Organic–Inorganic Hybrids Constructed from Mixed-Valence Multinuclear Copper Complexes and Templated by Keggin Polyoxometalates

Five organic–inorganic hybrids containing mixed–valence multinuclear copper complexes and Keggin polyoxometalates, [Cu^I₅Cu^II₃(ptz)₈(H₂O)]­[HSiW₁₂O₄₀] (<b>1</b>), [Cu^I₁₀Cu^II₂(ptz)₈(Cl)₃]­[PW₁₂O₄₀] (<b>2</b>), [Cu^I₂Cu^II₄(ptz)₆(OH)­(H₂O)₂]­[PW₁₂O₄₀]·2H₂O (<b>3</b>), Cu^I₂Cu^II₅(ptz)₆(OH)₂SiW₁₂O₄₀·6H₂O (<b>4</b>), and [Cu^I₂Cu^II₅(ptz)₆]­[PMo^V₃Mo^VI₉O₄₀]·8H₂O (<b>5</b>) (ptz = 5-(2-pyridyl)-tetrazole), were hydrothermally synthesized and structurally characterized. Compound <b>1</b> exhibits a three-dimensional (3D) network that features unprecedented double chains consisting of tetranuclear Cu clusters. Compound <b>2</b> displays a 3D network that has unusual Cl-centered hexanuclear Cu clusters and Cl-bridged tetranuclear Cu units. Compound <b>3</b> shows a 3D supramolecular network extended by two-dimensional (2D) grid<b>-</b>like sheets which are composed of mixed-valence multinuclear copper chains and PW₁₂ polyanions. Isostructural compounds <b>4</b> and <b>5</b> exhibit a 3D network consisting of 2D ladder-like copper–ptz layers and SiW₁₂ (PMo₁₂ in <b>5</b>) polyanions. The roles of copper ions with different oxidation states and ptz ligands with different coordination modes in the construction of the copper–ptz frameworks are discussed. Their electrochemical properties were investigated as well