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 2 2017
Accepted
03 3 2017
First published
06 3 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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