Issue 5, 2017

A theoretical study on quasi-one-dimensional open-shell singlet ladder oligomers: multi-radical nature, aromaticity and second hyperpolarizability

Abstract

Quasi-one-dimensional open-shell ladder oligomers composed of fully conjugated five- and six-membered rings are investigated to describe their open-shell singlet character and their third-order nonlinear optical (NLO) responses using density functional theory calculations. The nature of the repeating structures is shown to modify the multi-radical nature described by multiple diradical characters, the bond-length alternation, and the local aromaticity. The calculation of the third-order NLO properties (γ, the second hyperpolarizability) reveals that the open-shell ladder oligomers with small multiple diradical characters exhibit the largest γ values. At the infinite chain length limit, the static γ value per fused-ring is estimated to reach about 3.6 times that of polyacene, and about half that of all-trans-polyacetylene. The present study gives the first detailed clarification of the multi-radical character and the local aromaticity in real multi-radical ladder oligomers, and the first demonstration that these oligomers are efficient NLO candidates with both large γ and high rigidity.

Graphical abstract: A theoretical study on quasi-one-dimensional open-shell singlet ladder oligomers: multi-radical nature, aromaticity and second hyperpolarizability

Supplementary files

Article information

Article type
Research Article
Submitted
08 Feb 2017
Accepted
03 Mac 2017
First published
06 Mac 2017

Org. Chem. Front., 2017,4, 779-789

A theoretical study on quasi-one-dimensional open-shell singlet ladder oligomers: multi-radical nature, aromaticity and second hyperpolarizability

K. Fukuda, J. Fujiyoshi, H. Matsui, T. Nagami, S. Takamuku, Y. Kitagawa, B. Champagne and M. Nakano, Org. Chem. Front., 2017, 4, 779 DOI: 10.1039/C7QO00108H

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