Investigation of the Jahn-Teller Effect on Intramolecular Hydrogen Bonding in Dimer Compounds of Methanoic Acid and Analog Containing S and Se Atoms

Based on the studies in the field of chemicals and the origin of the equilibrium geometric structure, any system tends to reach its stable state. Therefore, the unstable states of molecular systems with high symmetry configuration are inclined toward low symmetry and become stable. This effect is an important factor in the symmetry breaking of the molecules and solid-state systems. The vibronic coupling between the base and excited states along the core movements are assumed as distortions that alter the configuration of the system from a high-symmetry flat geometric structure to a low-symmetry distorted equilibrium structure with low symmetry. The distortion significantly affects the prediction of the systems’ molecular spectrum and molecular properties, as the electrical, magnetic, and conductance properties, as well as other properties, can be changed. Based on what was said, the current study aimed to investigate the Pseudo Jahn-Teller Effect (PJTE) on the distortion of hydrogen bonding of dimmer compounds of Methanoic acid and the analog containing the S and Se atoms. The results show that the dimmer of compounds 1 to 3 in the high-symmetry form of D_2h has a high virtual frequency in b₃g symmetry. The results of TD-DFT studies also indicate that the distortions of the high-symmetry compounds 1 to 3 and their alteration into symmetric forms C_2h occur due to the PJTE (Ag+B₃g) Ä b₃g. In this regard also, the energy distance of composite reference electron levels (∆) is reduced from compound 1 to compound 3. Finally, the correlation between the structural parameters and the stability energy of PJTE in compounds 1 to 3 has been investigated.