Sulfaguanidine under UV irradiation in aqueous solution

The phototransformation of sulfaguanidine in water under ultraviolet (UV) radiation was studied experimentally and theoretically. Absorption, fluorescence and fluorescence excitation spectra of the studied substance before and after irradiation were obtained. Under the influence of KrCl excylamp radiation, stained photoproducts were formed. Quantum-chemical analysis of the orbital nature and localization of electronic transitions of complexes of photoproducts with water 1 : 3 reveals great similarity with the spectrum of the complex of the parent compound. The energy of electronic transitions of primary photoproducts decreases that is there is a low-energy shift of transitions $S_0\to S_1(\pi\pi)$ and $S_0\to S_3(\pi\pi)$ of the original molecule to long-wave region of spectrum (260–315 nm) and decrease of intensity of transition $S_0\to S_3(\pi\pi)$ of sulfaguanidine coplex. In the process of irradiation under the action of KrCl excylamp, the transformation of sulfaguanidine, its primary photoproducts and their subsequent interaction with each other and the solvent occur, which leads to the appearance of a colored photoproduct absorbing at $\lambda_{\mathrm{max}}$ = 560 nm.