ИСТИНА

One of the most important directions of supramolecular photochemistry is molecular design, synthesis, and study of physicochemical properties of photochromic compounds. At the same time, intensive studies of recent decades in the field of organized molecular ensembles (monolayers on the liquid surfaces, Langmuir-Blodgett films (LBF), self-assembled adsorption layers) have made a significant contribution to the development of the principles of creating molecular devices and functionalized surfaces. With the development of ultra-thin optoelectronic devices, monolayers based on photochromic materials are attracting increasing attention as building blocks for the operational mechanisms of these systems. In this connection, at present, studies of Langmuir monolayers of photochromic compounds are aimed at establishing a connection between the structural organization of these systems and the efficiency of photochemical transformations in them. The most important class of organic photochromes are spyropyrans and their derivatives, spyronaphthoxazines (SNO), which possess high thermal stability, a narrow absorbance band, and exhibit photochromic properties in solutions, polymeric matrices, and self-assembled monolayers. However, the properties of spyronaphthoxazines in monolayers and LBFs have not been yet studied. In this work, we present the results of studying the photochromic properties of SNO films at the air/water interface by means of Langmuir monolayer method and fiber optic spectrophotometry. Comparative studies of the photochromism of spyro[indolino-2,3'-[3h]naphtho[2,1-b]-[1,4]oxazine (SINO-18) in solutions and at the interface were carried out. The kinetic regularities of phototransformations of this compound under UV irradiation and dark relaxation are revealed. It is established that spyronaphthoxazine retains its photochromic properties both in solutions and two-dimensional condensed state. The phenomenon of the photomechanical effect in monolayers of SINO-18 was revealed and studied: under the influence of UV irradiation, the system undergoes reversible transitions from the closed spyro form to the open merocyanine one, which is accompanied by a change in the surface pressure of the monolayer. This fact indicates the potential employment of monolayers based on spyronaphthoxazines as operational elements of molecular mechanisms.