A novel polyoxovanadate (POV), [Zn(2,2(')-bPY)(3)](4)[(ppz){{Zn(tepa)}(2)ZnAs8V13O41(H2O)}(2)][As8V14O4 2(0.5H(2)O)](2)center dot 4H(2)O (1, 2,2(')-bpy = 2,2(')-bipyridine, ppz = piperazine, tepa = tetraethylenepentamine), has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectra, thermogravimetric analysis, magnetic measurement, and single-crystal X-ray diffraction analysis. Crystal data for 1: orthorhombic, Aba2, a = 28.3414(14) angstrom, b = 27.9995(16) angstrom, c = 41.5819(16) angstrom, V = 32997(3) angstrom(3), Z = 4, rho = 2.264 mg center dot cm(-3). X-ray structure analysis shows that the structure of 1 consists of one unique zinc-substituted POV dimer and two POV monomers. Interestingly, the formation of the zinc-substituted POV dimer involves two new in situ ligand reactions under hydrothermal conditions, the intermolecular and intramolecular deamination coupling reactions of dien. Magnetization measurement revealed the presence of antiferromagnetic interaction between V-IV ions in 1.