Analysis of bonding patterns in the valence isoelectronic series O ₃, S₃, SO₂, and OS₂ in terms of oriented quasi-atomic molecular orbitals

A novel analysis of the chemical bonding pattern in the valence isoelectronic series of triatomic molecules O₃, S₃, SO₂, and OS₂ is reported. It is based on examining the bond order matrix elements between the oriented localized molecular orbitals (OLMOs) that are localized on the three individual atoms: left (L), center (C), and right (R). The analysis indicates that there is a (L-C) and (C-R) π-bonding interaction and a (L-R) π-antibonding interaction. It supports the earlier proposed "partial biradical" interpretation of these systems, which had recently been challenged. The degree of biradical character is shown to increase from SO₂ to S₃ to O₃ to OS₂.