Highly efficient usage of the hydrothermal technique through the one-pot method to construct four Keggin-based compounds containing pendent ligands

Abstract

By utilizing two kinds of pendent organic ligands, four new Keggin-based compounds, [Ag^I₃(bpz)₂(pz)(H₂O)(H₃PMo₁₂O₄₀)₂] (1), [Ag^I₂(bpz)₂(H₃PMo₁₂O₄₀)]·2H₂O (2), [Ag^I₃(btz)₄(PMo₁₂O₄₀)] (3) and [Ag^I₃(btz)₃(PMo₁₂O₄₀)]·H₂O (4) (bpz = 4-butyl-1H-pyrazole, pz = pyrazole, btz = 1-benzyl-1H-(1,2,4)triazole), were synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. Compounds 1 and 2 were obtained in one-pot reaction, as well as compounds 3 and 4. In compound 1, six Ag^I ions are fused by four bpz and two pz molecules to form a hexa-nuclear cycle, with two coordinated water embedding through Ag–O bonds. The three-connected Mo13-containing PMo₁₂ anions connect these cycles alternately to construct 1D chains, which are further linked by four-connected Mo1-containing PMo₁₂ anions to build a 3D framework of 1. Compound 2 contains 1D Ag^I chains, linked by four-connected Mo1-containing PMo₁₂ and two-connected Mo7-containing PMo₁₂ respectively to construct a 3D structure. The pz ligand was not observed in 2. In compound 3, there exist [Ag^I₃(btz)₄]³⁺ subunits, which are alternately connected by PMo₁₂ anions to form a 1D chain. In compound 4, there exists a zigzag Ag-btz chain. The adjacent chains are further linked by Ag–C bonds and a 2D metal–organic layer is constructed. The PMo₁₂ anions link adjacent layers to build a 3D framework of 4. The syntheses of compounds 1 and 2, 3 and 4 prove that the one-pot method under hydrothermal conditions is efficient for pursuing even two more kinds of crystals.