Zn(II) and Cu(II)-based coordination polymers and metal organic frameworks by the use of 2-pyridyloximes and 1,3,5-benzenetricarboxylic acid.

Abstract

The simultaneous use of 2-pyridyl oximes (pyridine-2 amidoxime, H2pyaox; 2-methyl pyridyl ketoxime, Hmpko) and 1,3,5-benzenetricarboxylic acid (H3btc) provided access to five new compounds, namely [Zn(H2btc)2(H2pyaox)2]¿2H2O (1¿2H2O), [Zn(Hbtc)(H2pyaox)2]n (2), [Cu(Hbtc)(H2pyaox)]n (3), [Cu(Hbtc)(HmpKo)]n (4) and [Cu2(Hbtc)2(Hmpko)2(H2O)2]¿4H2O (5¿4H2O). Among them, 3 is the first example of a metal-organic framework (MOF) containing H2pyaox. Its framework can be described as a 3-c uninodal net of hcb topology with the layers being parallel to the (1,0,1) plane. Furthermore, 3 is the third reported MOF based on a 2-pyridyl oxime in general. 2 and 4 are new members of a small family of coordination polymers containing an oximic ligand. 1-5 form 3D networks through strong intermolecular interactions. Dc magnetic susceptibility studies were carried out in a crystalline sample of 3 and revealed the presence of weak exchange interactions between the metal centres; the experimental data were fitted to a theoretical model with the fitting parameters being J = −0.16(1) cm−1 and g = 2.085(1). The isotropic g value was also confirmed by electronic paramagnetic resonance (EPR) spectroscopy. Reactivity studies were performed for 3 in the presence of metal ions; the reaction progress was studied and discussed for Fe(NO3)3 by the use of several characterization techniques, including single crystal X-ray crystallography and IR spectroscopy.