Structure and host–guest properties of the nanoporous diaquatetrakis(p-nitrobenzoato)dicopper(II) framework

Abstract

[Cu₂(p-O₂NC₆H₄CO₂)₄(H₂O)₂]·Me₂CO has been prepared and characterized by single crystal X-ray diffraction. The Cu–Cu distance is 2.608(1) Å with the four p-nitrobenzoate ligands coordinated in bidentately bridging fashion, such that the copper atoms have a square pyramidal coordination. It possesses a framework structure with continuous channels parallel to the c axis with an opening size of ≈5.6 × 7.9 Å, giving a solvent accessible volume of 22% of the crystal volume. The framework remains intact and crystalline after removal of the included acetone molecule, as determined by X-ray powder diffraction. It is shown, by thermogravimetric measurements, that also benzene and water guest molecules can reversibly be incorporated and released. For comparison, [Cu₂(p-O₂NC₆H₄CO₂)₄(EtOH)₂] was prepared and characterized by single crystal X-ray diffraction. Here, the channels are occupied by the axial ethanol ligands.