Planar tetracoordinate oxygen stabilized within triel-chalcogen dicationic frameworks

Planar tetracoordinate oxygen (ptO) challenges oxygen's intrinsic preference for two-coordinate bonding. We present a systematic investigation of dicationic triel-chalcogen clusters O©X₄E₄ ²⁺ (X = Al, Ga, In; E = S, Se, Te), identifying 9 D _4h ptO global minima. The oxygen atom is best described as a formally O^2- dianion electrostatically embedded within a charge-delocalized X₄E₄ tetracationic framework sustained by a robust X-E σ-scaffold, with negligible X-X interactions. Bonding analysis indicates predominantly electrostatic O-X interactions, whereas the X₄E₄ crown is stabilized by localized 2c-2e X-E σ-bonds and delocalized 3c-2e X-E-X π-bonds. Magnetic response calculations reveal localized diatropic vortices around the ptO center and the X-E-X regions, but no global ring current, consistent with the nonaromatic character. Born-Oppenheimer molecular dynamics simulations confirm dynamic stability at 500 K. π-Anion complexation with cyclooctatetraenide (COT^2-) demonstrates that retention of the planar geometry depends on intrinsic framework rigidity and is preserved in the aluminum derivatives. These results establish electrostatic embedding within a rigid X₄E₄ scaffold as an effective strategy for stabilizing ptO in main-group clusters.