title: Organic nonlinear optical materials: the mechanism of intermolecular covalent bonding interactions of Kekulé hydrocarbons with significant singlet biradical character.
abstract: The ground- and excited-state properties of benzene-linked bisphenalenyl (B-LBP), naphthaline-linked bisphenalenyl (N-LBP), and anthracene-linked bisphenalenyl (A-LBP) Kekulé molecules and their respective one-dimensional (1D) stacks are investigated using time-dependent density functional theory (TD-DFT) and a range of extensive multidimensional visualization techniques. The results reveal a covalent π-π bonding interaction between overlapping phenalenyl radicals whose bond length is shorter than the van der Waals distance between carbon atoms. Increasing the linker length and/or number of molecules involved in the 1D stack decreases the HOMO-LUMO energy gap and increases the wavelength of the systems. The charge-transfer mechanism and electron coherence both differ with changes in the linker length and/or number of molecules involved in the 1D stack.
authors.affiliation: Department of Physics, Liaoning University, Shenyang 110036 (China).
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Jiarui
authors.initials: J
authors.lastname: Xia
authors.forename: Peng
authors.initials: P
authors.lastname: Song
authors.forename: Yong
authors.initials: Y
authors.lastname: Ding
authors.forename: Yanling
authors.initials: Y
authors.lastname: Cui
authors.forename: Xuemei
authors.initials: X
authors.lastname: Liu
authors.forename: Yumei
authors.initials: Y
authors.lastname: Dai
authors.forename: Fengcai
authors.initials: F
authors.lastname: Ma
keywords: Charge transfer; covalent bonding interactions; electron-hole coherence; organic optical materials; singlet biradical character