A series of 0D to 3D Anderson-type polyoxometalate-based compounds obtained under ambient and hydrothermal conditions

Abstract

Through using flexible ethanediamine (en) and bis(triazole) ligands, a series of Anderson POM-based compounds, [{Cu^II₂(en)₄}{Al(OH)₆Mo₆O₁₈}]₂·[{Cu^II(en)₂}{Al(OH)₆Mo₆O₁₈}]₂·47H₂O (1), [{Cu^II₂(en)₄}{Cr(OH)₆Mo₆O₁₈}]₂·[{Cu^II(en)₂}{Cr(OH)₆Mo₆O₁₈}]₂·47H₂O (2), [{Cu^II_5/2(en)₃(μ₂-OH)₂}{Al(OH)₆Mo₆O₁₈}]·H₂O (3), [{Cu^II(bte)₂(H₂O)}{HCr(OH)₆Mo₆O₁₈}]·6H₂O (4), [{Cu^II₃(btp)₂(H₂O)₄}{Cr(OH)₆Mo₆O₁₈}₂]·6H₂O (5), [{Cu^I₂(btp)}{Cr(OH)₆Mo₆O₁₈}{K(H₂O)₂}] (6) and [Cd₃(btp)₂(H₂O)₁₄]H₃[Cr(OH)₆Mo₆O₁₈]₃·16H₂O (7) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane and btp = 1,3-bis(1,2,4-triazol-1-yl)propane), were synthesized and structurally characterized. In isostructural compounds 1 and 2, the 2D grid-like layers and 1D metal–organic chains arrange alternately through hydrogen bonding interactions. Compound 3 has a 2D grid-like layer with Anderson anions linked by mono- and binuclear Cu^II clusters alternately. Compound 4 shows a 1D cycle-connecting-cycle metal–organic chain with anions hanging on one side. In compound 5, the Cr2-anions are connected by [Cu₃(btp)₂]⁶⁺ subunits to form a 2D layer. The Cr1-anions link adjacent layers to build a 3D framework. In 6, the anions link ladder-like Cu–btp chains to construct a 3D framework, with K ions embedding in the channels. Compound 7 exhibits a discrete structure with [Cd₃(btp)₂(H₂O)₁₄]⁶⁺ as a counter cation. The successful syntheses of 1–7 reveal that both the appropriate ambient and hydrothermal conditions can induce Anderson-based compounds with ease. Furthermore, we also studied the electrochemical and photocatalytic properties of the title compounds.