Synthesis and Characterization of ASnOAsO4(A = K and Rb)

Crystals of two alkali-metal tin(IV) arsenates, KSnOAsO₄ and RbSnOAsO₄, were grown from a flux and structurally characterized by single-crystal X-ray diffraction. Crystal data: RSnOAsO₄, orthorhombic, Pna2₁ (No. 33), a = 13.406(3) Å, b = 6.678(1) Å, c = 10.921(2) Å, Z = 8, R = 0.037 for 1173 independent reflections with I > 2.5ó(l); RbSnOAsO₄, as above except a = 13.567(3) Å, b = 6.791( 1) Å, c = 10.891(2) Å, R = 0.035 for 1958 independent reflections. The two compounds are isostructural with the nonlinear optical material KTiOPO₄. The oxygen frameworks of both tin compounds approximate closely to a centrosymmetric arrangement, as indicated from the analysis of atomic coordinates. Second harmonics were generated in powdered RbSnOAsO₄ to confirm the absence of a center of symmetry in the structure.