Authors: Nakano, Masayoshi¹; Kishi, Ryohei¹; Takebe, Akihito¹; Nate, Masahito¹; Takahashi, Hideaki¹; Kubo, Takashi²; Kamada, Kenji³; Ohta, Koji³; Champagne, Benoît⁴; Botek, Edith⁴

Source: Computing Letters, Volume 3, Numbers 2-4, 2007 , pp. 333-338(6)

Publisher: VSP, an imprint of Brill

Abstract:

We report a study on the static second hyperpolarizabilities (γ) of zethrenes using the UBHandHLYP hybrid density functional theory method. Though zethrenes were originally considered as closed-shell systems, the values of their diradical characters, calculated from the occupation numbers of spin-unrestricted Hartree-Fock natural orbitals (UNOs), demonstrate an open-shell diradical nature, which increases with the size of the middle ring region because of the recovery of the aromaticity in that region. As references, we examine also the γ values of tetrabenzopolyacenes, which are regarded as the corresponding closed-shell systems due to their negligible diradical characters. It is found that the longitudinal γ values for zethrenes are much larger than those of the corresponding reference closed-shell systems, whereas their ratio, γ(zethrene)/γ(reference), is reduced when increasing the length of middle ring regions, i.e., when increasing the diradical character.

Keywords: HYPERPOLARIZABILITY; DIRADICAL; ZETHRENE; POLYACENE; OPEN-SHELL

Document Type: Research article

Affiliations: 1: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan 2: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan 3: Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577, Japan 4: Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix (FUNDP), rue de Bruxelles, 61, B-5000 Namur, Belgium

Publication date: 2007-11-01

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