Symmetry breaking in the planar configurations of hydrazine, diphosphane and diarasane

Abstract: If the excited and ground electronic modes are mixed, the symmetry breaking in the high symmetrical configuration of a molecule is expected. It has been shown that high-symmetry forms of any molecule undergo structural distortions due to the pseudo-Jahn-Teller Effect (PJTE). The planar (D2h) and trans-bent (C2h) geometries of Hydrazine (1), Diphosphane (2), and Diarsane (3) have been optimized at the CCSD(T), LC-PBE, CAM-B3LYP and B3LYP levels with 6-311+G** the basis set on every atom. Furthermore, studies have explored the associations between the PJT stabilization energies, hardness, and structural factors and applied NBO interpretation to study the mixing between the H1–X2 bonding and LPX2 with X3-H5 anti-bonding configurations of 1–3 compounds. The energy gaps between the reference states )Δ (in the planar (D2h) structures decrease from 1 to 3 compounds ( 3.80,3.12 and 2.77 eV ). The plot of EPJT is linearly correlated with Δ [η (C2h)-η (D2h)] of compounds 1–3. The calculated Δ[η (C2h)-η (D2h)] parameter increases from 1 to 3 compounds. It was shown that the planar (D2h)is more unstable than the trans-bent (C2h) configuration, due to the strong lone pair–lone pair repulsion. PJT stabilization energy increases from compounds 1 to 3, which represent greater stability of 1 to 3 compounds.