Related Experiment Video
Updated: Jun 6, 2026
08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Real-time probing of ion pairing dynamics with 2DIR spectroscopy
Kwang-Hee Park1, Seung Ryul Choi, Jun-Ho Choi
1Department of Chemistry, Korea University, Seoul 136-701, Korea.
Summary
Ultrafast 2D Infrared spectroscopy reveals Li+ and SeCN- ion pairing dynamics in DMF. The LiSeCN contact ion pair dissociation time constant was determined to be 420±40 picoseconds.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Spectroscopy
Background:
- Ion pairing is crucial in chemical reactions and solution properties.
- Understanding ion pairing dynamics on ultrafast timescales is essential for controlling chemical processes.
- SeCN- serves as an effective vibrational probe due to its distinct spectral signature.
Purpose of the Study:
- To investigate the real-time dynamics of Li+ and SeCN- ion pairing in N,N-dimethyl formamide (DMF).
- To determine the dissociation time constant of the LiSeCN contact ion pair using advanced spectroscopic techniques.
Main Methods:
- Chemical exchange two-dimensional infrared (2D IR) spectroscopy was employed.
- SeCN- was used as a vibrational probe in DMF.
- Ultrafast spectroscopy allowed for real-time monitoring of spectral changes.
Main Results:
- The CN stretch frequency of the LiSeCN contact ion pair was significantly blue-shifted compared to free SeCN-.
- This spectral distinction enabled clear differentiation between free and paired ions.
- The dissociation time constant of the LiSeCN contact ion pair was measured to be 420±40 ps.
Conclusions:
- 2D IR spectroscopy is a powerful tool for studying ultrafast ion pairing dynamics.
- The determined dissociation time constant provides critical insight into the stability and kinetics of LiSeCN ion pairs in DMF.
- This research advances the understanding of ion solvation and interactions in polar aprotic solvents.
Related Concept Videos
01:12Two-Dimensional (2D) NMR: Overview
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
01:162D NMR: Overview of Homonuclear Correlation Techniques
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
COSY90 is the standard two-dimensional (2D) COSY experiment that...
01:12Double Resonance Techniques: Overview
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
01:182D NMR: Overview of Heteronuclear Correlation Techniques
Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.
01:21Tandem Mass Spectrometry
Tandem mass spectrometry is a technique that uses multiple mass analyzers in series to obtain a higher selectivity and reduce chemical noise during analyte detection. Instruments with multiple analyzers separated by an interaction cell enable secondary fragmentation and selected study of the fragment ions.Secondary fragmentations occur in the interaction cell and can be induced by various factors. Fragmentation induced by collision with inert gases, such as N2, Ar, He, etc., is called...
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...