The structure and properties of a 3D pillared-layered metal organic framework Cu(II)-diphosphonate

By introducing the second bridging ligand, 4,4′-bipyridyl (4,4′-bipy), the first 3D example of a Cu(II)-diphosphonate-4,4′-bipy metal organic framework (MOF), [Cu3(L)(4,4-bipy)(OH)2] 1 (H4L = H2O3P(C6H4)2PO3H2) was hydrothermally obtained and characterized through powder X-ray diffraction, elemental analysis, IR, and TG-DSC. Single-crystal X-ray diffraction revealed that compound 1 has a 3D MOF structure which is created by a 2D inorganic layer [Cu3O6P2]n through 4,4′-bipy and an organic biphenyl moiety of H4L linkages. In the structure, an inorganic layer and two organic pillars were alternately arranged. The results of fluorescence measurements revealed two decayed emission bands centered at 442 and 374 nm (λex = 236 nm) may be caused by the intraligand π∗–π emission states of the 4,4′-bipy ligand (λem = 442 and 381.5 nm, λex = 236 nm). Magnetism analysis indicated antiferromagnetic interactions between the metal centers within the 1D magnetic chain {–Cu(1)–Cu(2)–Cu(2)–Cu(1)–}n.