Metal-organic framework: Structure and magnetic properties of [Cu3(BTC)2 (L)X.(CuO)y]n (L=H2O, DMF)

The compounds [Cu-3(BTC)(2)(L)(x).(CuO)(y)], with BTC (benzene 1,3,5-tricarboxylate) and L (H2O or DMF) were prepared using electrochemical synthesis. Structural and morphologic characterizations were performed by X-ray diffraction and scanning electronic microscopy. The [Cu-3(BTC)(2) (L)(x).(CuO)(y)] contain dimeric [Cu-2(O2CR)](4) units with three possible spin configurations arising from Cu(II) 3d(9) states and Cu-Cu delta bond. We observed an unusual very strong antiferromagnetic coupling in temperatures ranging from 100 K to 350 K for [Cu-3(BTC)(2).(H2O)(3). (CuO)(y)](n). The inverse susceptibility versus temperature shows a linearity from 20 K up to 65 K fitting the Curie-Weiss law, for L = DMF. The CW X-band electron paramagnetic resonance spectroscopy (EPR) was important to explore the coordination state for DMF in the network. It was observed that DMF is located in an equatorial geometry of the coordination network experimenting interactions from the nitrogen and copper ions.