AbstractKCl72H2SeO3 and CsCl7H2SeO3 have been synthesized using solution evaporation methods from aqueous solution. Both compounds are monoclinic (P2/n and P21/c) and demonstrate new structure types. One symmetrically unique SeO(OH)2 molecule is present in each structure. SeO(OH)2 molecules via strong hydrogen bonds form chains in KCl72H2SeO3 and layers in ?sCl7H2SeO3. The structures of KCl72H2SeO3 and CsCl7H2SeO3 can be described as consisting of ionic KCl chains and CsCl layers incorporated into the covalent- and hydrogen-bonded H2SeO3 matrix. To the best of our knowledge, the cases when selenious acid acts as a contributor to the molecular building blocks of salt-inclusion structures are not known to date.
