Hydrothermal synthesis and characterization of a new 3D vanadium(III) phosphite (C4H8N2H4)0.5(C4H8N2H3)[V4(HPO3)7(H2O)3]1.5H2O

A new vanadium(III) phosphite, (C4H8N2H4)(0.5)(C4H8NH3)[V-4(HPO3)(7)(H2O)(3)]1.5H(2)O, has been synthesized hydrothermally by using V2O5, H3PO3 as reactants, piperazine as the structure-directing agent. The as-synthesized product was characterized by powder X-ray diffraction, IR spectroscopy, inductively coupled plasma. analysis, thermogravimetric analysis, and SQUID magnetometer. Single-crystal X-ray diffraction analysis shows that the title compound crystallized in the trigonal space group P3cl (No. 165) with the parameters: a = 13.4678(4) Angstrom, c = 18.3171(8) Angstrom, V = 2877.27(17) Angstrom and Z = 4. Its structure is built up by alternation of octahedral VO6 or VO5(H2O) and pseudo-pyramidal HPO3 units to form infinite 2D layers, and these layers are interconnected by sharing vertex-oxygen with octahedral VO6 units to generate a 3D open-framework structure with 12-membered ring channels in a and b directions, respectively, where there exist entrapped diprotonated and mono-protonated piperazine cations, and water molecules. Magnetic measurement indicates that paramagnetic behavior is observed down to 4 K. (C) 2004 Published by Elsevier Inc.