Synthesis and photochromic properties of a new functionally substituted molecule based on spiropyran.

Bistable compounds capable of reversible molecular rearrangements between two nonequivalent states are of great interest for the creation of new materials and the study of many chemical and biological processes that are used in modern technologies. One of the most studied mechanisms of the functioning of such bistable systems is photochromism - a change in the structure and spectral properties of compounds under the influence of external factors. Among the most studied classes of organic photochromic structures are spirocyclic compounds, such as spiropyrans, which are capable of switching between the usually colorless cyclic and colored merocyanine forms when exposed to external stimuli such as light, temperature, pressure, polarity, mechanical stress, electric or magnetic field, which allows their use in memory elements, as optoelectronic devices, sensors, etc.

The choice of spiropyrans as model compounds of this class of photochromic molecules is not accidental, since they are the most well-known and unique representatives of photochromic compounds due to the relative ease of their preparation, structural modification and the possibility of targeted changes in spectral and kinetic characteristics over a wide range. The isomeric forms of spiropyrans differ significantly in their physical and optical properties, which makes them very promising compounds for use in various fields of science and technology.

In this work, we report the synthesis of a new salt of photochromic spiropyran containing various functional groups (-CHO, -NO₂, -OCH₃, -(CH₂)₅PPh₃), capable of reversibly responding to external influences. Photoinduced transformations, spectral and kinetic characteristics of the synthesized compound were studied.