Related Experiment Video
Updated: Jul 8, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Ion-pair interaction in pyridinium carboxylate solutions
Erik R Berg1, Daniel D Green, Diane C Moliva
1Department of Physics, Concordia College, Moorhead, Minnesota 56562, USA.
Noisy light based coherent anti-Stokes Raman scattering (I(2)CARS) reveals how ion-pair interactions affect molecular vibrations. Pyridinium and carboxylate ion-pair formation causes distinct frequency shifts in pyridine and pyridinium ring breathing modes.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Chemical Physics
Background:
- Ion-pair interactions are crucial in chemical reactions and material properties.
- Understanding these interactions requires sensitive molecular probes.
- Coherent anti-Stokes Raman scattering (CARS) offers vibrational information but can be limited by signal strength.
Purpose of the Study:
- To investigate ion-pair interactions between pyridinium cations and carboxylate anions.
- To utilize noisy light based coherent anti-Stokes Raman scattering (I(2)CARS) for enhanced sensitivity.
- To analyze the vibrational frequency shifts associated with these interactions.
Main Methods:
- Preparation of binary mixtures of pyridine with various carboxylic acids.
- Utilizing noisy light based coherent anti-Stokes Raman scattering (I(2)CARS) spectroscopy.
- Analysis of frequency shifts in the ring breathing modes of pyridine and pyridinium.
Main Results:
- Brønsted acid-base reactions formed pyridinium and carboxylate ions.
- Pyridine and pyridinium exhibit strong I(2)CARS signals from their ring breathing modes.
- Hydrogen bonding blue-shifted pyridine's mode; ion-pairing red-shifted pyridinium's mode.
Conclusions:
- I(2)CARS is effective for studying ion-pair interactions in solution.
- Vibrational frequency shifts provide insights into electronic behavior during ion-pairing.
- The study establishes a link between molecular structure, interactions, and spectroscopic signatures.
More Related Videos
06:44From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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
Related Concept Videos
Ionic Association
Molecular Shape and Polarity
Basicity of Heterocyclic Aromatic Amines
Acid Halides to Carboxylic Acids: Hydrolysis
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
Intermolecular Forces
VSEPR Theory and the Effect of Lone Pairs