Related Experiment Video
Updated: Aug 6, 2026
10:28
Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy
Published on: May 27, 2018
Local Interactions and Dynamics in Aqueous Imidazole Probed by Vibrational and NMR Spectroscopy
Nicole Abdou1, Eva Dahlqvist1, Anna Martinelli1
1Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96Gothenburg, Sweden.
The Journal of Physical Chemistry. B
|July 20, 2026
Summary
Aqueous imidazole solutions were studied using spectroscopy. A 1:1 water/imidazole ratio disrupts imidazole
Area of Science:
- Chemistry
- Materials Science
- Biophysics
Background:
- Imidazole is a fundamental molecule in biology, chemistry, and technology.
- Aqueous imidazole solutions are unique liquid systems with complex hydrogen bonding networks.
- Understanding their structure is crucial for applications in proton-conducting materials and beyond.
Purpose of the Study:
- To investigate the local structure and molecular dynamics of aqueous imidazole solutions.
- To determine how water affects the hydrogen bonding network and structure of imidazole.
- To complement existing knowledge and differentiate between computational models.
Main Methods:
- Utilized multiple experimental techniques, primarily vibrational (Raman) and Nuclear Magnetic Resonance (NMR) spectroscopy.
- Studied aqueous imidazole solutions across a range of imidazole mole fractions (0 to 1).
- Performed detailed peak fit analysis on spectral data.
Main Results:
- Distinct changes in Raman spectra indicate that a 1:1 water/imidazole ratio is a critical point where imidazole solvation begins, disrupting its crystalline structure.
- Further dilution in water causes only marginal changes to the local structure.
- Experimental findings support computational models suggesting a prevalence of hydrogen-bonded imidazole chains over other dimer forms.
Conclusions:
- The 1:1 water/imidazole ratio is a key threshold for structural changes in aqueous imidazole.
- Imidazole's local structure is significantly altered upon solvation in water.
- The study provides experimental evidence favoring specific computational models of imidazole aggregation in aqueous solutions.
More Related Videos
08:54Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
Published on: January 25, 2020
08:49Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy
Published on: December 1, 2023
Related Concept Videos
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
01:24IR Spectroscopy: Molecular Vibration Overview
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
01:25Basicity of Heterocyclic Aromatic Amines
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
01:19NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...