Four Keggin-based compounds constructed by a series of pyridine derivatives: synthesis, and electrochemical, photocatalytic and fluorescence sensing properties

Abstract

By introducing a series of pyridine derivatives as organic moieties, four Keggin-based compounds were synthesized, namely [Ag(Py₂Piz)₂(H₂PW₁₂O₄₀)]·2H₂O (1), [Ag₄(AcyPh)₄(H₂SiMo₁₂O₄₀)₂]·2H₂O (2), [Ag₂(Py₃Piz)₂(H₂O)₂(H₃SiMo₁₂O₄₀)₂]·8H₂O (3) and {Ag₄(Py₂TTz)₄[Ag(PMo₁₂O₄₀)₂]}·Ag(Py₂TTz)·2(Py₂TTz)·6H₂O (4) (Py₂Piz = 4,5-bis(2-pyridinyl)imidazole, Py₃Piz = 2-(4-pyridyl)4,5-di(2-pyridinyl)imidazole and Py₂TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole). In compound 1 the [Ag(Py₂Piz)₂]⁺ subunits link Keggin anions through weak Ag-O interactions to form a 1D chain. In compound 2 two mono-supporting Keggin anions are fused by two [Ag(AcyPh)]⁺ subunits to construct a dimer. In compound 3 there is a mono-capped Keggin anion with an [Ag(Py₃Piz)(H₂O)]⁺ subunit. Compound 4 contains a Keggin-dimer linked by an Ag ion. Each dimer is further connected by four sets of [Ag(Py₂TTz)]⁺ lines to construct a 3D framework. All these compounds can be used as nitrite electrochemical sensors. All of them show good photocatalytic activity for MB. In addition, compound 4 shows a selective response to Hg²⁺ ions.