2016/08/26 by Igor V. Alabugin · 1 citation
Chemistry · Engineering · #Synthesis and Properties of Aromatic Compounds #Molecular Junctions and Nanostructures #Organic Electronics and Photovoltaics
paper · doi:10.1002/9781118906378.ch8
openalex publication_date 2016/08/26 · openalex created_date 2022/05/12 · openalex updated_date 2026/04/30
Conjugation through continuously connected extended π-arrays is well-known to provide long-range electronic communication. A number of extended hyperconjugation patterns have been shown to be effective as well. Long-range delocalization can follow a variety of patterns that combine conjugation and hyperconjugation and are mediated by through-bond (TB) and through-space (TS) interactions. Homoconjugation and homohyperconjugation are observed when a saturated center intervenes between donor and acceptor orbitals. Homoaromaticity is well-established in charged systems and can involve either a planar or a three-dimensional array of atoms. Cross-hyperconjugation results from the delocalization of π-electrons into the pseudo-π* orbitals, acting effectively as a cross-conjugated system. Through-bond interactions can evolve into concerted fragmentation. Symmetry effects in cyclic systems can lead to enhancing or weakening of hyperconjugation and conjugation, leading to σ-aromatic or antiaromatic systems. Independent arrays of delocalizing interactions can exist in a molecule. For example, formation of a σ-aromatic system in the presence of an orthogonal aromatic π-system leads to double aromaticity.