1. Second Hyperpolarizability of Zethrenes.
- Author
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Nakano, Masayoshi, Kishi, Ryohei, Takebe, Akihito, Nate, Masahito, Takahashi, Hideaki, Kubo, Takashi, Kamada, Kenji, Ohta, Koji, Champagne, Benoît, and Botek, Edith
- Subjects
- *
POLARIZABILITY (Electricity) , *MOLECULAR orbitals , *ELECTRONS , *MOLECULES , *QUANTUM chemistry - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2007