Spectroscopic Studies on the Molecular Complex of the Drug Atenolol with Iodine

Spectroscopic and spectrofluorimetric studies were made of the interaction between the drug atenolol and iodine. The interaction was found to proceed through the initial formation of a charge transfer (CT) complex as an intermediate species. The product of this interaction has been isolated and characterized using UV-Vis, FT-IR and Raman spectroscopic techniques. Formation of the triodide \(\mathrm{I}_{3}^{-}\) species was confirmed by its electronic and Raman spectra. Peaks appeared in Raman spectrum of the isolated product at 153, 102 and 85 cm−1 that are assigned to ν as(I-I), ν s(I-I) and \(\delta(\mathrm{I}_{3}^{-})\) respectively, which confirmed the presence of the \(\mathrm{I}_{3}^{-}\) ion. The stoichiometry of the complex was found to be 1:2. The rate of their reaction has been measured as a function of time and solvent. Pseudo-first-order rate constants for the reaction were measured at various temperatures and the thermodynamic activation parameters (ΔG #,ΔS # and ΔH #) were computed. Preliminary fluorescence quenching studies indicated that the interaction between atenolol and iodine is spontaneous and proceeds through a CT complex, and the quenching of fluorescence of atenolol by iodine increases as the extent of such complexation increases