Solid and solution states studies of two Mn(II) complexes based on N-oxidized pyridine-2,5-dicarboxylic acid

Two coordination complexes, [Mn-2(pydco)(2)(phen)(2)(H2O)(2)]center dot 2H(2)O (1) and [Mn(3-pyco)(2)(H2O)(4)] (2), based on Mn(II), pyridine-2,5-dicarboxylic acid N-oxide (H(2)pydco), and 1,10-phenanthroline (phen) as organic ligands have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X-ray diffraction. We have synthesized the first Mn(II) complex of H(2)pydco. Interestingly, in situ hydrothermal decarboxylation occurred in 2 and (pydco)(2-) was totally transformed into pyridine-3-carboxylate N-oxide (3-pyco)(-) under hydrothermal conditions. The complexation reactions of these molecules with Mn2+ ions were investigated by means of solution studies. The stoichiometry of the most abundant species in the solution (prior to the pH at which precipitation occurs) was very close to that of the corresponding crystalline solid-state complexes.