RbEu[AsS4], Rb4Eu[AsS4]2 and CsEu[AsS4]: Three europium(II) thioarsenates(V) with the heavy alkali metals

Three novel europium(II) thioarsenates(V) ( 1 ), ( 2 ), and ( 3 ) were synthesized by using the molten polysulfide-flux method. and crystallize isotypically in the orthorhombic space group Pnma with a = 1729 . 53 ( 9 ) pm , b = 679 . 18 ( 4 ) pm , c = 670 . 46 ( 4 ) pm for ( 1 ) and a = 1796 . 48 ( 9 ) pm , b = 686 . 54 ( 4 ) pm , c = 663 . 35 ( 4 ) pm for ( 3 ) with Z = 4 . An attempt to obtain single-phase by changing the molar ratio of the reactants and optimizing the synthesis temperature led to as main product and as a second phase, which crystallizes orthorhombically in the space group Ibam with a = 913 . 46 ( 5 ) pm , b = 1873 . 08 ( 11 ) pm , c = 1010 . 23 ( 6 ) pm for Z = 4 . All crystal structures contain isolated anions with sulfur corners and edges building -centered polyhedra, whose condensation leads to 2 ∞ { [ Eu (S1) 1 / 1 t (S2) 3 / 3 e (S3) 4 / 2 e ] 6 − } layers separated by and cations for ( 1 ) and ( 3 ) or -linked 1 ∞ { [ Eu (S2) 4 / 2 e (S3) 4 / 1 t ] 6 − } chains in the case of ( 2 ). Single-crystal Raman spectroscopy was performed for all compounds showing the typical vibrational modes of discrete tetrahedral groups. • Synthesis and structure analysis of three new compounds comprising tetrahedra. • and crystallize isotypically with a 2D layer structure. • The structure of is characterized by a 1D chain arrangement.