Tuning the hydrogen-bonding strength in 2,6-bis(cycloalkylcarbonylamino)pyridine assemblies by variable flexibility. Association constants measured by hydrogen-bonded vs. non-hydrogen-bonded protons

Author： Ośmiałowski Borys

Publisher： Taylor & Francis Ltd

ISSN： 1061-0278

Source： Supramolecular Chemistry, Vol.23, Iss.8, 2011-08, pp. : 579-586

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Abstract

The association of 2,6-bis(cycloalkylcarbonylamino)pyridines with rigid and non-rigid counterparts in chloroform solution was studied using ¹H NMR and computational methods. The angles within the cycloalkyl ring and the rotation of these substituents determine the strength of the association via triple hydrogen bonding. The dimerisation and methyl-methyl repulsion have been addressed as mechanisms restricting heterocomplexation of diacetamide. The association constants obtained by the shift changes of hydrogen-bonded protons are in agreement with those of methine protons. This `dual shift' method was proposed as an additional verification of association constants obtained generally by amino protons.