Conformational study of caffeic acid derivatives

The conformational analysis of six tripodal caffeic acid derivatives is obtained through semiempirical (AM1 and PM3) and Density Functional Theory (B3LYP/DZVP2, in this case) calculations. It was found that structures with small tripodal sides (n = 1) are mainly stabilized by π electron delocalization. In contrast, intramolecular hydrogen bonds play a very important role in the stabilization of structures with larger tripodal sides (n = 2), where hydrogen bonds restrain the degrees of freedom of the structure. It was also found that another important aspect in the conformational search is the symmetry (C3, in this case), since symmetrical structures were energetically preferred to those that are not symmetrical.