Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M(AsWO)(AsOH)] (M = Cr, Fe, Sc, In, Ti, Mn) and Their Magnetic Properties.

Six arsenic(III)-capped 12-tungsto-2-arsenates(III) of the type [M(AsWO)(AsOH)] (M = Cr, ; Fe, ; Sc, ; In, ; Ti, ; Mn, ) have been synthesized in aqueous medium by direct reaction of the elements using a one-pot strategy and structurally characterized by FT-IR spectroscopy, single-crystal XRD, and elemental analysis. Polyanions - are comprised of two octahedrally coordinated guest metal ions M sandwiched between two {AsW} units, resulting in a structure with point-group symmetry. Polyanions - contain tri- and tetravalent metal ion guests M (M = Cr, Fe, Sc, In, and Ti, respectively), and they have one {AsOH} group grafted on each {AsW} unit, whereas the divalent Mn-containing derivative has two such {AsOH} groups grafted on each {AsW} unit. Magnetic studies on polyanions - over the temperature range 1.8-295 K and magnetic fields of 0-7 T confirmed that they are diamagnetic. On the other hand, polyanions , , and are strongly magnetic and follow the Curie-Weiss law above 30 K. The susceptibility plots of and exhibit broad peaks suggesting short-range antiferromagnetic ordering, while the very weak antiferromagnetic ordering of is overshadowed by traces of a paramagnetic impurity. The magnetization data of , , and at 1.8 K over 0-7 T were analyzed by using the Heisenberg exchange procedure. Small (negative) values of the obtained values help in understanding the absence of long-range antiferromagnetic ordering.