Structural and Electronic Properties of Star-like Compounds with a Central Planar Carbon Atom and <i>D</i> _<i>nh</i> ( <i>n</i> = 3–5) Symmetries

A new database predicted with theoretical chemistry of organometallic star-like compounds with a central planar carbon atom, named Star-Database, is presented. Planar star-like structures with D3h, D4h, and D5h symmetries are considered, where the central carbon atom is three-, tetra-, or penta-coordinated in a single plane. Combinations of atoms ranging from hydrogen to bismuth (excluding noble gases, lanthanides, and actinides) were considered along with charges of +1, 0, and −1. The systems have been generated through a systematic geometric and energetic screening, employing a multistep optimization and filtering protocol based on density functional theory (DFT), DFT-D3, and Møller–Plesset (MP2 and MP4) methods. All the molecules in the Star-Database satisfy three geometrical criteria: (a) planarity, (b) star-like geometry (the peripheral atoms arranged symmetrically around the central carbon resembling a star), and (c) coordination. There are 40-D3h, 19-D4h, and 10-D5h star-like planar molecules in the Star-Database. The elemental abundance with symmetry is analyzed. The most abundant elements in the first coordination sphere are metals (Pd, Pt), and in the second coordination are nonmetals (Se, I) > Te > H > F, Cl. The Star-Database provides atomic coordinates, HOMO–LUMO energy gaps and orbitals, and XY-NICS maps of aromaticity. Only 19 star-molecules are potentially aromatic.