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, [Cu(I)4(bpz)4(pz)2(H6PW11Cu(II)O39)2]·10H2O (1), [Cu(II)2(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 Cu(I)4(bpz)4(pz)2, in which four Cu(I) 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 Cu(II) 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 Ag(I) 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 Ag(I) 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.