Synthesis and characterization of novel bis-(4-methylcoumarin) derivatives as photosensitizers in antimicrobial photodynamic therapy

Abstract

Abstract Four coumarin derivatives were synthesized via the reaction of coumarin by four compounds namely 1,3-dibromopropane, 1,3-bis(bromomethyl)benzene, 1,4-bis(bromomethyl)benzene, and 2,6-bis(bromomethyl)naphthalene. The chemical structures of the prepared compounds were characterized by FTIR, 1H NMR and mass spectroscopy. The photophysical properties of the prepared compounds were determined by measuring the absorption and emission spectra. The photophysical properties of the prepared compounds were calculated such as: (e) molecular extinction coefficient; (σa) absorption cross section, (φf) fluorescence quantum yield, (τo) fluorescence life time, (f) oscillator strength, (Kisc) the intersystem crossing rate, (Kr) the radiative decay rate. The prepared compounds exhibited UV–vis absorption spectra in the absorption region of 250–350 nm with a maximum absorption peak at of 321 nm, and emission spectra were obtained in the range of 340–440 nm with different intensities depending on their chemical structures. In vitro microbiological investigation of the prepared coumarin derivatives in dark and UV irradiation was performed. All the compounds exhibited biocidal activities. Antimicrobial assay of the prepared compounds in dark showed their potency against the tested microorganisms. The antimicrobial assay in the presence of UV irradiation showed the photodynamic therapeutic activities of the coumarin derivatives. The photodynamic therapeutic activities were correlated to the photophysical properties of the tested compounds and their interaction by the cellular membranes.