Four nodal self-catenated [{Ni8(Bpy)16}V24O68]·8.5(H2O), combining three dimensional metal–organic and inorganic frameworks

Abstract

The chiral three dimensional crystal structure of [{Ni₈(Bpy)₁₆}V₂₄O₆₈]·8.5(H₂O) is the first example of a hybrid vanadate combining a three dimensional metal–organic subnet with a three dimensional inorganic framework. The metal–organic framework consists of 3D + 2D polycatenation of a 3D “cds” like net and two 2D “sql” layers. The vanadium oxide subunit is a complex chain constructed from V₅O₁₅ cycles linked through a single tetrahedron. The vanadate chains are located in the channels of the metal–organic framework, and corner linked to the nickel metal centres giving rise to an unprecedented four nodal self-catenated framework. Moreover, as far as we as concerned, this is the first vanadate in which the V₅O₁₅ cycles has been isolated in the solid state. The crystallization water molecules are partially encapsulated between the organic ligands and the inorganic framework. The loss of crystallization water molecules gives rise to a contraction of the 0.6% of the unit cell volume. The IR spectrum shows the characteristic bands of the vanadium oxide subunit, and the bpy ligand. The BET measurement gives rise to a type III profile, (3.7 cm² g⁻¹), suggesting weak adsorbate-adsorbent interactions. The thermal evolution of the magnetic susceptibility is attributed to the zero-field splitting for eight non interacting Ni(II) cations.