Nonlinear OpticsMaterials Designed by IntramolecularBoron- and Nitrogen-Locking Strategies: Exploring Torsion Angle Descriptors

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 <i>R</i>² ranges from 0.84 to 1.00). Meanwhile, between θ₁, θ₂, and the excited energy (Δ<i>E</i>) of the crucial excited state there have also good correlations, namely, the <i>R</i>² 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.