CAl4X4 (X = Te, Po): Double Aromatic Molecular Stars Containing Planar Tetracoordinate Carbon Atoms

• Published in: Molecules (Basel, Switzerland) Vol. 28; no. 7; p. 3280
• Main Authors: Bai, Li-Xia, Guo, Jin-Chang
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 06.04.2023; MDPI
• Subjects: Aromaticity; Carbon; chemical bonding; Chemical bonds; Covalent bonds; Density functional theory; Design; double aromaticity; Energy; global minimum; Introduced species; Ligands; Molecular dynamics; planar tetracoordinate carbon; Potential energy; stability
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28073280

Planar tetracoordinate carbon (ptC) species are scarce and exotic. Introducing four peripheral Te/Po auxiliary atoms is an effective strategy to flatten the tetrahedral structure of CAl4 (Td, 1A1). Neutral CAl4X4 (X = Te, Po) clusters possess quadrangular star structures containing perfect ptC centers. Unbiased density functional theory (DFT) searches and high-level CCSD(T) calculations suggest that these ptC species are the global minima on the potential energy surfaces. Bonding analyses indicate that 40 valence-electron (VE) is ideal for the ptC CAl4X4 (X = Te, Po): one delocalized π and three σ bonds for the CAl4 core; four lone pairs (LPs) of four X atoms, eight localized Al–X σ bonds, and four delocalized Al–X–Al π bonds for the periphery. Thus, the ptC CAl4X4 (X = Te, Po) clusters possess the stable eight electron structures and 2π + 6σ double aromaticity. Born–Oppenheimer molecular dynamics (BOMD) simulations indicate that neutral ptC CAl4X4 (X = Te, Po) clusters are robust.