P-Block Heterobenzenes: Recurring Features in Structural, Vibrational, Electronic and Topological Properties

Abstract

• Systematic investigation of 40 p -block heterobenzenes in basic and acidic form • The trends of the geometrical features is quantitatively rationalised • The In-Plane Ring Normal Modes show peculiarities varying in groups and periods • A correlation between vibrational and topological characteristics is revealed Forty heterobenzenes involving the elements in groups 13 to 16, the valence isomers of benzene and pyridine, are systematically investigated through quantum mechanical calculations, using the DFT and the MP2 theory. The main goal is to rationalise the impact of heteroatoms on the molecular geometry, 7 in-plane ring related vibrational wavenumbers, force constants, frontier Molecular Orbitals (MOs), maps of Molecular Electrostatic Potential (MEP) as well as the topologic perspectives obtained from Atom in Molecule (AIM) analysis and Electron Localization Functions (ELF). Although the overall strength of C-X bond weakens along the periodic group, the covalent binding is identified even for the 6th period heteroatoms. A stronger π bond establishes between heavier heteroatoms and Carbons. Regardless of the heteroatoms, part or all of 7 RNMs belonging to pyridine vibrational features are identified for all the heterobenzenes and their wavenumbers and force constants exhibit periodic trends.