Three new POM-based compounds constructed by rigid thiabendazole and flexible bis(pyrazole) ligands: structures and properties for Hg2+ recognition

Abstract

By using mixed rigid and flexible organic ligands, three Keggin based compounds, [Ag₆(tbz)₄(bmz)₂(H₃PW₁₂O₄₀)]·4H₂O (1), [Ag(H₂bdpm)₂(H₂PMo₁₂O₄₀)]·7.5H₂O (2), and [Ag₄(tbz)₂(H₂bdpm)₂(HPMo₁₂O₄₀)]·2H₂O (3) (Htbz = thiabendazole, Hbmz = benzimidazole, H₂bdpm = 1,1′-bis(3,5-dimethyl-1H-pyrazolate)methane), were hydrothermally synthesized and structurally characterized. Through adopting rigid Htbz ligands, compound 1 with hexa-nuclear Ag^I clusters has been obtained. These hexa-nuclear clusters are linked by Keggin anions alternately to form a one dimensional (1D) chain. In compound 2, the organic moiety is the flexible H₂bdpm ligand. The Keggin anions are fused by [Ag(H₂bdpm)₂]⁺ subunits to form a 1D chain. In compound 3, the rigid Htbz and the flexible H₂bdpm cooperate to modify the anions. Two tbz and two H₂bdpm are fused by four Ag^I ions to construct a tetra-nuclear Ag^I cycle. The anions connect these cycles through Ag–O bonds alternately to form a 1D chain. Adjacent chains arrange parallel to build a 2D layer. The chains in the adjacent layers are vertically packed and linked by Ag–O bonds to construct a 3D framework. The electrochemical and photocatalytic properties of the title compounds have been studied. Furthermore, we have also studied the Hg²⁺ recognition properties in a suspension of compounds 1 and 3.