Zn II and Cu II -Based Coordination Polymers and Metal Organic Frameworks by the of Use of 2-Pyridyl Oximes and 1,3,5-Benzenetricarboxylic Acid.

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. [ABSTRACT FROM AUTHOR]