Hydrothermal synthesis, crystal structure, thermal behavior and spectroscopic and magnetic properties of two new organically templated fluoro-vanadyl-hydrogenarsenates: (R){sub 0.5}[(VO)(HAsO{sub 4})F] (R: Ethylenediammonium and piperazinium)

Two new fluoro-vanadyl-hydrogenarsenate compounds templated by ethylenediamine and piperazine with formula, (C{sub 2}N{sub 2}H{sub 10}){sub 0.5}[(VO)(HAsO{sub 4})F] (1) and (C{sub 4}N{sub 2}H{sub 12}){sub 0.5}[(VO)(HAsO{sub 4})F] (2), respectively, have been synthesized by using mild hydrothermal conditions under autogenous pressure. The crystal structures have been solved from single-crystal X-ray diffraction data. The phases crystallize in the P2{sub 1}/c monoclinic space group with the unit-cell parameters a=7.8634(4) A, b=7.7658(4) A, c=10.4195(6) A, {beta}=101.524(5){sup o} for compound (1) and a=6.301(1) A, b=10.244(1) A, c=10.248(1) A and {beta}=95.225(1){sup o} for compound (2). These phases exhibit a layered inorganic framework. In both cases, the structure is built from secondary building units (SBU) which are formed by [V{sub 2}O{sub 8}F{sub 2}] edge-shared dimeric vanadyl octahedra, connected by the vertices to two hydrogenarsenate tetrahedra. The repetition of this SBU unit originates sheets along the [1 0 0] direction. The ethylenediammonium and piperazinium cations are located inside the interlayer space. The limit of thermal stability for compounds (1) and (2) is, approximately, 250 and 230 deg. C, respectively. Near this temperature, both phases loose their organic cations and the fluoride anions. The diffuse reflectance spectra confirm the presence of vanadyl ions, in which the vanadium(IV) cations have a d{sup 1} electronic configuration in a slightly distorted octahedral environment. ESR spectra of both phases are isotropic with mean g-values of 1.93 and 1.96 for ethylendiamine and piperazine phases, respectively. Magnetic measurements for (1) and (2) indicate the existence of antiferromagnetic exchange couplings. - Graphical abstract: Polyhedral view of the layered crystal structure of (C{sub 2}H{sub 10}N{sub 2}){sub 0.5} [(VO)(HAsO{sub 4})F].