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Diradical Character Tuning for the Third‐Order Nonlinear Optical Properties of Quinoidal Oligothiophenes by Introducing Thiophene‐ S , S ‐dioxide Rings
Author(s) -
Kishi Ryohei,
Ochi Shoki,
Izumi Shioh,
Makino Akihiro,
Nagami Takanori,
Fujiyoshi Junya,
Matsushita Naoyuki,
Saito Michika,
Nakano Masayoshi
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201503705
Subject(s) - thiophene , diradical , character (mathematics) , order (exchange) , nonlinear system , chemistry , materials science , physics , mathematics , organic chemistry , quantum mechanics , geometry , singlet state , excited state , finance , economics
To create a design guideline for efficient third‐order nonlinear optical (NLO) molecules, the chain‐length ( n ) dependences of the diradical character y and the longitudinal second hyperpolarizability γ of quinoidal oligothiophenes (QTs), from monomers to octamers, involving thiophene‐ S , S ‐dioxide rings are investigated by using the density functional theory method. It turns out that the diradical character of the modified QTs is reduced as compared to those of the pristine QTs. By introducing an appropriate number of oxidized rings into the QT framework, intermediate y values can be achieved even in the systems with large values of n , in which the pristine QTs are predicted to have pure diradical character. Such intermediate diradical oligomers are shown to exhibit enhanced γ values as compared to the pristine QTs with the same value for n . From the calculation results, the introduction of the optimal number of thiophene‐S,S‐dioxide rings is predicted to be an efficient chemical modification for optimizing the third‐order NLO properties of open‐shell QTs through tuning the diradical characters.