Crystal architecture and magnetic properties of four transition-metal adipate coordination polymers

The crystal structures have been determined and the magnetic properties investigated for four novel [M-II(A)(H2O)(m)](n) polymeric complexes, where M-II=Cd-II, Cu-II or Ni-II, m=2-4 and A=adipate dianion. In [Cd(A)(H2O)(2)](n) 1, [Cu(A)(H2O)(2)](n) 2 and [Ni(A)(H2O)(4)](n) 4 the combination of the metal cation with the dicarboxylate ligand leads to the formation of infinitive chains; still the co-ordinated water molecules and the carboxylate oxygen atoms collaborate to hydrogen-bond the chains into 3-D structures. Each cadmium(II) and nickel(II) ion in 1 and 4 is coordinated in an octahedral geometry to carboxylate and water molecules. The coordination sphere around copper(II) ions in 2 is square planar. The structure of 3, [Cu-3(A)(2)(OH)(2)(H2O)(4)](n), is made up of ribbons linked to neighboring ones by hydrogen bonds. Each ribbon is composed of 2 crystallographically independent metal centers, Cu(1) and Cu(2), which exhibit octahedral and square pyramidal coordination geometries, respectively. Weak antiferromagnetic interactions were observed for 2, and 3 (singlet-triplet energy gap values of -2.3 and -54.5 cm(-1), respectively) and isolated nickel(II) ions for 4. An interpretation of the magnetic behavior was attempted. The strategy for the assembly of 1-D metal-organic chains into 3-D structures, with the use of coordinated water molecules as hydrogen bond donors and carboxylate oxygens as hydrogen bond acceptors, is also discussed.