Crystal structure of the Ba II -based Co II -containing one-dimensional coordination polymer poly[[aqua{μ 4 -2,2'-[(4,10-dimethyl-1,4,7,10-tetra-aza-cyclo-dodecane-1,7-di-yl)bis(methylidene)]bis-(4-oxo-4 H -pyran-3-olato)}-perchloratocobaltbarium] perchlorate].

The title compound, {[Ba{Co(H-2 L1 )}(ClO4 )(H2 O)]ClO4 } n , L1 = 4,10-bis-[(3-hy-droxy-4-pyron-2-yl)meth-yl]-1,7-dimethyl-1,4,7,10-tetra-aza-cyclo-dodeca-ne, is a one-dimensional coordination polymer. The asymmetric unit consists of a {Ba[Co(H-2 L1 )](ClO4 )(H2 O)}+ cationic fragment and a non-coordinating ClO4 - anion. In the neutral [Co(H-2 L1 )] moiety, the cobalt ion is hexa-coordinated in a trigonal-prismatic fashion by the surrounding N4 O2 donor set. The Ba2+ ion is nine-coordinated and exhibits a distorted [BaO9 ] monocapped square-anti-prismatic geometry, the six oxygen atoms coming from three distinct [Co(H-2 L1 )] moieties, while the remaining three vertices are occupied by the oxygen atoms of a bidentate perchlorate anion and a water mol-ecule. A barium-μ2 -oxygen motif develops along the a axis, connecting symmetry-related dinuclear BaII -CoII cationic fragments in a wave-like chain, forming a one-dimensional metal coordination polymer. Non-coordinating ClO4 - anions are located in the space between the chains. Weak C-H⋯O hydrogen bonds involving both coordinating and non-coordinating perchlorate anions build the whole crystal architecture. To our knowledge, this is the first example of a macrocyclic ligand forming a BaII -based one-dimensional coordination polymer, containing CoII ions surrounded by a N4 O2 donor set.