In this contribution we described the structures of four new Mg-benzene-1,3,5-tricarboxylates, NICS-n (National Institute of Chemistry, n = 3 – 6) with different dimensionalities. NICS-3 is 0-dimensional molecular complex with formula Mg(H2BTC)2(H2O)4, NICS-4 (Mg3(BTC)2(H2O)12) represents 1-dimensional chain-like structure, NICS-5 (Mg2(BTC)(OH)(H2O)4.2H2O) 2-dimensioan layered structure and NICS-6 3-dimensional structure with formula Mg3(BTC)2. We showed that at solvothermal conditions, crystallization of these phases can be tuned by changing ethanol/water solvent composition. When using pure water, NICS-3 is crystallized. NICS-4 and NICS-5 are formed using mixture of solvents with EtOH/H2O molar ratio of 0.3 and 0.4-0.7, respectively. Crystallization in pure ethanol leads to the formation of NICS-6. By NMR spectroscopy we proved that larger metal-based units are formed in the absence of ligand in ethanol-rich solvent. These units are connected to BTC ligand already at the very beginning of solvothermal process into metal-organic metastable phases, which do not resemble the final structures.
COBISS.SI-ID: 5290522
In this contribution we described the investigations on structure dynamics of calcium-1,4-dicarboxylate (BDC) with the formula Ca(BDC)(DMF)(H2O) upon thermal treatment up to 500 °C. With the use of spectroscopic techniques (IR, NMR, XAS) we determined that during the heating process, the removal of DMF molecules from the material occurs in two steps and that this process governs structural changes of calcium terephthalate up to 400 °C. By powder X-ray diffraction (XRD) we determined the structure of high-temperature phase which is formed at 400 °C, enabling us to determine the mechanism of the structure transformation. The removal of the coordinated DMF molecules, which fill the channels of the structure, does not cause only the emptying of the channels, but also leads to the complete structural transformation into non-porous structure. On the high-temperature phase e also investigated the process of hydration, leading to the formation of chain-like structure with the formula Ca(BDC)(H2O)3. This structure is reversibly transformed back to the 3-dimensional high-temperature phase. This investigation represents an unique insight into the structural dynamics of calcium-based MOFs and clarifies the reasons for crystallization into non-porous structures, which represents general drawback of Ca-MOFs.
COBISS.SI-ID: 36628485
A new layered Ca-succinate coordination polymer, poly[[mu]3-succinato-calcium(II)], [Ca(C4H5O4)]n, was synthesized by reaction of CaCl2 2H2O and succinic acid in an aqueous medium under hydrothermal microwave conditions. The structure contains infinite layers of edge-sharing calcium pentagonal-bipyramidal polyhedra forming six-membered rings connected through succinate ligands. Such an assembly of inorganic building units is unique for calcium metal-organic framework-type structures. Adjacent layers are packed into a final pseudo-three-dimensional structure through weak C-H...O hydrogen bonds
COBISS.SI-ID: 4875034