Computational Probing of Schleyer's Hyperconjugative Aromaticity in a Novel Designed Anion Acceptor

Quantum chemical simulations were utilized to investigate the nature of the bonding of N^3-, P^3-, As^3-, O^2-, S^2-, Se^2-, F^-, Cl^-, and Br^- anions with the designed anion receptor cyclopenta-2,4-diene-1,1-diylbis(borane) abbreviated as CPDB and consecutive hyperconjugative aromaticity in its cyclopentadiene ring. Various analytical tools, including quantum theory of atoms in molecules (QTAIM), Electron Localization function (ELF), and reduced density gradient (RDG) were employed to explore the interaction between the selected anions and the CPDB structure. Moreover, the changes in the bond lengths (∆BL), harmonic oscillator model of aromaticity (HOMA), and localized orbital locator purely contributed by π-orbitals (LOL-π) analyses were performed to study the hyperconjugative aromaticity upon anion accepting. The findings indicate that the anions are connected to the CPDB structure through the electron deficiency of the B atoms and can induce the aromaticity via Schleyer's hyperconjugative aromaticity to the CPBD's ring. The nature of the interactions and hyperconjugative aromaticity effect of each anion is discussed in detail.