Sb6 O7 (SO4 )2 : A Promising Ultraviolet Nonlinear Optical Material with an Enhanced Second-Harmonic-Generation Response Activated by SbIII Lone-Pair Stereoactivity.

The stereochemical activity of lone pairs (SCALP) in a cation favors the formation of acentric materials and can enhance the second-harmonic-generation (SHG) response and/or the birefringence. By introducing functional SbIII into sulfates, an anhydrous sulfate of Sb6 O7 (SO4 )2 (1) is explored. Sb3+ cations are in seesaw configurations and in-phase aligned in a 3D asymmetric dense structure. Compound 1 exhibits an enhanced phase-matching SHG response, a moderate birefringence, a wide transparency window, and considerable environmental stabilities, which result in it being a promising UV nonlinear optical (NLO) material. Theoretical studies reveal that the stereoactive lone pairs on Sb3+ cations make the predominant contribution to the SHG effect. This work will attract more interest from scientists for research into SCALP-cation-based NLO materials.