A novel acid-controlled second-order nonlinear optical switch based on dimethyldihydropyrene/cyclophanediene photoswitch

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2022-09, Vol.1 (34), p.12338-12349
• Main Authors: Yao, Yao, Xu, Hong-Liang, Su, Zhong-Min
• Format: Article
• Language: English
• Subjects: Aniline; Conjugation; Electronic structure; Nonlinear control; Nonlinear optics; Optical memory (data storage); Optical switching; Organic materials; Protonation; Quinoxalines; Switches
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc02521c

Nonlinear optical (NLO) switches, especially multi-state NLO switches, have attracted much attention because of their applications in optical memory with multiple storage and nondestructive capacity. However, it is still a challenge to design new second-order NLO switch molecules with high first hyperpolarizability ( β ) contrasts. In this study, we theoretically investigated the second-order NLO property and second-order NLO switch effect of dimethyldihydropyrene photoswitch derivatives with a push-pull electronic structure during protonation. Remarkably, the quinoxaline acceptor-based systems have a larger β ratio contrast, demonstrating a simple "ON"-"OFF" NLO switch. Interestingly, the system with a pyridine acceptor and aniline donor showed a multi-state "ON"-"OFF"-"ON" NLO switch under light-triggered and pH-triggered transformations. Furthermore, the DFT and TDDFT calculations provided meaningful insights into their structure-property relationship. Specifically, a large second-order NLO response was displayed in the protonation of the acceptor, resulting from the production of a stronger electron push-pull structure, larger π-conjugation, and more obvious CT transition. However, a weak NLO response was observed upon the protonation of the donor because of inhibiting electron-donating ability, reducing the degree of π-conjugation and producing a predominant LE transition. We hope that the present work will provide a theoretical guide for the design of multifunctional organic materials based on the DHP core. The structure of the DHP-CPD core was modified chemically by different acceptor and donor groups, showing interesting NLO switch characteristics upon protonation.