Synthesis, crystal structures of ASb(SO4)2 (A = K, Cs)

The reactions of A 2 SO 4 ( A  = K, Cs) and Sb 2 O 3 with H 2 SO 4 (98%) yielded single crystals of A Sb(SO 4 ) 2 ( A  = K, Cs). The crystal structures were investigated by single crystal X-ray diffraction. KSb(SO 4 ) 2 crystallizes in the monoclinic space group P 2 1 / c (No. 14) with lattice parameters a  = 10.6745(18), b  = 7.1579(12), c  = 8.7597(15) Å, β = 91.466(3) ° , V  = 669.1(2) Å 3 , Z  = 4. CsSb(SO 4 ) 2 crystallizes in the orthorhombic space group P 2 1 2 1 2 1 (No.19) with lattice parameters of a  = 5.2429(8), b  = 9.5942(16), c  = 14.850(2) Å, V  = 746.98(20) Å 3 , Z  = 4. Both compounds show the Sb 3+ cations in same seesaw-type coordination of oxygen atoms from different SO 4 2 − ${{\text{SO}}_4}^{2-}$ anions, but exhibit complex two-dimensionally and one-dimensionally linked anionic structures. The alkali cations are located between the layers or chains. The compounds were characterized with FT-IR spectra and solid state UV–vis–NIR diffuse reflectance spectroscopy . The band gaps were estimated at 4.64 eV for KSb(SO 4 ) 2 and 4.68 eV for CsSb(SO 4 ) 2 .