Combination of magnetic susceptibility and electron paramagnetic resonance to monitor the 1D to 2D solid state transformation in flexible metal-organic frameworks of Co(II) and Zn(II) with 1,4-bis(triazol-1-ylmethyl)benzene

Two families of coordination polymers, {M(btix)(2)(OH(2))(2)]·2NO(3)·2H(2)O}(n) M = Co (1), Zn (2), Co-Zn (3); btix = 1,4-bis(triazol-1-ylmethyl)benzene] and {M(btix)(2)(NO(3))(2)]}(n) M = Co (4), Zn (5), Co-Zn (6)], have been synthesized and characterized. The two conformations of the ligand, syn and anti, lead to one-dimensional (1D) cationic chains or two-dimensional (2D) neutral grids. Extrusion of the water molecules of the 1D compounds results in an irreversible transformation into the 2D compounds, which involves a change in conformation of the btix ligands and a rearrangement in the metal environment with cleavage and reformation of covalent bonds. This structural transformation has been followed by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements to monitor the minor modifications that the metal centers suffer.