An Unprecedented Antimony(III) Borate with Strong Linear and Nonlinear Optical Responses

Antimony(III) borates with a stereochemical active lone pair remained unknown, although the first antimony borate was reported more than twenty years ago. Now, the first antimony(III) borate in a closed system is successfully synthesized, namely SbB3O6. Remarkably, SbB3O6 not only exhibits an exceptional linear optical response, that is, birefringence of Δn=0.290 at the wavelength of 546 nm, which is the largest among borates, but also has a strong nonlinear optical response of 3.5 times larger than the benchmark KH2PO4, exceeding those of most borates. Theoretical calculations reveal that the coexistence of strong linear and nonlinear optical responses in SbB3O6 should be attributable to the synergistic effect of π‐conjugated B−O anionic groups and Sb3+ with stereochemically active lone pair. This work provides a new class of optical bi‐functional materials with potential prospects in integrated optical devices. An antimony(III) borate, SbB3O6, has been synthesized. It exhibits not only a linear optical response (Δn=0.290 @ 546 nm), which is the largest among borates, but also a strong nonlinear optical response (SHG=3.5×KH2PO4) that exceeds most borates.