NEUTRON INELASTIC-SCATTERING AND DENSITY-FUNCTIONAL CALCULATIONS FOR ANALYZING THE FORCE-FIELDS OF HYPERICINE MODEL COMPOUNDS - ANTHRONE AND BIANTHRONE

Neutron inelastic scattering (NIS) spectroscopy has been used to analy se the solid phase and low temperature vibrational features of two ant iviral agents, anthrone and bianthrone, which belong to a group of mol ecules whose main member is hypericin. The vibrational wavenumbers of anthrone and bianthrone obtained from NIS spectra have been compared t o those previously observed in FT-Raman spectra recorded in the solid phase at room temperature, From the experimental point of view, the ex istence of the anthrone skeleton in the chemical constitution of both molecules leads to the similarity of their vibrational features, This facilitates considerably the interpretation of their vibrational spect ra. In order to reinforce the vibrational mode assignment of these mol ecules, quantum mechanical calculations based on the density functiona l theory (DFT) have been undertaken initially on anthrone. To improve the agreement between the calculated and experimental results, the mol ecular force field has been scaled using the Pulay method. (C) 1997 El sevier Science B.V.