Determination of EPR parameters of gamma-irradiated powder limettin sample by experimental and theoretical studies

Limettin, also known as “citraptene”, is a dimethoxycoumarin (DMC), (C11H10O4), easily obtained from the sediment which is deposited from the expressed oil of limes1. In this study, the Limettin sample was irradiated for about 100 kGy total dose at room temperature by a 60Co-γ ray source. As a result of this irradiation, a stable radical has been obtained. In order to determine the produced radical experimentally, the spectra were taken at 0.1-20 mW microwave power and 123-393 K spectrometer temperature intervals. And experimental g values and hfccs of radical were determined. So we have modeled eight possible radical forms from two different stable conformations with approximately the same conformation energies. g values and hfccs of the model radicals were calculated with DFT/B3LYP using the TZVP basis set. As a result we compared the experimental and theoretically calculated values. Thus, we deduced that ĊH2(C9O2H4)OCH3, alkyl radicals (carbon centered) which are produced by abstraction of a single hydrogen atom were formed in the irradiated sample.