms true monolayer with a collapse pressure around 45 mN/m. This can be due to the fact that the studied photochrome in merocyanine form possesses pronounced amphiphilic properties, while closed spyropyran form is totally hydrophobic, and this compound molecules most likely form unorganized polymolecular clusters upon increase of surface pressure. Moreover, it was shown, that upon transition from soluted state into planar one, tendency of SP1 to form J-type aggregates sharply increases, which is confirmed by appearance and increase of absorbance band around 620 nm. Dilution of SP1 molecules by cetyl alcohol allows one to decrease the aggregation degree of this compound in the monolayer and to achieve complete spreading of the spyropyran on the water surface with simultaneous retention of photochromic properties of the substance in planar state. Thus, a principal possibility for employment of spyropyran derivatives as operational elements of molecular mechanisms is shown.