Two extended structures constructed from sandwich-type polyoxometalates functionalized by organic amines

Abstract

Two new compounds constructed from tetra-Ni-substituted sandwich-type polyoxometalates functionalized by organic groups, (NH₄)₂[Ni₄(enMe)₈(H₂O)₂Ni₄(enMe)₂(PW₉O₃₄)₂]·9H₂O (enMe = 1,2-diaminopropane) (1) and Na₂[H₆N₂(CH₂)₆]₂{Ni₄[H₄N₂(CH₂)₆]₂(H₂PW₉O₃₄)₂}·7H₂O (2), have been successfully synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis is carried out on these two compounds (1 and 2), which both crystallize in the triclinic system. Compound 1 represents the first example of a 2D layer structure consisting of the sandwich-type polyoxoanions with six supporting [Ni(enMe)₂]²⁺ moities and two organic functionalized groups. Compound 2 exhibits a 1D chain-like structure based on sandwich-type polyoxoanions and sodium cations, which are further connected into a 2D layer structure viahydrogen-bonding interactions between the 1,6-hexanediamine molecules and the sandwich-type [Ni₄(H₄N₂(CH₂)₆)₂(H₂PW₉O₃₄)₂]^6– polyoxoanions. A magnetic study of the two compounds indicates that intramolecular ferromagnetic Ni–Ni interactions exist in the tetranuclear metal cluster.