[(C 5 H 6 N 2 ) 2 H](Sb 4 F 13 ): 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) 2 (Sb 4 F 14 ) and (3AP) 2 (Sb 4 F 13 ), have been achieved. Interestingly, these two structures contain two new polyfluoroantimonite groups respectively, an isolated (Sb 4 F 14 ) 2- four-member polyhedral ring and an infinite [Sb 4 F 13 ] ∞ - helical chain. More importantly, the polar (3AP) 2 (Sb 4 F 13 ) 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 -2 . Theoretical calculations indicated that its strong SHG effect stems from the synergistic effect of the helical [Sb 4 F 13 ] ∞ - 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.