RESUMO
Aside from amorphous phases, only a single crystalline tin borate had been synthesised so far under high pressure. In this work, we present the very first crystalline ternary tin borate Sn3B4O9 synthesised under ambient pressure by decomposition of Sn3[B3O7]F above 500 °C. The crystal structure of Sn3B4O9 (P21/c, Z = 4, a = 768.07(3) pm, b = 1206.78(4) pm, c = 924.96(3) pm, ß = 101.847(1)°, 10 550 data, 147 parameters, R1 = 0.028) determined by single-crystal X-ray diffraction comprises open layered borate polyanions with Sn(ii) ions in-between showing the presence of a stereochemically active lone pair. Sn3B4O9 was further characterized by DFT calculations and vibrational spectroscopy. Its optical band gap was calculated to approx. 3.5(1) eV. Tin borate was gained by thermal decomposition of Sn[B2O3F2] via a further new tin borate fluoride Sn2[B7O12]F (C2/c, Z = 8, a = 1037.99(2) pm, b = 859.78(2) pm, c = 2370.71(8) pm, ß = 93.5650(10)°, 2674 data, 199 parameters, R1 = 0.045).
RESUMO
The new non-centrosymmetric tin fluoride borate Sn3 [B3 O7 ]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 non-centrosymmetric orthorhombic space group Pna21 with lattice parameters a=922.4(2), b=769.8(4), and c=1221.9(6)â pm (Z=4). Characteristic for the structure are isolated B3 O7 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. Sn3 [B3 O7 ]F is transparent over a wide spectral range with a UV cut-off edge at about 263â nm.
RESUMO
The very first alkaline-earth fluorooxoborate Ba[B4 O6 F2 ] was synthesised by solid state methods starting from Ba(BF4 )2 , ß-BaB2 O4 , and B2 O3 . The crystal structure derived from single-crystal X-ray diffraction (P21 /n, a=6.6384(2)â Å, b=7.6733(3)â Å, c=11.3385(4)â Å, ß=91.281(2)°, Z=4, Rint =0.0269, R1 =0.018, wR2 =0.034) comprises layers of BO3 F tetrahedra condensed through triangular BO3 units according to the descriptor 2Δ2â¡:<Δ2â¡>Δ. The extraordinary thirteen-fold coordination of barium by oxygen and fluorine leads to interesting optical properties of a sample doped with divalent europium, where a 4fâ4f emission was recorded around 359â nm together with a broad emission band of a 5dâ4f emission peaking at 366â nm. The compound is further characterised by IR-, Raman-, and solid-state NMR-spectroscopic methods. Moreover, DFT calculations as well as TGA and DSC measurements were performed.