Novel mixed ligand complexes of alkaline earth metals with coumarilic acid and nicotinamide

Abstract

Coordination compounds with mixed ligands were synthesized with 2A group (Mg2+, Ca2+, Ba2+, Sr2+) alkaline earth metal cations of coumarilic acid and nicotinamide ligands. Afterward, the structural properties of these new molecules were investigated by melting point, elemental analysis, infrared spectroscopy, thermal analysis (TGA / DTA) curves, powder X-ray diffraction (P-XRD) spectroscopy. It has been suggested that the complex structure with the Mg2+ metal center is different from the other three structures. In this structure, it was determined that four aqua and two nicotinamide ligands were located in the coordination sphere, and the coordination number was six, as expected. With two monoanionic coumarilic acids located outside the coordination sphere, complex charge equivalence was achieved. The other three molecules, Sr2+ and Ba2+, have iso-structural properties, and it is suggested that both structures contain a dinuclear metal center, and two aqua ligands are located in the bridging position between metal centers. Besides, the two coumarilate ligands involved in coordination are thought to coordinate with the primary metal cation through carbonyl and acidic oxygens while coordinating with the secondary metal cation through furan oxygen, providing the third bridge connection between metal centers. Metal cations with nine coordination numbers complete the coordination sphere with two terminal aqua and one nicotinamide ligands, each included in the structure. In the molecule with Ca2+ cation, which differs little from these metal cation structures, the difference according to these structures can be interpreted as the coordination of furan oxygen with the secondary metal center due to the octet coordination of the Ca2+ cation. From the thermal analysis curves, it was determined that only the Mg2+ cation complex contained hydrate. As a result of thermal decomposition, it was determined that relevant metal oxide residues remained in all structures, and this situation was defined by powder XRD. © 2021, Turkish Chemical Society. All rights reserved.