The search for a maximum of the D-π-A paradigm for second order nonlinear optical molecular materials

Cui-Cui Yang; Xiao Su; Qi-Zheng Zheng; Jiu Chen; Wei Quan Tian; Wei-Qi Li; Ling Yang

doi:10.1039/d3cp03756h

The search for a maximum of the D-π-A paradigm for second order nonlinear optical molecular materials

Phys Chem Chem Phys. 2023 Nov 22;25(45):31481-31492. doi: 10.1039/d3cp03756h.

Authors

Cui-Cui Yang^{1

2}, Xiao Su², Qi-Zheng Zheng², Jiu Chen², Wei Quan Tian², Wei-Qi Li^{3

4

5}, Ling Yang⁶

Affiliations

¹ College of Science, Chongqing University of Technology, Chongqing 400054, China.
² Chongqing Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China. tianwq@cqu.edu.cn.
³ Department of Physics, Harbin Institute of Technology, Harbin 150001, China. tccliweiqi@hit.edu.cn.
⁴ Technology Innovation Center of Materials and Devices at Extreme Environment, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China.
⁵ Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, P. R. China.
⁶ Wenzhou Institute, University of Chinese Academy of Sciences, 1 Jinlian Street, Wenzhou 325001, China. lyang@ucas.ac.cn.

PMID: 37962477
DOI: 10.1039/d3cp03756h

Abstract

Push-pull π-conjugated molecules are one of the paradigms of second order nonlinear optical (NLO) materials and have been extensively explored. However, high-performance second order NLO materials with an optimum electron donor (D), π-bridge (π) and acceptor (A) under this paradigm are still the most sought-after. In the present work, D-π-A molecules with optimal D, π and A combination for strong second order NLO properties are proposed based on molecular orbital theories. The optimal D-π-A push-pull molecule achieves an unprecedentedly strong NLO response under the D-π-A paradigm, i.e., the static first hyperpolarizability reaches -453.92 × 10^-30 esu per heavy atom using azulene as part of the π-bridge and acceptor to synergistically reinforce the strength of the acceptor. The protocols of D-π-A NLO molecule design through frontier molecular orbital matching of D, π and A with optimal combination of electron donating and accepting strengths shed light on future molecular NLO materials exploration. The simulated two-dimensional second order spectra provide useful information (e.g., sum frequency generation) on the applications of those D-π-A push-pull molecules in nonlinear optics.