title: Applications of natural orbitals for chemical valence in a description of bonding in conjugated molecules.
abstract: Natural orbitals for chemical valence (NOCV) were used to describe bonding in conjugated pi-electron molecules. The 'single' C-C bond in trans-1,3-butadiene, 1,3-butadiene-1,1,4,4-tetra-carboxilic acid, 1,3,5,7-octatetraene, and 11-cis-retinal was characterized. In the NOCV framework, the formation of the sigma-bond appears as the sum of two complementary charge transfer processes from each vinyl fragment to the bond region, and partially to the other fragment. The formation of the pi-component of the bond is described by two pairs of NOCV representing the transfer of charge density from the neighboring 'double' C-C bonds. The NOCV eigenvalues and the related fragment-fragment bond multiplicities were used as quantitative measures of the sigma- and pi- contributions. The sigma-component of the 'single' C-C bonds appears to be practically constant in the systems analyzed, whereas the pi-contributions increase from butadiene (ca. 7.5%) to retinal (ca. 14%).
authors.affiliation: Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, R. Ingardena 3, 30-060, Kracow, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Mitoraj
authors.forename: Artur
authors.initials: A
authors.lastname: Michalak
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002070:Butadienes / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D008432:Mathematical Computing; D008956:Models, Chemical; D012172:Retinaldehyde / Q000737:chemistry*
chemical_list: D000475:Alkenes; D002070:Butadienes; D002264:Carboxylic Acids; C031763:1,3-butadiene; D012172:Retinaldehyde