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.