Open Access

Vivien Wessels, Matthias Hämmer, Narayan Simrit Kaur, Lkhamsuren Bayarjargal, Henning A. Höppe

• The new sulfatotungstate Cs6[(WO2)2O(SO4)4] exhibits a hitherto unknown anion with an unusual W–O–W angle of 180° and edge-sharing WO6 and SO4 polyhedra. It crystallises in the monoclinic space group P21/c (no. 14) with Z = 2, determined by single-crystal X-ray diffraction. K8[(MoO2)2(SO4)6] and K7.9Sr0.1[(WO2)2(SO4)6] crystallise isotypic to each other in the monoclinic space group P21/n (no. 14) with Z = 2. Na4[MoO2(SO4)3] crystallises in the orthorhombic non-centrosymmetric space group P212121 (no. 19) with Z = 4, confirmed by second harmonic generation measurements. UV–vis measurements show a bright absorption below 400 nm for all compounds due to the ligand-to-metal charge transfer (LMCT) in tungstate and molybdate moieties. In the fluorescence spectra Cs6[(WO2)2O(SO4)4], K8[(MoO2)2(SO4)6] and K7.9Sr0.1[(WO2)2(SO4)6] show an emission of the LMCT. Further, all compounds were characterised by FT-IR spectroscopy and thermogravimetric analysis. Latter reveals remarkably high thermalThe new sulfatotungstate Cs6[(WO2)2O(SO4)4] exhibits a hitherto unknown anion with an unusual W–O–W angle of 180° and edge-sharing WO6 and SO4 polyhedra. It crystallises in the monoclinic space group P21/c (no. 14) with Z = 2, determined by single-crystal X-ray diffraction. K8[(MoO2)2(SO4)6] and K7.9Sr0.1[(WO2)2(SO4)6] crystallise isotypic to each other in the monoclinic space group P21/n (no. 14) with Z = 2. Na4[MoO2(SO4)3] crystallises in the orthorhombic non-centrosymmetric space group P212121 (no. 19) with Z = 4, confirmed by second harmonic generation measurements. UV–vis measurements show a bright absorption below 400 nm for all compounds due to the ligand-to-metal charge transfer (LMCT) in tungstate and molybdate moieties. In the fluorescence spectra Cs6[(WO2)2O(SO4)4], K8[(MoO2)2(SO4)6] and K7.9Sr0.1[(WO2)2(SO4)6] show an emission of the LMCT. Further, all compounds were characterised by FT-IR spectroscopy and thermogravimetric analysis. Latter reveals remarkably high thermal stabilities, especially for Cs6[(WO2)2O(SO4)4].…