Study of absorption of tetrahydrophenanthridine hydroxynitrostyrils

Abstract

These dyes also include a series of compounds based on phenanthridine, the derivatives of 10-(2'-oxo-5'-nitrobenzylidene)-tetrahydrophenanthridine (PS) (Fig. I), which under the action of light irreversibly change their color, and are proposed as materials for photochemical recording of information in silverless photography [4]. In a study of the nature of the photochemical transformations of PS, it was found that they have a whole series of other interesting properties, such as a strong dependence on the color of the solution on the nature of the solvent (solvatochromism), a reversible change in the color of the solution with change in acidity (protonation) and temperature (thermochromism), the presence of prolonged phosphorescence, a strong dependence of the photoluminescence spectra on the wave length of the exciting light, which cannot be explained by the presence of impurity and other experimental conditions. The aim of the present investigation is to clarify these phenomena and their possible practical utilization. In the present work, we submit some of the results relating to the absorption spectra of PS. The dependence of the spectra on the structure of the molecule is analyzed, the influence of the polarity of solvents and the acidity of the solution on the absorption spectra is studied, and the experimentally obtained energies of electronic transitions are compared with calculated ones within the scope of the quantum-chemical approximations. Conclusions are drawn on the nature of the individual absorption bands in the spectra of PS. The compounds are synthesized in two stages. The first stage consists in the synthesis of quaternary salt of tetrahydrophenanthridine by reacting a secondary amine with a mixture of formaldehyde and cyclohexanone in the presence of perchloric acid [5]. At the second stage, the salt obtained reacts with5-nitrosalicylaldehyde in a mixture of butanol and pyridine. As a result of the reaction, a compound is formed in the form of a red-brown finely crystalline powder, which is readily soluble in alcohols and ketones and poorly soluble in water. For the investigation, solutions of the compounds in liquid solvents and polymeric matrices were used. These were obtained by preliminarily holding a swollen film of cellulose acetobutyrate in solutions of PS compounds. To measure the IR spectra, samples were prepared in the form of tablets pressed under a pressure of 2.107 Pa from a thoroughtly mixed 100:1 mixture of KBr with the compound studied.