The new vanadium phosphate H2N(CH2CH2)(2)NH2[(VO)(4)(H2O)(4)(HPO4)(2)(PO4)(2)], (1), was prepared from the reaction of VCl4:H3PO4:1,4-diaminopiperazine hydrochloride:tetra-n-buytlammonium hydroxide:H2O in a mole ratio of 1:8.9:4.4:5.2:2268 in a sealed glass tube for 3 h at 200 degrees C. Phosphate 1 crystallizes in the acentric monoclinic space group Im with a = 7.025(1), b = 9.470(2), and c = 16.570(3)Angstrom, beta = 96.03(3)degrees, V = 1096.3 (6) Angstrom(3), Z = 2, and R (R(W)) = 0.0517 (0.0595) and possesses a three dimensional (3-D) covalently bonded structure comprised of a vanadium phosphate net with occluded organic cations occupying tunnels within the oxide framework. The structure can be qualitatively described as a severely defected VOPO4 structure type, with phosphate 1 displaying several different VO6 environments that can be envisioned as related to the infinite {O=V ... O}(n) strings present in VOPO4 : (a) infinite 1-D chains of VO6 octahedra sharing opposite vertices with the remaining four vertices connected to {PO4} tetrahedra just as in VOPO4; (b) 1-D chains as in point a but with every other octahedron missing with the distorted octahedral coordination requirements satisfied by the addition of an aquo ligand trans to the V=O group; (c) 1-D chains as in point a but with every other one missing and each V atom coordinated to three aquo ligands; (d) a region that would be occupied by a 1-D chain in VOPO4 but is totally missing and is occupied by the organic dication. As a result, some of the {PO4} tetrahedra are either absent or possess P-OH groups to compensate for the missing V atoms.