Thermal and spectroscopic study of zinc, manganese, copper, cobalt and nickel 2,3-pyrazinedicarboxylate

In the frame of this work complexes of selected 3d transition metals with 2,3-pyrazinedicarboxylic acid were synthesized and characterized by spectroscopic (IR, Raman) and thermal (TGA, DSC) methods. FT-IR and FT-Raman spectra of 3d metal 2,3-pyrazinedicarboxylates were recorded and analyzed in the region of 4000–400 cm−1. The structures of the three 2,3-pyridazinecarboxylic acid conformers were calculated using density functional (DFT) hybrid method B3LYP with non-local correlation provided by Lee–Young–Parr expression. All calculations were carried out with functional base 6–311++G(d,p) in Gaussian 09 package. The aromaticity indices HOMA and I6 (Bird) for diffraction structures of 2,3-pyrazinedicarboxylates and the theoretical structures of the acid conformers were calculated. Thermal properties of the complexes were studied in the temperature range of 30–900 °C. Measurements were carried out in the atmosphere of oxygen and argon. The products of dehydration and decomposition processes were determined based on TG and DSC curves. Thermal studies revealed that 2,3-pyrazinedicarboxylic acid complexes are hydrated, and upon heating decompose to metal oxides.