title: Electronic Structure of Open-Shell Singlet Molecules: Diradical Character Viewpoint.
abstract: This chapter theoretically explains the electronic structures of open-shell singlet systems with a wide range of open-shell (diradical) characters. The definition of diradical character and its correlation to the excitation energies, transition properties, and dipole moment differences are described based on the valence configuration interaction scheme using a two-site model with two electrons in two active orbitals. The linear and nonlinear optical properties for various polycyclic aromatic hydrocarbons with open-shell character are also discussed as a function of diradical character.
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan. mnaka@cheng.es.osaka-u.ac.jp.|Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan. mnaka@cheng.es.osaka-u.ac.jp.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
mesh_terms: D004583:Electrons; D015394:Molecular Structure; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons
keywords: Diradical character; Excitation energy and property; Nonlinear optical property; Open-shell singlet; Valence configuration interaction