Synthesis and Characterization of the First Tin Fluoride Borate Sn3 [B3 O7 ]F with Second Harmonic Generation Response

The new non-centrosymmetric tin fluoride borate Sn-3[B3O7]F was synthesized hydrothermally, and was characterized by single-crystal and powder X-ray diffraction, vibrational spectroscopy, DFT calculations, second harmonic generation (SHG) measurements, thermogravimetry, and differential scanning calorimetry. Its SHG response is about 12 times that of quartz. The compound crystallizes in the noncentrosymmetric orthorhombic space group Pna2(1) with lattice parameters a= 922.4(2), b= 769.8(4), and c= 1221.9(6) pm (Z=4). Characteristic for the structure are isolated B3O7 moieties, consisting of two corner-sharing BO3 units and one BO4 tetrahedron. These occupy half of the octahedral voids of a slightly distorted hexagonal closest packing of Sn2+ atoms, with [SnF](+) units in the other half of the octahedral voids. Sn-3[B3O7]F is transparent over a wide spectral range with a UV cut-off edge at about 263 nm