Thermal behavior of manganese(II) complexes with pyridine-2,3-dicarboxylic acid

In this study, we analyzed influence of the type of the syntheses used: hydrothermal and non-hydrothermal on pyridine-2,3-dicarboxylic acid (2,3pydcH 2 ) coordina- tion fashion. Two manganese(II) complexes: [Mn(H 2 O) 3 (2,3pydc)] n ( 1 ) and [Mn(H 2 O) 6 ][Mn(2,3pydcH) 3 ] 2 ( 2 ) were successfully synthesized from the non-hydrothermal reac- tion system containing organic ligand and different Mn(II) salts. The received complexes have been prepared and characterized by spectroscopic (IR, Raman), structural (X-ray single crystal), and thermogravimetric methods. The results of the crystal study give some evidence that ligand exhibits various topological structures and interest- ing properties. Pyridine-2,3-dicarboxylic acid acts as monodicarboxylate N,O-chelating anion (complex 2 )ora doubly deprotonated three-dentate- N , O , O 0 dicarboxylate ion (complex 1 ). In the [Mn(H 2 O) 6 ][Mn(2,3pydcH) 3 ] 2 the coordination geometry around Mn(1) ion can be considered as being distorted octahedron {MnN 3 O 3 }. The Mn(2) cat- ion possesses the same coordination polyhedron (octahe- dral). We have also analyzed influence of furnace atmosphere on the thermal behavior and the kind of final product. The sample of ( 1 ) decomposes in four stages in N 2 (368–1073 K) and the final residue is MnO 2 . The ther- mogram of ( 2 ) exhibits three main distinct decomposition steps (383–973 K). A residue of MnO is remained. In both air and nitrogen atmosphere, Mn(II) complexes ( 1 ) and ( 2 ) keep unchanged over all steps of decomposition. Only the final residues are different (Mn 2 O 3 are formed). The course of pyrolysis and molecular structure of the complexes lead to the same conclusion about the strength of metal–ligand bonds. On the basis of the above results, it is concluded that the thermal stability of the manganese(II) compounds is slightly different