Novel coordination compounds of alkaline earth metals with coumarilic acid. Synthesis and characterization

Abstract

In this study, novel coordination compounds of coumarilic acid with 2A group alkaline earth metal cations [Mg2+ (1), Ca2+ (2), Sr2+ (3) and Ba2+(4)] were synthesized and structural characterized. The structural properties of the new molecules obtained were studied by melting point, elemental analysis, infrared spectroscopy, single crystal x-ray diffraction (SC-XRD), powder x-ray diffraction (P-XRD) spectroscopy. In addition, the thermal stability of the compounds were examined by thermal analysis (TGA/DTA) curves in an inert nitrogen atmosphere. When the structural properties of the molecules were examined, it was seen that the structure numbered 1 {[Mg(H2O)6].2(C9H5O3)} differed from the others and it was a kind of aqua complex. The coumarilate anions anionically located outside the coordination sphere serve as the counter-ion of the molecule. It has been determined that the other structures 2 {?-(H2O)2[Ca(C9H5O3)(H2O)3]2.2(C9H5O3)}, 3 {?-(H2O)3[Sr(C9H5O3)(H2O)2]2.2(C9H5O3)} and 4 {?-(H2O)3[Ba(C9H5O3)(H2O)2]2.2(C9H5O3)} are in polymeric form and the coordination number of metals are eight. According to the spectroscopic analysis, these three structures are thought to be in isostructure form. It has been determined that in the unit cell in the structure 3 whose single crystal structure has been resolved, aqua and coumarilate ligands of two metal cations are connected to each other in the bridge position and coordination is ensured with aqua and bidentate anionic coumarilate ligands located in the terminal position. At the end of thermal decomposition, it was determined that relevant metal oxide residues remained in all structures and this situation was defined by powder XRD. © 2021