Media and solute–solvent interaction effects on the photo–physical behavior of some drugs of 4H–Pyran derivatives

Abstract

In this work, spectral properties of four 4H–Pyran derivative compounds, (Pyran (I), Pyran (II), Pyran (III) and Pyran (IV)) which are used as drugs in the treatment of some diseases have been studied in various solvents with different polarities. As expected, the results indicate that photo–physical behavior of solute depends strongly on the nature of the solvent and solute, the solvent–solute interactions, and also different attached groups on their structures. Beside these aspects, delocalization of π electrons within various resonance forms of these molecules also found to be an important factor. The solvatochromic behavior of these drug materials and their solvent–solute interactions, both specific and non–specific types were analyzed by means of linear solvation energy relationships, suggested by Kamlet and Taft. Also, vertical excitations of studied molecules were studied by time dependent density functional theory. The ground and excited state dipole moments of these drug materials and their molecular resonance structures were also evaluated via solvatochromic shift method. Both of the experimental data and quantum chemical calculations confirm higher polarities of excited states of these molecules compared to their ground states. Moreover, calculations of the density functional theory propose a charge transfer from the ends of mentioned molecules toward their –CN terminals throughout the excitation process.