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Interconverting Hydrogen-Bonding and Weak n → π* Interactions in Aqueous Solution: A Direct Spectroscopic Evidence
Pranab Deb1,2, Geun Young Jin3,4, Santosh K Singh5
1Physical and Materials Chemistry Division , CSIR-National Chemical Laboratory (CSIR-NCL) , Dr. Homi Bhabha Road , Pune 411008 , India.
The Journal of Physical Chemistry Letters
|August 29, 2018
Summary
Researchers used 2D infrared spectroscopy to observe weak noncovalent interactions, like hydrogen bonds and n → π* interactions, in water. They found these interactions rapidly interconvert, with kinetics accelerating in higher water concentrations.
Area of Science:
- Chemical Physics
- Molecular Biophysics
- Spectroscopy
Background:
- Noncovalent interactions are crucial for molecular structure and function.
- Studying weak, transient interactions in solution is experimentally challenging.
- Existing methods rely on indirect data and theory, often missing solvent effects.
Purpose of the Study:
- To experimentally investigate the coexistence and interconversion of strong and weak noncovalent interactions in aqueous solution.
- To probe the dynamics of these interactions using advanced spectroscopic techniques.
- To provide new insights into the behavior of weak interactions in biologically relevant environments.
Main Methods:
- Utilized two-dimensional infrared (2D IR) spectroscopy.
- Analyzed spectral dynamics to identify and track distinct noncovalent interactions.
- Varied water content to observe effects on interaction kinetics.
Main Results:
- Demonstrated the simultaneous presence of strong hydrogen bonds and weak n → π* interactions in water.
- Observed that these interactions dynamically interconvert.
- Found that the rate of interconversion increases with higher water concentrations.
Conclusions:
- Weak noncovalent interactions, such as n → π* interactions, are present and dynamic in aqueous solutions.
- Solvent fluctuations play a significant role in the behavior of these interactions.
- 2D IR spectroscopy offers a powerful tool for studying transient molecular interactions in solution.
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