The tin sulfates Sn(SO₄)₂ and Sn2(SO4)3: crystal structures, optical and thermal properties

We report the crystal structures of two tin(IV) sulfate polymorphs Sn(SO4)2-I (P2₁/c (no. 14), a = 504.34(3), b = 1065.43(6), c = 1065.47(6) pm, β = 91.991(2)°, 4617 independent reflections, 104 refined parameters, wR₂ = 0.096) and Sn(SO4)2-II (P2₁/n (no. 14), a = 753.90(3), b = 802.39(3), c = 914.47(3) pm, β = 92.496(2)°, 3970 independent reflections, 101 refined parameters, wR₂ = 0.033). Moreover, the first heterovalent tin sulfate Sn2(SO4)3 is reported which adopts space group P1̄ (no. 2) (a = 483.78(9), b = 809.9(2), c = 1210.7(2) pm, α = 89.007(7)°, β = 86.381(7)°, γ = 73.344(7)°, 1602 independent reflections, 152 refined parameters, wR₂ = 0.059). Finally, SnSO4 - the only tin sulfate with known crystal structure - was revised and information complemented. The optical and thermal properties of all tin sulfates are investigated by FTIR, UV-vis, luminescence and ¹¹⁹Sn Mössbauer spectroscopy as well as thermogravimetry and compared.