F. Peral et E. Gallego, Self-association of pyridine-2,6-dicarboxylic acid in aqueous solution as determined from ultraviolet hypochromic and hyperchromic effects, SPECT ACT A, 56(11), 2000, pp. 2149-2155
Citations number
15
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences
Journal title
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
The self-association of pyridine-2,6-dicarboxylic acid (dipicolinic acid),
was studied in aqueous solution at the pH values of 0.2, 3.5, 6.9 and 13.0,
by ultraviolet spectroscopy. The variation in molar absorptivity with the
concentration of this compound was measured for the band in the mid-ultravi
olet region. Deviations from Beer-Lambert law with increasing concentration
were found at the pH values of 0.2, 3.5 and 6.9. Hypochromic effects were
detected at pH 0.2 and 6.9, while a hyperchromic effect was observed at pH
3.5. These results were interpreted in terms of self-association leading to
the formation of dimers. From the fitting of the experimental curves of hy
pochromic or hyperchromic effects, self-association constants were calculat
ed. The occurrence of hypochromic and hyperchromic effects was analyzed in
terms of vertical and horizontal interactions, respectively, to elucidate t
he nature of the self-association processes, stacking or hydrogen bonding,
relevant to each of the protolytic species of dipicolinic acid in aqueous s
olution. (C) 2000 Elsevier Science B.V. All rights reserved.