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The title compound, {[Ba{Co(H-2L1)}(ClO4)(H2O)]ClO4}n, L1 = 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane, is a one-dimensional coordination polymer. The asymmetric unit consists of a {Ba[Co(H–2L1)](ClO4)(H2O)}+ cationic fragment and a non-coordinating ClO4− anion. In the neutral [Co(H–2L1)] moiety, the cobalt ion is hexacoordinated in a trigonal–prismatic fashion by the surrounding N4O2 donor set. The Ba2+ ion is nine-coordinated and exhibits a distorted [BaO9] monocapped square-antiprismatic geometry, the six oxygen atoms coming from three distinct [Co(H–2L1)] moieties, while the remaining three vertices are occupied by the oxygen atoms of a bidentate perchlorate anion and a water molecule. 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 N4O2 donor set.