A computational study of planar tetracoordinated carbon species CAl4X5 (X = Te, Po) with One X–X Bond

Abstract

Planar tetracoordinate carbon (ptC) species have attracted widespread attention and research interest, due to their unique electronic structures and exotic properties. Here, we report the ptC CAl₄X₅ (X = Te, Po) species with one novel X–X bond. CAl₄X₅ (X = Te, Po) have one trapezoid-like CAl₄ core, surrounded by one X₂ and three X bridges. Density functional theory (DFT) isomeric searches and high-level CCSD(T) calculations reveal that the ptC CAl₄X₅ (X = Te, Po) species are the global minima (GMs) on their potential energy surfaces. Born–Oppenheimer molecular dynamics (BOMD) simulations indicate that the ptC structures of CAl₄X₅ (X = Te, Po) are robust. Bonding analyses reveal that one delocalized π and three σ bonds are responsible for the CAl₄ core, which seems to endow these ptC systems 2π+6σ aromaticity. However, the non-squaring of the CAl₄ structure and the ionization of the C–Al bonds significantly weaken the aromaticity of CAl₄X₅ (X = Te, Po). Interestingly, one localized X–X σ bond makes them the unique ptC systems. The ptC CAl₄X₅ (X = Te, Po) species containing one Te–Te/Po–Po bond may be characterized experimentally to further enrich the ptC chemistry.