Competition Between the Intramolecular Hydrogen Bond and the π-Electron Delocalization in Some RAHB Systems: A Theoretical Study

Abstract

In the present study, the competition between the intramolecular hydrogen bond (IMHB) and the π-electron delocalization (π-ED) in some derivatives of triformylmethane (TFM) are investigated. In this regard, all of the hydrogen bonded structures are optimized by B3LYP and MP2 methods with the 6-311++G(d,p) basis set. The relative energies clearly predict that the B conformers (cis and trans) are more stable than the A and C ones; B < A < C. This order can be related to their IMHB strength and π-ED. Accordingly, IMHB and π-ED of all hydrogen bonded structures are comprehensively investigated. The IMHB results show that the O™H ⋯ O unit of A conformers is stronger than the corresponding interactions of other forms and is not consistent with the stability order. On the other hand, the π-electron delocalization of B forms are greater than those of A and C ones, which strongly support the stability order. Consequently, in the benchmark systems, the π-electron delocalization is a superior factor in determining the most stable structures.