Synthesis, spectroscopic, thermal and structural properties of metal-malonate complexes

In this work, (2-Meim)2[Co(mal)2(H2O)2] (1), (2-Meim)2[Ni(mal)2(H2O)2] (2), (4-Meim)2[Cu(mal)2] (3) and (2-Meim)2[Zn(mal)2(H2O)2] (4) complexes were synthesized by using malonic acid, 2-methylimidazole (2-Meim) and 4-methylimidazole (4-Meim). Composition of complexes were determined by elemental analysis. Spectroscopic (IR and UV-Vis.), magnetic and thermal properties of complexes were investigated. 1, 3 and 4 complexes were characterized by X-ray single crystal diffraction method. At room temperature spin only magnetic moments were calculated from the magnetic susceptibility measurement of complexes. Co(II), Ni(II) and Cu(II) complexes were found to be paramagnetic whereas Zn(II) complex was diamagnetic. Thermal decomposition behaviour of complexes were investigated by TG, DTG and DTA techniques. Thermal analysis datas show that complexes lose imidazole and aqua ligands in the first stage of decomposition and in the following stages mal ligands decompose to metaloxides. In the complexes, the malonate acted as dianionic bidentate ligand bonded to the metals and imidazole ligands were counterions. Coordination geometry of central atoms in the (2-Meim)2[Co(mal)2(H2O)2] and (2-Meim)2[Zn(mal)2(H2O)2] complexes were distorted octahedral, in the (4-Meim)2[Cu(mal)2]complex was square planar.