Synthesis and characterization of six copper(II) and cobalt(II) octahedral complexes [M(6-OHpic)
2(H
2O)
2] (6-OHpic is 6-hydroxypicolinato), [M(2-OHnic)
2(H
2O)
2] (2-OHnic is 2-hydroxynicotinato), [Cu(6-OHnic)
2(H
2O)
2] (6-OHnic is 6-hydroxynicotinato) as well as [Co(H
2O)
6](6-OHnic)
2 are reported. Their characterization was carried out using elemental analysis, infrared, and magnetic measurements. Based
on IR spectra,
N,O-coordination of 6-OHpic (via the oxygen atom of the carboxyl group and the nitrogen atom of the pyridine ring),
O,O-asymmetrically chelating coordination of the carboxyl groups as well as ionic coordination of 6-OHnic and chelating
O,O-coordination (through the oxygen atom of the carboxyl group and the oxygen atom of the amide group) of keto(amide) tautomer
of 2-OHnic were supposed. Moreover, crystal structures of 2-OHnicH and the complex [Co(2-OHnic)
2(H
2O)
2]) were determined by X-ray single crystal structure analysis. The system of hydrogen bonds predominantly stabilizes the keto(amide)
tautomer of both 2-hydroxynicotinic acid and 2-OHnic anion in the cobalt(II) complex. Intermolecular hydrogen bonds (between
the oxygen atom of the amide group and the hydrogen atom of the NH group) interconnect two neighbouring molecules of 2-OHnicH
forming dimers. Cobalt(II) in complex [Co(2-OHnic)
2(H
2O)
2] has nearly a regular compressed tetragonal bipyramidal arrangement.
Presented at the 1st International Conference “Applied Natural Sciences” on the occasion of the 10th anniversary of the University
of Ss. Cyril and Methodius, Trnava, 7–9 November 2007.
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