Thermal and Magnetic Diversity in the Behaviour of the Cu^II‐bdc‐bpa System: 1D, 2D and Interpenetrated 3D Frameworks

Abstract

Metal organic frameworks (MOFs) are crystalline materials based on connections between metal ions through organic ligands. The combination of polycarboxylate anions and dipyridyl ligands is an effective strategy for producing extended structures. In this sense, the combination of bpa with m‐bdc [bpa = 1,2‐bis(4‐pyridyl)ethane, m‐bdc = 1,3‐benzenedicarboxylate] has produced three new CuII‐based networks with different dimensionalities, namely the 1D [Cu(m‐bdc)(bpa)0.5(H2O)dmf]·0.5H2O (1, synthesis based on sonication and slow evaporation), the 2D [Cu6(m‐bdc)6(bpa)6(dmf)3]·8dmf (2, microwave synthesis) and the 3D [Cu4(m‐bdc)4(bpa)2dmf]·dmf (3, microwave synthesis). The three compounds have been structurally characterized by means of single‐crystal X‐ray diffraction, IR and UV/Vis spectroscopy and elemental analysis. An unprecedented CuII dimer has been observed for compound 3. The thermal behaviour of the compounds was analysed by thermogravimetry (TG/DSC) and X‐ray thermodifractometry (TDX), and it was concluded that the dimensionality plays an important role in their thermal properties. Electronic paramagnetic resonance and magnetic susceptibility measurements for compounds 1 and 3 showed that antiferromagnetic interactions exist between the metal ions.

Structural Transformations in the Thermal Dehydration of [Cu2(bpa)(btec)(H2O)4]n Coordination Polymer

“…In a previous publication [39], some of us explored the effect of selecting different non-conventional synthetic methods for the reaction between bpa and benzenedicarboxylate ( m-bdc ). In the course of these studies, microwave-assisted synthesis was found to be the most efficient method for the prepration of frameworks with higher dimensionality.…”

“…In recent years, we have explored non-conventional synthetic methods for the preparation of supramolecular coordination networks that display interesting thermostructural behavior. Previous research indicated the correlation between the synthetic procedures (microwaved-assisted synthesis vs. sonochemistry) employed and the final dimensionality of the network in copper(II) coordination frameworks containing 1,3-benzenedicarboxylic acid and 1,2-bis(4-pyridyl)ethane ( bpa ) ligands [39]. Additional studies on the reversible thermal dehydration of the 1,2,4,5-benzenetetracarboxylic acid ( H 4 btec ) in the ionic [Cu(H 2 dpmd) 2 ][H 2 btec] (H 2 dpmd = dipyridilmethanediol) framework afforded drastic structural changes with associated solvatochromism.…”