Intra- versus Intermolecular Hydrogen Bonding: Solvent-Dependent Conformational Preferences of a Common Supramolecular Binding Motif from (HNMR)-H-1 and Vibrational Circular Dichroism Spectra

Author(s)

Demarque, Daniel P. ^{[1, 2]} ; Merten, Christian ^[1]

Affiliation

^[1] Ruhr Univ Bochum, Lehrstuhl Organ Chem 2, Univ Str 150, D-44801 Bochum - Germany

^[2] Univ Sao Paulo, Fac Ciencias Farmaceut Ribeirao Preto, Nucl Pesquisa Prod Nat & Sintet, Dept Fis & Quim, Sao Paulo - Brazil

• Document type: Journal article
• Source: CHEMISTRY-A EUROPEAN JOURNAL; v. 23, n. 71, p. 17915-17922, DEC 19 2017.
• Web of Science Citations: 7

Abstract

When predicting binding properties of small molecules or larger supramolecular aggregates, intra- and intermolecular hydrogen bonds are often considered the most important factor. Spectroscopic techniques such as (HNMR)-H-1 spectroscopy are typically utilized to characterize such binding events, but interpretation is often qualitative and follows chemical intuition. In this study, we compare the effects of intramolecular hydrogen bonding and solvation on two chiral 2,6-pyridinediyl-dialkylamides. In comparison with (HNMR)-H-1 spectroscopy, vibrational circular dichroism (VCD) spectroscopy proved to be more sensitive to conformational changes. In fact, the change of the solvent from CDCl3 to {[}D-6]DMSO generates mirror-image VCD spectra for the same enantiomer. Here, the common sense that the sterically less hindered group is more prone to solvation proved to be wrong according predicted VCD spectra, which clearly show that both asymmetric amide hydrogens are equally likely to be solvated, but never simultaneously. The competition between intra- and intermolecular hydrogen bonding and their importance for a correct prediction of spectral properties are discussed. (AU)

• FAPESP's process: 14/18052-0 - Tissue localization of tannins and Anthraquinones acting on gastrointestinal system
• Grantee: Daniel Pecoraro Demarque
• Support Opportunities: Scholarships in Brazil - Doctorate