Synthesis, crystal structure and properties of sandwich type compounds based on {AsW9} and a hexa-nuclear unit with three supporting TM–triazole complexes

Abstract

Three hexa-nuclear substituted sandwich-type arsenotungstates, Na₆[{Na(H₂O)}₃{Ni(Htaz)}₃(AsW₉O₃₃)₂]·4H₂O (1), Na₆[{Na(H₂O)}₃{Co(Htaz)}₃(AsW₉O₃₃)₂]·8H₂O (2), and Na₆[{Na(H₂O)_0.5}₃{Mn(Htaz)}₃(AsW₉O₃₃)₂]·11H₂O (3) (taz = 1,2,4-1H-triazole), have been synthesized and structurally characterized. Basic frameworks of 1–3 are constructed from sandwich-type [{Na(H₂O)_n}₃{M(Htaz)}₃(AsW₉O₃₃)₂]⁶⁻ (n = 1 or 0.5) anions and sodium cations. The transition metal ions M²⁺ and Na⁺ in the central belt are coordinated by α-[AsW₉O₃₃]⁹⁻ units, taz, and water molecules to form {MO₄(Htaz)} and {NaO₄(H₂O)_m} (m = 1 or 2) segments in which M²⁺ ions are modified with Htaz ligands. These fragments connect alternately in an edge-sharing mode forming a six-membered ring. Such a triazole coordinated six-nuclear cluster is first observed in a sandwich-type arsenotungstate system. The compounds 1–3 exhibit good electrocatalytic activity to reduce hydrogen peroxide and antiferromagnetic interactions between the trinuclear M(II) clusters. In addition, complex 1 has a potent inhibition effect on cell proliferation of HeLa cells.