Synthesis, structure, and properties of the multinuclear cobalt core POM Na14[Co3O(H2O)(A-α-PW9O34)2]·~29.5H2O.

• The sandwich POM Na 14 [Co 3 O(H 2 O)(A-α-PW 9 O 34)2]·~29.5 H 2 O was synthesized. • Single crystal X-ray diffraction reveals a multinuclear [Co 3 O 13 core. • Efficient electron transfer is observed by cyclic voltammetry, with three reversible redox peaks. • Antiferromagnetic behavior is observed at higher temperatures, with a ferromagnetic transition at lower temperatures. A new trimeric Co(II) containing Keggin trilacunary polyoxometalate (POM) sandwich complex, Na 14 [Co 3 O(H 2 O)(A-α- PW 9 O 34) 2 ·~29·.5H 2 O (Na14-1) was synthesized by the reaction of [Co 2 (μ- OH 2)(O 2 CCMe 3) 4 (HO 2 CCMe 3) 4 and Na 9 [A-α-PW 9 O 34 ·7H 2 O. The compound has been characterized by elemental analysis, FTIR, TGA and single crystal XRD (Triclinic space group P- 1, a = 12.2204(8) Å, b = 16.7035(11) Å, c = 23.3466(16) Å, α = 78.448(2)°, β = 80.551(2)°, γ = 78.448(2)° and Z = 2). The POM was electrochemically active and its behavior was studied by cyclic voltammetry at different scan rates. Bond valence sum (BVS) calculation was used to determine the oxidation state of Co. The magnetic susceptibility study indicated antiferromagnetic interactions between Co(II) ions and at lower temperature ferromagnetic behavior dominant in the structure. [ABSTRACT FROM AUTHOR]