[(CHN)H](SbF): a polyfluoroantimonite with a strong second harmonic generation effect.

It is of great difficulty to create a new antimonite with second-harmonic-generation (SHG) intensity larger than 6 times that of KDP. In this study, a polyfluoroantimonite strategy has been proposed to explore fluoroantimonites with large nonlinear optical (NLO) coefficients. Under the cooperation of chemical (highly asymmetric π-conjugated organic amine) and physical (viscous reaction medium ethylene glycol) methods, two novel polyfluoroantimonites, namely, (3PC)(SbF) and (3AP)(SbF), have been achieved. Interestingly, these two structures contain two new polyfluoroantimonite groups respectively, an isolated (SbF) four-member polyhedral ring and an infinite [SbF] helical chain. More importantly, the polar (3AP)(SbF) displays a strong SHG intensity of 8.1 × KDP, a large birefringence of 0.258@546 nm and a high laser-induced damage threshold (LIDT) value of 149.7 MW cm. Theoretical calculations indicated that its strong SHG effect stems from the synergistic effect of the helical [SbF] polyfluoroantimonite chain and π-conjugated 3AP cation, with a contribution ratio of 48.93% and 50.77% respectively. This work provides a new approach for the design and synthesis of high-performance fluoroantimonites.