Constructing two 1D coordination polymers and one mononuclear complex by pyrazine- and pyridinedicarboxylic acids under mild and sonochemical conditions: magnetic and CSD studies

In this work, we report the synthesis and crystal structure of two 1D coordination polymers and one mononuclear complex based on pyrazine-2,3-dicarboxylic acid (H(2)pyz-2,3-dc), pyridine-2,3-dicarboxylic acid (H(2)py-2,3-dc) and pyridine-2,6-dicarboxylic acid (H(2)py-2,6-dc) ligands, namely {[2-Hatz](2)[Cu[pyz-2,3-dc)(2)]}(n) (2-atz = 2-aminothiazole) (1), {[2-Hatz](2)[Cu(py-2,3-dc)(2)]}(n) (2) and [Cu(py-2,6-dc)(2-atz)(H2O)] (3). Single crystal X-ray diffraction analyses showed that utilizing different structural isomers (2,3-and 2,6-) of dicarboxylic acid led to geometrical and structural diversity. Two coordination polymers have a distorted octahedral geometry, in which the (pyz-2,3-dc)(2-) and (py-2,3-dc)(2-) moieties act as tridentate bridging ligands in 1 and 2 so that 1D chains are in a similar fashion, while complex 3 exhibits a 3D supramolecular network with a square pyramidal geometry. Moreover, to investigate the influence of particle size on physical properties such as magnetic behavior and thermal stability, nanostructures of the mentioned polymers were synthesized by a sonochemical method and characterized by scanning electron microscopy (SEM), elemental analyses, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), and thermogravimetric (TGA) analyses. Investigation of the magnetic properties of compounds 1, 2 and the corresponding nanostructures indicates that there are weak antiferromagnetic interactions between the Cu-II ions in the temperature range of 1.8-300 K.