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Aza-heterocyclic ligand assisted assembly of new cobalt MOFs with pcu and graphite related structures
Debajit Sarma1, Vishwas Srivastava, Srinivasan Natarajan
1Framework solids Laboratory, Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, 560012, India.
Abstract:
A hydrothermal reaction of a mixture of cobalt salt, 5-nitro isophthalic acid and triazole (compound I), 3-aminotriazole (3-AT) (compound II) and 3,5-diaminotriazole (compound III) at 220 °C for a day resulted in the isolation of three different, but related, compounds containing cobalt clusters. The three-dimensional compounds have Co(5) (compound-I) and Co(4) (compound-II and compound-III) clusters connected through the carboxylate and triazolate forming structures with pcu net (compound-I and compound-II) and a graphite-related net (compound-III). The water molecules (coordinated and lattice) can be readily re-adsorbed by the structure of compound-I, whereas the removal of the water molecule leads to a collapse of the structures of compound-II and compound-III. The TGA studies suggest the possibility of an intermediate structure for compound-1, which was investigated using in situ single crystal to single crystal (SCSC) transformations. The identification of an intermediate structure during the dehydration/hydration cycle in compound-I is important and provides important pointers about the dynamics of the water molecules in these compounds. Compound-I was also investigated in detail using a variety of spectroscopic techniques such as IR, UV-Vis spectroscopy etc. Magnetic studies on the synthesized compounds indicate anti-ferromagnetic behavior.
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