Open-Shell Character and Nonlinear Optical Properties of Nanographenes

Authored by: Yoneda Kyohei , Nakano Masayoshi

Graphene Science Handbook

Print publication date:  April  2016
Online publication date:  April  2016

Print ISBN: 9781466591318
eBook ISBN: 9781466591325
Adobe ISBN:

10.1201/b19642-30

 Download Chapter

 

Abstract

Low-dimensional nanographenes such as graphene nanoflakes (GNFs) are known to display the unique spin states with nonbonding molecular orbitals localized on their zigzag edges, that is, “open-shell singlet” electronic state. The open-shell singlet nature presents a key concept for designing a new class of functional materials such as highly efficient nonlinear optical (NLO) and singlet fission materials. As an example, we have theoretically investigated the open-shell natures of GNFs with various architectures and sizes using the diradical characters, defined by quantum chemical calculations, and have revealed several structure—open-shell property relationships for the GNFs. It has been found that several zigzag-edged GNFs exhibit intermediate and large diradical characters, while GNFs having only armchair edges are closed-shell systems. Also, large GNFs are shown to display multiradical characters beyond the diradical as increasing the zigzag-edge lengths. We have further found unique structural dependences of multiradical characters in antidot hexagonal GNFs and linear GNFs composed of trigonal fused-ring units. These GNFs are expected to be possible candidates for highly efficient and tunable open-shell singlet NLO materials, which exhibit strong diradical character dependences of NLO properties and give large NLO properties as compared to conventional closed-shell NLO systems. The mechanism and rational design principle of various GNFs for highly efficient NLO materials are presented in this chapter.

 Cite
Search for more...
Back to top

Use of cookies on this website

We are using cookies to provide statistics that help us give you the best experience of our site. You can find out more in our Privacy Policy. By continuing to use the site you are agreeing to our use of cookies.