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(OH2)2]·2NO3·2H2O}n [M = Co (1),
Zn (2), Co–Zn (3); btix = 1,4-bis­(triazol-1-ylmethyl)­benzene]
and {[M­(btix)2(NO3)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.