Synchrotron study of poly[[di-μ-aqua-(μ-2,2'-bipyridyl-5,5'-dicarboxyl-ato)di-potassium] dihydrate]

The title compound, {[K(2)(C(12)H(6)N(2)O(4))(H(2)O)(2)]·2H(2)O}(n), forms a three-dimensional coordination polymer in the solid state. The asymmetric unit consists of one K(+) ion, half of a 2,2'-bipyridyl-5,5'-dicarboxyl-ate ligand, one coordinated water mol-ecule and one solvent water mol-ecule. The K(+) ion is 7-coordinated by the oxygen atoms of two water mol-ecules and by five oxygen atoms of four carboxyl-ate groups, one of which is chelating. The extended structure can be described as a binodal network in which each K(+) is a six-connected node, bonding to four carboxyl-ate groups and two bridging water mol-ecules, and the 2,2'-bipyridyl-5,5'-dicarboxyl-ate linkers are eight-connected nodes, with each carboxyl-ate group bridging four metal centers. Overall, this arrangement generates a complex network with point symbol {3(4).4(12).5(12)}{3(4).4(4).5(4).6(3)}(2). Both of the bridging water mol-ecules participate as donors in hydrogen-bonding inter-actions; one to solvent water mol-ecules and a second to an oxygen atom of a carboxyl-ate group.