Di-, Tetra-, and Hexanuclear Hydroxy-Bridged Copper(II) Cluster Compounds: Syntheses, Structures, and Properties

Self-assembly reactions of copper (II) ions, dicarboxylate (adipate or terephthalate) and terminal ligands (4,4′-bipyridine or phenanthroline) yielded three hydroxy-bridged Cu(II) cluster complexes: [Cu(phen)(OH)(H2O)]2·(C8H4O4)·8H2O (1), [Cu4(bpy)4(OH)4(H2O)2]·(C8H4O4)2·6H2O (2) and [Cu6(bpy)6(OH)6(H2O)2]·(C6H8O4)3·23H2O (3) (phen = phenanthroline, bpy = 2,2′-bipyridine, C8H6O4 = terephthalic acid, C6H10O4 = adipic acid). Single crystal X-ray diffraction analyses reveal that complex 1 is a discrete dinuclear Cu2O2 motif, 2 presents a discrete chairlike tetranuclear copper(II) Cu4O4 core formed by two Cu2O2 units, and 3 assumes a discrete hexameric copper(II) Cu6O6 cluster consisting of three Cu2O2 units. The polynuclear structures are generated from the Cu(II) ions linked by the µ2- and/or µ3-OH groups. In 1−3, all Cu(II) ions show square pyramidal coordination geometry, and the dicarboxylate ions act as counteranions to keep the whole structure neutral. Thermogravimetric analyses (TGA) and magnetic properties of 1−3 were studied, respectively.