F. Peral et E. Gallego, A study by ultraviolet spectroscopy on self-association of purine, 6-methylpurine, benzimidazole, and imidazo [1,2-a]pyridine in aqueous solution, SPECT ACT A, 56(4), 2000, pp. 747-759
Citations number
29
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences
Journal title
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
The self-association of four heteroaromatic compounds with fused five- and
six-membered rings: purine, 6-methylpurine, benzimidazole, and imidazo[1,2-
a]pyridine, was studied in aqueous solution at different pH values, by ultr
aviolet spectroscopy. The variation in molar absorptivity with the concentr
ation of these compounds was measured for the band systems in the mid-ultra
violet region. Hypochromic deviations from the Beer-Lambert law with increa
sing concentration were found for all compounds. These results were interpr
eted in terms of self-association processes involving the formation of dime
rs and, in certain cases, also the formation of polymers. From the fitting
of the experimental curves of hypochromic effects, self-association constan
ts for dimerization and polymerization were calculated. The results obtaine
d are discussed in relation to the self-association properties of the build
ing blocks of each compound, studied by us in previous works. The relevance
of the position of the nitrogen atoms at the five- and six-membered rings
was analyzed to elucidate the nature of the self-association processes, in
particular the tendency to polymerization. The values of the calculated sel
f-association constants are discussed in relation to the intermolecular int
eraction energies of these compounds in aqueous solution. (C) 2000 Elsevier
Science B.V. All rights reserved.