Ultrasound irradiation effect on morphology and size of two new potassium coordination supramolecule compounds

Two new potassium coordination supramolecular compounds (2D and 1D), [K(H₃L)(H₂L)(H₂O)]_n·H₂O (1) and [K(H₂L')(HL')(H₂O)₂]·H₂O (2), (L=1,3,5-tricarboxylic acid, L'=2,6-pyridinedicarboxylic acid), have been synthesized under different experimental conditions. Micrometric crystals (bulk) or nano-sized materials have been obtained depending on using the branch tube method or sonochemical irradiation. All materials have been characterized by field emission scanning electron microscopy (FE-SEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), FT-IR spectroscopy and elemental analyses. Single crystal X-ray analyses on compounds 1 and 2 show that K⁺ ions are 3- and 7-coordinated, respectively. Additionally, H-bonds incorporate the layers and chains in 1 and 2 into 3D and 2D (along (0,0,1) direction) frameworks. Topological analysis shows that the compound 1 and 2 are 3,6-coordinated kgd and 2,4-coordinated 2,4C4 net. The thermal stability of compounds 1 and 2 in bulk and nano-size has been studied by thermal gravimetric (TG) and differential thermal analyses (DTA) and compared each other. The role of different parameters like temperature, reaction time and ultrasound irradiation power on the growth and morphology of the nano-structures are studied. Results suggest that an increase of temperature, sonication power and reduction of reaction time led to a particle size decrease.