Nonlinear Optics Materials Designed by Intramolecular Boron- and Nitrogen-Locking Strategies: Exploring Torsion Angle Descriptors.

Abstract

Gaining mechanistic insights into the structure-performance relationship connecting the donor and acceptor is essential to the rational design of high performance nonlinear optics (NLO) materials. Here, intramolecular boron/nitrogen (B/N)-locking strategies in combination with various electron-withdrawing groups, R (R = TXO, DPzS, TTR, DPyS, DTC, DSCZ, DMPS and TXO2), are proposed to address this issue. With the decreasing of torsion angles (θ₁ and θ₂) between donor (TPA) and acceptor (Py-Ph) units, the first hyperpolarizability (β) values are increased 45-65% and 4-27% by intramolecular B/N-locking strategies, respectively. Intriguingly, we also found some good linear correlations between θ₁, θ₂, and lgβ (where the determination coefficient R² ranges from 0.84 to 1.00). Meanwhile, between θ₁, θ₂, and the excited energy (ΔE) of the crucial excited state there have also good correlations, namely, the R² ranges from 0.80 to 1.00. As a result, given the fact of finding results, one can draw some meaningful insights, namely, intramolecular B/N-locking strategies hold good application perspective for enhancing β, and θ₁ and θ₂ can serve as effective descriptors in designing high-performance NLO materials based on the D-A architecture system.