An intramolecular-locked strategy for designing nonlinear optical materials with remarkable first hyperpolarizability.

To meet the expanding demands of high performance nonlinear optical (NLO) materials, an unprecedented intramolecular-locked strategy is proposed to design NLO materials with remarkable static first hyperpolarizability (β0). This strategy means that importing a large steric hindrance group diphenylmethane (DPM) decreases the torsion angles (θ) between the donor {triphenylamine (TPA)} and acceptor {9-H-thioxanthen-9-one-10,10-dioxide (TXO)} units, as well as between the donor (TPA) and π-bridge (benzene) fragments. The decrease of θ can accelerate the intramolecular charge transfer and enhance the contributions of the TPA, TXO and quinoxaline-6,7-dicarbo-nitrile (QCN) fragments to the axial component of the β0 value, and then the β0 values of TPA-TXO (β0 = 10 762 au) and TPA-QCN (β0 = 22 495 au) are increased by 14.9% and 34.4%, respectively. Overall, the intramolecular-locked strategy is very effective for designing high performance NLO materials.