Two Cobalt(II) 5-Aminoisophthalate Complexes and Their Stable Supramolecular Microporous Frameworks

Two stable supramolecular microporous cobalt(II) polymers, namely [Co(HAIP)2]n·3nH2O (1) and [Co(AIP)(H2O)]n
(2), AIP = 5-aminoisophthalate, were hydrothermally synthesized and characterized by single-crystal X-ray diffraction,
IR spectra, thermogravimetric analyses, and variable-temperature magnetic susceptibility measurements. The two
complexes are constructed from the same Co2(CO2)2 SBU, which is extended into a 1D chain in 1 and a 2D layer
in 2. As a result, 1 and 2 are 2D and 3D coordination polymers, respectively. The 3D supramolecular network of
complex 1 is held up by strong hydrogen bonds formed between carboxylate groups and shows very high stability
when the free H2O molecules are removed, indicating an extraordinarily stable H-bonding system. Upon water
ligands being liberated, complex 2 becomes a stable microporous solid with coordination-unsaturated Co centers.
The behavior of the susceptibility curve of 1 suggests the occurrence of an interesting intrachain antiferromagnetic
coupling between the Co(II) ions and the presence of a significant orbital contribution, whereas the features of 2
indicate an antiferromagnetic coupling with TN = 3.5 K and a long-range antiferromagnetic order with a field-induced magnetic transition.