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Issue 19, 2017
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Substituent effects on the basicity (pKa) of aryl guanidines and 2-(arylimino)imidazolidines: correlations of pH-metric and UV-metric values with predictions from gas-phase ab initio bond lengths

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Abstract

The dissociation constants of two related series of 2-(arylimino)imidazolidine and aryl guanidine α2-adrenoceptor antagonists (35 compounds in total) were measured by potentiometric titrations and by UV-spectrophotometry using the 96-well microtitre plate method. The experimental values obtained using both methods were quite consistent and showed a very good agreement with the pKa values calculated using the AIBLHiCoS methodology, which uses only a single bond length obtained using ab initio calculations at a low level of theory. The prediction power of the imidazolidine and guanidine set of compounds was very good with deviations typically <0.30 and <0.24 pKa units, and a mean absolute error (MAE) of 0.23 and 0.29, respectively. The study of the quantitative effect of diverse substituents on the basicity of aryl guanidine and 2-(arylimino)imidazolidine derivatives is useful for medicinal chemists working with biologically relevant guanidine-containing molecules.

Graphical abstract: Substituent effects on the basicity (pKa) of aryl guanidines and 2-(arylimino)imidazolidines: correlations of pH-metric and UV-metric values with predictions from gas-phase ab initio bond lengths

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Publication details

The article was received on 10 Jul 2017, accepted on 28 Jul 2017 and first published on 30 Aug 2017


Article type: Paper
DOI: 10.1039/C7NJ02497E
Citation: New J. Chem., 2017,41, 11016-11028
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    Substituent effects on the basicity (pKa) of aryl guanidines and 2-(arylimino)imidazolidines: correlations of pH-metric and UV-metric values with predictions from gas-phase ab initio bond lengths

    C. Dardonville, B. A. Caine, M. Navarro de la Fuente, G. Martín Herranz, B. Corrales Mariblanca and P. L. A. Popelier, New J. Chem., 2017, 41, 11016
    DOI: 10.1039/C7NJ02497E

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