Manifestation of descent symmetry phenomena in tetrahedral structure of M42+ (M = P, As, Sb) analogues

Manifestation of descent symmetry phenomena induced by pseudo Jahn–Teller interactions is reported for the P4 dicationic tetrahedral structure and its As4 and Sb4 analogues. The symmetry descent phenomena in the dicationic tetrahedral structure for the series is caused by the pseudo Jahn–Teller effect (PJTE) where the unstable (high Td symmetry) configuration distorts to the equilibrium geometry with a lower, C2 symmetry. State averaging six low-lying electronic states via CASSCF(8,8)/cc-pVTZ–(PP) computations determined the adiabatic potential energy surfaces along the distorting normal coordinate. The (E(I) + A1 + E(II)) ⊗ e for the M42+ (M = P, As, Sb) series has been formulated accordingly. Subsequently, the coupling constants were estimated by fitting energies obtained from the PJTE equations. Moreover, to understand how removing or adding electrons affects the PJTE in the M42+ series, electronic configurations were analysed for M4(0,2+,4+) analogues in which the M4(0,4+) are stable in their tetrahedral structure.