Nonlinear optical properties in open-shell molecular systems

Masayoshi Nakano, Benoît Champagne

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Abstract

For more than 30 years, nonlinear optical (NLO) properties of molecular systems have been actively studied both theoretically and experimentally due to their potential applications in photonics and optoelectronics. Most of the NLO molecular systems are closed-shell species, while recently open-shell molecular species have been theoretically proposed as a new class of NLO systems, which exhibit larger NLO properties than the traditional closed-shell NLO systems. In particular, the third-order NLO property, the second hyperpolarizability γ, was found to be strongly correlated to the diradical character y, which is a quantum-chemically defined index of effective bond weakness or of electron correlation: the γ values are enhanced in the intermediate y region as compared to the closed-shell (y = 0) and pure open-shell (y = 1) domains. This principle has been exemplified by accurate quantum-chemical calculations for polycyclic hydrocarbons including graphene nanoflakes, multinuclear transition-metal complexes, main group compounds, and so on. Subsequently, some of these predictions have been substantiated by experiments, including two-photon absorption. The fundamental mechanism of the y–γ correlation has been explained by using a simple two-site model and the valence configuration interaction method. On the basis of this y–γ principle, several molecular design guidelines for controlling γ have been proposed. They consist in tuning the diradical characters through chemical modifications of realistic open-shell singlet molecules. These results open a new path toward understanding the structure—NLO property relationships and toward realizing a new class of highly efficient NLO materials. WIREs Comput Mol Sci 2016, 6:198–210. doi: 10.1002/wcms.1242.

Original languageEnglish
Pages (from-to)198-210
Number of pages13
JournalWiley Interdisciplinary Reviews: Computational Molecular Science
Volume6
Issue number2
DOIs
Publication statusPublished - 1 Mar 2016

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Optical Devices
Optical Properties
Shell
Optical properties
optical properties
Optical systems
Cyclic Hydrocarbons
Optics and Photonics
Electron correlations
Optical materials
Graphite
Coordination Complexes
Chemical modification
optical materials
Metal complexes
Photons
Closed
Optoelectronic devices
Optical System
Photonics

Keywords

  • Nonlinear optical properties
  • open shell molecular system

Cite this

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Nonlinear optical properties in open-shell molecular systems. / Nakano, Masayoshi; Champagne, Benoît.

In: Wiley Interdisciplinary Reviews: Computational Molecular Science, Vol. 6, No. 2, 01.03.2016, p. 198-210.

Research output: Contribution to journalArticle

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