Symmetry breaking in the linear configurations of SX2 (X=F, Cl, Br, I): Pseudo-Jahn- Teller effect parameters, hardness and electronegativity

The instability of the curved structure in SX2(X=F ,Cl ,Br ,I) molecules due to the pseudo Jahn-Teller effect(PJTE) was investigated as an original PJTE study, which were bent in the ground state and linear in their first excited state.The effective parameters in vibronic coupling between reference states [HOMO(Πu)→LUMO(Ʃg)] have been investigated in linear structures(D∞h).Calculations at the B3LYP/Def2-TZVPP level of theory produced the structural parameters, corrected electronic energies, electro negativity and hardness.The natural bond orbital (NBO)interpretation is associated with [Lp(3)X →σ*(1)S-X] to obtain stabilization energy (E(2)),vibronic coupling constant(Fij) and energy gaps between reference states(Δ).The interactions and effectiveness of these parameters with the structural parameters of the desired compounds were the focus of the study. In all above mentioned molecules stability were increased ith the reduction in the symmetry level. The hardness difference parameter Δ[η (C2V) -η (D∞h)] decreases from F to I (44.05,37.13, 30.19, 25.14 Kcal/mol).These changes could explain the trend, which were observed for the D∞h→ C2V conversion process.