Synthesis and Characterization of Transition Metal Complex Cation Heptaborate Structures

Heptaborate structures with transition metal complex cations were synthesized and characterized using elemental analysis, melting point determination, FT-IR, TGA/DTA analysis, UV analysis, x-ray diffraction (XRD) analysis methods. In the infrared spectra of heptaborate salt structures, peaks of (-M-N)phen and (-M-N)pyrd stretching vibrations, which indicate the presence of transition metal complex, were observed. As the characteristic vibrations of the heptaborate structure, the -OH peaks of the B-OH bonds present in the structures and the asymmetric and symmetrical stretching vibrations, which confirm the presence of four trigonal borate molecules in the structures, appeared as sharp peaks. It was observed that the thermal analysis decomposition curves of heptaborate salt structures with transition metal complex cations were similar. Depending on the similar degradation characteristics of the molecules, it is seen that the hydrate waters settled outside the coordination sphere in all structures move away from the structures in a single step. As the second degradation step of heptaborate salt structures, the removal of water in amounts that can be attributed to the removal of -OH groups in the borate rings in the form of water vapor in all structures was detected. It was seen that this degradation step took place in a single step in all structures and the related experimental theoretical mass losses were compatible with each other. Combustion degradation of organic ligands was observed as the final degradation step of heptaborate salt structures with metal cation complexes. While peaks belonging to heptaborate rings were observed from the recorded powder x-ray diffraction patterns, electronic transition data also supported that the metal cation complex was in octahedral geometry.