Three multi-nuclear clusters and one infinite chain induced by a pendant 4-butyl-1H-pyrazole ligand for modification of Keggin anions†
By utilizing pendant 4-butyl-1H-pyrazole (Hbpz) with an alkyl “tail” –(CH2)3CH3, four Keggin-based complexes containing different transition metal multi-nuclear clusters and an infinite chain were hydrothermally synthesized and structurally characterized, [CuI4(bpz)4(pz)2(H6PW11CuIIO39)2]·10H2O (1), [CuII2(bpz)2(H2O)2(H3PCu0.5Mo11.5O40)]·3H2O (2), [Ag3(bpz)2(pz)(H4SiW12O40)]·4H2O (3) and [Ag5(bpz)4(H5/2PMo12O40)2]·6H2O (4) (pz = pyrazole). Compound 1 contains a tetra-nuclear cluster [CuI4(bpz)4(pz)2]2−, in which four CuI ions are fixed by four bpz and two pz ligands. These clusters are linked by Keggin anion dimers to form a 2D layer. In compound 2, the ptz ligands fuse the CuII ions and an infinite 1D metal–organic chain is constructed with the Keggin anions hanging up and down covalently. Compound 3 has a planar triangle tri-nuclear cycle [Ag3(bpz)2(pz)] with three AgI as cores. These cycles build a 3D framework of 3 through the further linkages of Keggin anions and Ag–Ag bonds. In compound 4, there exist discrete [Ag5(bpz)4]+ clusters with four bpz ligands fused by five AgI cores, which are linked by Keggin anions alternately to form a 1D chain. Adjacent chains share the Ag–O bonds and a 2D layer is constructed. The bpz ligand is firstly introduced into the POM field and its successive two N donors are essential for the construction of multi-nuclear clusters and an infinite chain of 1–4. Additionally, the electrochemical and photocatalytic properties of the title compounds have been investigated.