A series of 3D PW12O403−-based AgI–bis(triazole) complexes containing different multinuclear loops: syntheses, structures and properties

Abstract

Four [PW₁₂O₄₀]³⁻ (PW₁₂)-based inorganic–organic hybrid compounds constructed from Ag^I ions and flexible bis(triazole) ligands with different spacer lengths, [Ag₈(btp)₄(H₂O)₂(HPW^VI₁₀W^V₂O₄₀)₂]·H₂O (1), [Ag₄(btb)₂(HPW^VI₁₀W^V₂O₄₀)] (2), [(btb)(H₃PW₁₂O₄₀)]·6H₂O (3) and [Ag₅(btx)₄(PW^VI₁₀W^V₂O₄₀)] (4), (btp = 1,3-bis(1,2,4-triazol-1-yl)propane, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, btx = 1,6-bis(1,2,4-triazol-1-yl)hexane), have been successfully isolated in the pH range 0.5–2.0 under hydrothermal conditions and characterized by single crystal X-ray diffraction analysis. In compound 1, the btp with a shorter spacer –(CH₂)₃– was used, and the 2D Ag^I–btp wave layers containing tetra-nuclear loops have been obtained, which were further extended into a 3D hamburger-style framework by two types of PW₁₂ inorganic linkages. In compound 2, the btp ligand was replaced by btb with a longer spacer –(CH₂)₄–, thus a 2D Ag^I–btb grid layer containing two types of multinuclear loops was obtained. The PW₁₂ anions reside in the void of a large hexa-nuclear loop and as octa-dentate inorganic linkages connect these 2D grid layers to construct a 3D framework. Compound 3 was synthesized under the same conditions as 2 except for a different crystallization time, which only exhibits a supramolecular structure constructed from protonated PW₁₂ and btb molecules. The btx molecule with the longest –(CH₂)₆– spacer was utilized in compound 4, an interesting 3-fold interpenetrating 2D Ag^I–btx network containing large dodeca-nuclear loops formed, which was further linked by the six-connected PW₁₂ anions to construct a 3D skeleton. The influences of –(CH₂)_n– spacers as well as the pH value and crystallization time on forming and tuning different 3D Ag^I/POM-based compounds containing different multinuclear loops have been discussed. Moreover, the electrochemical properties and photochemical catalysis of these four compounds have also been investigated.