Ab initio and DFT conformational analysis of selected flavones: 5,7-dihydroxyflavone (chrysin) and 7,8-dihydroxyflavone

Ab initio and DFT conformational analysis was performed on the flavone derivatives chrysin (5,7-dihydroxyflavone; 2-phenyl-5,7-dihydroxy-4H-1-benzopyran-4-one) and 7,8-dihydroxyflavone (2-phenyl-7,8-dihydroxy-4H-1-benzopyran-4-one). The structural features required for optimal stabilization in each molecule were identified. It was discovered that sparsely placed hydroxyl groups, particularly with hydrogen bond-like interactions, resulted in lowering the potential energy minimum for the molecules. It was also noted that one of the factors capable of destroying co-planarity was steric interference between closely placed functional groups across the phenyl and the benzo-γ-pyrane ring. Studies performed on the radical forms of the flavonoids, however, showed that the unpaired electron is confined only to the benzo-γ-pyrane ring, and not delocalized across the phenyl ring.