MEPhI scientists as part of an international scientific group, using computer simulation, proposed and then synthesized a series of highly soluble solvatochromic dyes. These substances can be used as indicators of the polarity of solutions, as well as for fluorescent diagnostics and photodynamic therapy of cancerous tumors.

Solvatochromic molecules change their color depending on the solvent they are in. Thanks to them, you can "see" such characteristics of the solution as polarity or acidity. Their secret is quite simple: they have several similar energy forms that have different electronic structures and therefore interact differently with light. Depending on the environment, one form or another may prevail. In addition, hydrogen bonds with solvent molecules and "shielding" of the electron density of the dye in solution play an important role. The dyes synthesized as part of the study are soluble in almost all organic solvents and have demonstrated strong solvatochromic properties.

The new molecules are a hybrid based on two well-known dyes. “The first of these is fluorene, which underlies many photosensitizers, sensors, fluorescent indicators and light-emitting materials. Its main advantage is a flat structure and high rigidity combined with an abundance of aromatic rings. The second "parent" of the new molecule was the arylazo group, on the basis of which hair and fabric dyes are made, as well as ink for inkjet and laser printers. As a result, we managed to find a fairly simple way to synthesize a series of hybrid solvatochromic dyes and study their behavior in different solvents,” said Konstantin Katin, one of the authors of the study, professor of the MEPhI.

New molecules can be used as indicators of the polarity of solutions. Now the authors of the study are working on their adaptation for photosensitization of biological tissues - that is, increasing the sensitivity of tissues to light exposure. This will make it possible to use such molecules for fluorescent diagnostics and photodynamic therapy of cancerous tumors.

“In our study, the role of computer simulation is very important. Synthesizing a "good" molecule without the help of a computer is as difficult as finding a golden grain of sand in a pile of ordinary sand. Our molecules were found as a result of many calculations; only after that it was possible to synthesize and characterize them,” said Konstantin Katin.

To date, dyes have been successfully synthesized, and their properties have been experimentally studied using IR, UV, and visible spectroscopy, as well as theoretically explained within the framework of the time theory of the electron density functional and several semi-empirical models. A strong shift of the spectra in various organic solvents has been experimentally proven (9 solvents were considered, including ethanol, acetone, chloroform, dimethyl sulfoxide, etc.). The results are published. Computer modeling is currently underway to find suitable carriers that could deliver the obtained dyes to various types of tumors and efficiently accumulate in them.

The main result of the study can be considered that a simple method has been found for the synthesis of new dyes from available and inexpensive precursors. The resulting dyes combine the advantages of two well-known families of dyes, since they simultaneously contain fluorene and an arylazo group. In addition, they are readily soluble in almost all organic solvents and exhibit strong solvatochromic properties. The authors of the study expect that, after appropriate modification, they will become effective photosensitizers suitable for use in photodynamic therapy.

Research involves four stages: computer modeling, synthesis and study of physicochemical properties, in vitro studies of biochemical properties and testing of new substances on living organisms. Interaction with healthcare professionals is essential at the last stage of the study. Scientists already have a positive experience of working with a hospital in Tabriz (Iran), which has successfully tested our adsorbents on patients.

The project is supported by the Priority 2030 program.

The results of the study were published in Journal of Molecular Liquids (https://linkinghub.elsevier.com/retrieve/pii/S0167732223009224).