A novel three-dimensional heterometallic coordination polymer: poly[[diaquadi-μ₃-chlorido-μ₂-chlorido-tri-μ₃-nicotinato-tricopper(I)gadolinium(III)] hemihydrate]

In the title polymeric heterometallic compound, {[Cu₃Gd(C₆H₄NO₂)₃Cl₃(H₂O)₂]·0.5H₂O}_n, comprising copper(I) and gadolinium(III) cations bridged by nicotinate (nic) ligands and chloride anions, the Gd^III centers display a bicapped trigonal prismatic geometry, defined by six carboxylate O atoms and two water molecules. For copper(I), one Cu center is three-coordinated by three chloride ions and displays a trigonal–planar geometry; the other two Cu centers are four-coordinated and display a very distorted tetrahedral geometry. The chloride anions act in μ₂- and μ₃-bridging modes, linking the Cu^I ions into an infinite chain. The nic ligand exhibits a tridentate coordination mode, with the carboxylate O atoms linking to two Gd^III ions and the N atom linking to one Cu^I ion. Thus, a novel three-dimensional heterometallic coordination polymer is constructed from Gd–carboxylate subunits and Cu—Cl chains. In addition, intra- and intermolecular O—H...O and O—H...Cl hydrogen bonds are also observed within the three-dimensional structure. Topologically, the framework represents an unusual 3,6-connected (4.8²)₃(4¹⁰.6⁵) net.