During systematic research on the mineral-related synthetic arsenates, with particular focus on their structural and spectroscopic classification, three new Sr-containing arsenates Sr2Mg(AsO4)2 · 2H2O (1), Sr2Zn4(AsO4)4·H2O (2) and Sr2Cu7(AsO4)6 (3) have been synthesized under low-temperature hydrothermal conditions in the system SrO−MO−As2O5−H2O (M2+ = Mg, Zn, Cu). Their crystal structures were determined using room-temperature single-crystal X-ray diffraction data and refined to the following R-values: 1R1 = 0.025; 2R1 = 0.030; 3R1 = 0.035. Compounds 1 and 2 are structural analogues of two different arsenate minerals: 1 is the Sr analogue of talmessite, Ca2Mg(AsO4)2 · 2H2O, and 2 is the Sr analogue of prosperite, Ca2Zn4(AsO4)4 · H2O. Compound 1 is the first synthetic compound incorporating kröhnkite-type chains where a divalent cation occupies the interstitial A position (A2M(XO4)2 · 2H2O, A = Ca2+, Na+; M = Mg2+, Fe2+, Mn2+, Co2+, Ni2+, Cu2+; X = P5+, As5+, S6+). Compound 3 represents the second structurally characterized phase in the ternary SrO−CuO−As2O5 system besides SrCuAs2O7. The investigation showed that it is isotypic with Pb2Cu7(AsO4)6 and Ba2Cu7(AsO4)6. The CuOx (x = 4, 5, 6) polyhedra in 3 and in Pb and Ba analogues show a wide range of coordination geometries. This article focuses on the similarities and differences in their crystal structures and topology.

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