Novel 3D Fluorinated-MOFs: Structure, topology and magnetic properties.

M. A. MONGE; M. C. BERNINI; A.E. PLATERO-PRATS; N. SNEJKO; E. GUTIERREZ-PUEBLA; A. LABRADOR; J. ROMERO; R. SAEZ-PUCHE

Madrid

Congreso; XXII Congress and General Assembly International Union of Crystallography; 2011

IUCr

The metal-organic frameworks (MOFs) are a class of materials that are constantly attracting significant attention not only for their potential applications as functional crystalline materials, but also for their fascinating topologies and structural diversity [1]. The use of flexible and extended ligands contributes to the development of porous frameworks with diverse structural topologies, which, in turn, can lead to obtain varied properties even for the same constitutive units. On the other hand, the magnetic behavior of MOFs, which extended inorganic networks or local paramagnetic centers are linked by diamagnetic linkers that can efficiently mediate magnetic exchange, have evoked considerable interest [2]. However, in MOFs, the magnetism may be introduced through the incorporation of magnetic moment carriers such as paramagnetic metals, or open-shell organic ligands, or both [3]. In this way, we decided to proceed our studies obtaining Fluorinated Metal Organic Frameworks (F-MOFs) constructed of the flexible 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb) as ligand and transition metal ions {Mn(II), Co(II) and Ni(II)}, in order to induce interesting magnetic properties. Besides, we have explored several synthesis conditions to expand the possibilities to get diverse crystal topologies expecting different magnetic properties. Three novel compounds (1a-c) with formula [M3(hfipbb)2(OH)2(H2O)], M = Mn, Co, Ni has been hydrothermally synthesized and completely characterized. The compound 1a´s structure corresponding to the P21/c space group, has been determined by single crystal synchrotron XRD at the ESRF- BM16 beam line, while for compounds 1b and 1c powder diffraction methods were applied in order to obtain both cell parameters and the space groups. Such study indicated the isostructural character of compounds 1a-c. Besides, another two compounds with formula [M2(hfipbb)2(H2hfipbb)], M = Mn (2) and Co (3), were hydrothermally obtained at different synthesis conditions and their structures, corresponding to the C2/c and P2/n space groups, respectively, were determined by conventional single crystal XRD data. Magnetic behavior of compounds 1a-c and 3 has been studied and such results indicate that compounds 1a and 3 have antiferromagnetic interactions while 1b and 1c are ferromagnetics. The topological study of 2 and 3, having the same composition but different crystal structure has also been performed.