Abstract
Four novel hetero dimetallic mixed metal complexes of 2,6-pyridinedicarboxylic acid (H2dipic), [Ni(H2O)5Co(dipic)2] (1), [Co(H2O)5Co(dipic)2][Ni(H2O)5Ni(dipic)2][Co(dipic)(H2O)3] (2), [Cu(H2O)5Ni(dipic)2]2[Co(dipic)(H2O)] (3) and [Ni(H2O)5Cu(dipic)2]2[Co(dipic)(H2O)] (4) have been prepared and characterized by elemental, AAS, spectral (IR and UV-Vis), and thermal analyses, as well as by using magnetic measurement and molar conductivity techniques. The results indicate that metal ions coordinate with 2,6-pyridinedicarboxylate ions (dipic2-) nitrogen atoms and carboxylate oxygen atoms of ligands. The mole ratio of dipic2- and metal ions in the complexes have been determined to be 2:2 (Co, Ni) for 1, 5:5 (3Co, 2Ni) for 2, 5:5 (Co, 2Ni and 2Cu) for 3 and 5:5 (Co, 2Ni and 2Cu) for 4 according to the results of elemental analysis. The structures of 1-4 might be proposed as octahedral ([Cu(dipic)(H2O)] unit for 2 square plane) according to results of spectroscopic analysis. The TG and DTA properties of compounds have been studied.
 
 KEY WORDS: 2,6-Pyridinedicarboxylic acid, Mixed metal, Metal complex
 
 Bull. Chem. Soc. Ethiop. 2020, 34(2), 313-321
 DOI: https://dx.doi.org/10.4314/bcse.v34i2.9
Highlights
The metal complexes for pyridine-2,6-dicarboxylic acid and its deprotonated forms (Hdipic- and dipic2-) show interesting structural features with various coordination modes [1], stabilization of unusual oxidation states [2] and insulin-mimetic effects [3, 4]
A single planar DPC ligand associates in the equatorial plane of a metal cation with other ligands such as, H2O or pyridine-based heterocycles [4, 5], which occupy the remaining sites. This leads to the formation of square pyramidal [4, 6,7,8,9,10] or octahedral coordination geometry [4, 10,11,12, 14]
The structures of 1-4 might be proposed as octahedral ([Cu(dipic)(H2O)] unit for 2 square plane) according to results of elemental, spectral, thermal analyses, magnetic measurement and molar conductivity
Summary
The metal complexes for pyridine-2,6-dicarboxylic acid (or dipicolinic acid, H2dipic) and its deprotonated forms (Hdipic- and dipic2-) show interesting structural features with various coordination modes [1], stabilization of unusual oxidation states [2] and insulin-mimetic effects [3, 4]. Four novel hetero dimetallic mixed metal complexes of 2,6-pyridinedicarboxylic acid (H2dipic), [Ni(H2O)5Co(dipic)2] (1), [Co(H2O)5Co(dipic)2][Ni(H2O)5Ni(dipic)2][Co(dipic)(H2O)3] (2), [Cu(H2O)5Ni(dipic)2]2[Co(dipic)(H2O)] (3) and [Ni(H2O)5Cu(dipic)2]2[Co(dipic)(H2O)] (4) have been prepared and characterized by elemental, AAS, spectral (IR and UV-Vis), and thermal analyses, as well as by using magnetic measurement and molar conductivity techniques. The mole ratio of dipic2- and metal ions in the complexes have been determined to be 2:2 (Co, Ni) for 1, 5:5 (3Co, 2Ni) for 2, 5:5 (Co, 2Ni and 2Cu) for 3 and 5:5 (Co, 2Ni and 2Cu) for 4 according to the results of elemental analysis.
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