Issue 38, 2009

NMR and DFT study on media effects on proton transfer in hydrogen bonding: concept of molecular probe with an application to ionic and super-polar liquids

Abstract

Media effects of ionic and super-polar liquids on the state of H-bonding were studied by NMR and DFT methods. The proton sharing (positioning) in the H-bond was monitored following the chemical shifts of picolinic acid N-oxide (PANO) used as the molecular probe. The relationships between PANO1H and 13C chemical shifts and proton position in the O–H⋯O bridge were calibrated using traditional organic solvents and other H-bond complexes of pyridine N-oxide with acids to increase the H-bond strength. A reliable parameter for H-bond monitoring was proposed. The state of the H-bond in ionic liquid media is largely governed by the dielectric properties of the bulk media. A drastic fall-out of PANO/[BuMePyr][TfO] from the general dielectric scheme built using solvents with increasing dielectric constant (from chloroform to water and culminating with formamide) was observed. On a molecular level this effect indicates that the ionic liquid [BuMePyr][TfO] can act on H-bonded systems as a stimulant of proton transfer. In ‘super-polar’ media (formamide) the intramolecular H-bond system converts into an intermolecular one forming a neutral H-bond complex of PANO with the formamide molecule.

Graphical abstract: NMR and DFT study on media effects on proton transfer in hydrogen bonding: concept of molecular probe with an application to ionic and super-polar liquids

Article information

Article type
Paper
Submitted
05 Nov 2008
Accepted
16 Jun 2009
First published
27 Jul 2009

Phys. Chem. Chem. Phys., 2009,11, 8592-8600

NMR and DFT study on media effects on proton transfer in hydrogen bonding: concept of molecular probe with an application to ionic and super-polar liquids

V. Balevicius, Z. Gdaniec and K. Aidas, Phys. Chem. Chem. Phys., 2009, 11, 8592 DOI: 10.1039/B819666D

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