New quaternary alkali metal cadmium selenites, A2Cd(SeO3)2 (A = K, Rb, and Cs) and Li2Cd3(SeO3)4

A series of new alkali metal cadmium selenites, A(2)Cd(SeO3)(2) (A = K, Rb, and Cs) and Li2Cd3(SeO3)(4) have been synthesized in phase pure forms through hydrothermal and solid-state reactions. Structural analyses using single crystal X-ray diffraction indicate that while A(2)Cd(SeO3)(2) and Li2Cd3(SeO3)(4) reveal layered structures consisting of CdO6 and SeO3 polyhedra, their symmetry, bonding modes, and the orientation of lone pairs on Se4+ cations are different. A closer examination suggests that the observed structural variations found in the reported materials are attributed to the structure-directing effect of alkali metal cations with different sizes. Scanning electron microscopy/energy dispersive analysis by X-ray, thermogravimetric analysis, Infrared and UV-vis diffuse reflectance spectroscopy, transformation reactions under hydrothermal conditions, and local dipole moment calculations for the reported materials are also reported.