Conformational equilibrium in supramolecular chemistry: Dibutyltriuret case

Abstract

SummaryThe association of substituted benzoates and naphthyridine dianions was used to study the complexation of dibutyltriuret. The title molecule is the simplest molecule able to form two intramolecular hydrogen bonds. The naphthyridine salt was used to break two intramolecular hydrogen bonds at a time while with the use of substituted benzoates the systematic approach to study association was achieved. Both, titrations and variable temperature measurements shed the light on the importance of conformational equilibrium and its influence on association in solution. Moreover, the associates were observed by mass spectrometry. The DFT-based computations for complexes and single bond rotational barriers supports experimental data and helps understanding the properties of multiply hydrogen bonded complexes.

Conformational and Tautomeric Control by Supramolecular Approach in Ureido-N-iso-propyl,N’-4-(3-pyridin-2-one)pyrimidine

“…It is also worth mentioning that, for 1 and 1Me , the structural change (tautomerism) is crucial (keto vs. fixed enol form). During an additional experiment 1 was titrated with the use of tetrabutylammonium benzoate as before [29]. An existence of a multiple equilibrium is manifested[46] by the deviation of the titration curve from Benesi–Hildebrand equation for H10 and H11 with the largest Δδ = 0.40 (CIS) ppm being observed during titration for aromatic CH (H10, doublet) excluding the data form calculation of the association constant.…”

“…by interaction with designed hosts. Thus, the intramolecular hydrogen bond (IMHB) in heterocyclic urea derivatives can be broken by interaction with anions [29] or neutral molecules [4]. The break two intramolecular hydrogen bonds is also possible [30].…”

Thetrans/cisphotoisomerization in hydrogen bonded complexes with stability controlled by substituent effects: 3-(6-aminopyridin-3-yl)acrylate case study

“…The computationally obtained data related to the energy of intermolecular interaction, in general, follow the effect of the substituent in anion binding (both in trans and cis forms) as for previously studied derivatives. 5,6 Thus, it is reasonable to tell the same effects drive the association in the currently studied compounds. Moreover, the proton transfer reaction suggested by the experimental data is supported by the strength of the hydrogen bonds in 1+f À complex versus that in 2+f.…”

“…These molecules may be used in crystal engineering, as a selective sensor for nitro-compounds 4 and are able to form intramolecular hydrogen bond that is broken upon association. [5][6][7] Their main popularity in organic chemistry lies in organocatalytic properties of sulfur derivatives (thioureas). 8 The studies on complexation of ureas are quite popular especially in light of interactions of these molecules with oxoanions or carboxylates.…”

“…One of examples may be the bis(urea) that is, in theory, able to break two intramolecular hydrogen bonds upon association. 5,7 Thus, it is crucial to know the interaction of the simple supramolecular synthons. This, for sure, move the research towards more complex systems as it was realized for ternary ones.…”