Bi2O(XO4)(IO3)2 (X = S, Se, Cr): Three-dimensional frameworks containing [Bi4O2]8+ clusters

Three new bismuth-based compounds, Bi 2 O(XO 4 )(IO 3 ) 2 (X = S, Se, Cr) have been synthesized by hydrothermal method and characterized by single-crystal X-ray diffraction. Title compounds crystallize in the monoclinic space group P 2 1 /n (No.14) with lattice parameters: a  = 7.2391(5), b  = 17.9074(12), c  = 7.7964(5) Å, β  = 109.6521(15) °, Z = 4 for Bi 2 O(SO 4 )(IO 3 ) 2 ; a  = 7.2665(4), b  = 18.0115(10), c  = 7.9310(5) Å, β  = 109.7480(10) °, Z = 4 for Bi 2 O(SeO 4 )(IO 3 ) 2 ; and a  = 7.2708(6), b  = 17.9967(14), c  = 7.8998(6) Å, β  = 109.799(2) °, Z = 4 for Bi 2 O(CrO 4 )(IO 3 ) 2 , respectively. All compounds exhibit three-dimensional frameworks that are composed of [Bi 4 O 2 ] 8+ clusters, [IO 3 ] − and [XO 4 ] 2− (X = S, Se, Cr) groups. Bi atoms occur in two different coordination types, showing the stereochemical influence of the Bi 3+ lone electron pair. Title compounds were characterized by infrared spectra, solid state UV–vis–NIR diffuse reflectance spectroscopy and thermogravimetric analysis.