Study on the Effect of Bromation on Molecular Properties of Hypocrellin by Quantum Chemistry

Thesemi-empirical quantum chemistry method AM1 and PM3 were used to calculate the molecules of hypocrellin B and its substitutes by bromine,the effect of bromation on the properties of hypocrellin B were also investigated.The results which obtained from AM1 and PM3 calculations showed that the heat of formation,HOMO or LUMO energy levels and dipole moment of all isomers of hypocrellin B are all lowed to a certain extent due to bromation.At the same time,the property of intramolecular hydrogen bond is changed and the wavelengths of light absorbed are increased for all substitutes of hypocrellin B by bromine according to AM1 and PM3 calculations.