Inorganic−Metalorganic Hybrids Based on Copper(II)-Monosubstituted Keggin Polyanions and Dinuclear Copper(II)−Oxalate Complexes. Synthesis, X-ray Structural Characterization, and Magnetic Properties

Reaction of in situ generated copper(II)-monosubstituted Keggin polyoxometalates and copper(II)−bipyridine−oxalate
complexes in the corresponding alkaline acetate buffer led to the formation of hybrid metal organic−inorganic
compounds K2[{SiW11O39Cu(H2O)}{Cu2(bpy)2(H2O)2(μ-ox)}2]·14H2O (1), K14[{SiW11O39Cu(H2O)}{Cu2(bpy)2(μ-ox)}]2[SiW11O39Cu(H2O)]·55H2O (2), (NH4)4[{SiW11O39Cu(H2O)}{Cu2(bpy)2(μ-ox)}]·10H2O (3), and Rb4[{SiW11O39Cu(H2O)}{Cu2(bpy)2(μ-ox)}]·10H2O (4). Their structures have been established by single-crystal X-ray diffraction.
The main structural feature of these compounds is the presence of copper(II)-monosubstituted α-Keggin polyoxoanions
as inorganic building blocks, on which the μ-oxalatodicopper metalorganic blocks are supported. Compound 1
contains the discrete hybrid polyanion [{SiW11O39Cu(H2O)}{Cu2(bpy)2(H2O)2(μ-ox)}2]2-, whereas the polymeric
hybrid polyanion [{SiW11O39Cu(H2O)}{Cu2(bpy)2(μ-ox)}2]n4n- gives a monodimensional character to compounds
2−4. Magnetic and EPR results are discussed with respect to the crystal structure of the compounds. DFT calculations
on both the [Cu2(bpy)2(H2O)4(μ-ox)]2+ cationic complex and the metalorganic blocks have been performed in order
to determine the optimized geometry and the magnetic coupling constants, respectively.