Related Experiment Video
Updated: Oct 1, 2025
05:51
Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
6.3K
Excited-state proton transfer in a 2-aminopyridine dimer: a surface hopping study
1Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India. jyotirmoyray@iisc.ac.in.
Physical Chemistry Chemical Physics : PCCP
|March 9, 2022
Summary
Excited-state intermolecular proton transfer in 2-aminopyridine dimers occurs ultrafast, around 100 fs. This process involves charge transfer (CT) states and is facilitated by locally excited (LE)/CT state intersections.
Area of Science:
- Physical Chemistry
- Theoretical Chemistry
- Spectroscopy
Background:
- The 2-aminopyridine dimer exhibits doubly hydrogen bonded interactions.
- Previous studies suggest ultrafast proton transfer (50 fs) involving charge transfer (CT) states.
Purpose of the Study:
- To theoretically investigate the excited-state intermolecular proton transfer in a 2-aminopyridine dimer.
- To elucidate the role of locally excited (LE) and charge transfer (CT) states in the proton transfer dynamics.
Main Methods:
- Trajectory-based surface hopping simulations.
- Calculations performed at the XMS-CASPT2 and TDDFT levels of theory.
- Analysis of intersections between LE and CT states.
Main Results:
- Proton transfer occurs on an ultrafast timescale (approx. 100 fs) via charge transfer (CT) states.
- Locally excited (LE) states do not facilitate proton transfer.
- Excitation of the NH stretch can promote CT state-driven proton transfer.
Conclusions:
- The excited-state proton transfer in 2-aminopyridine dimers is primarily driven by charge transfer (CT) states.
- Access to LE/CT intersection regions is crucial for proton transfer.
- Non-adiabatic transitions enable return to the ground state.
More Related Videos
Related Concept Videos
01:13¹H NMR: Complex Splitting
1.4K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
1.4K
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
940
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...
940
01:10Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule
1.5K
In the AX proton spin system, proton A can sense the two spin states of a coupled proton X, resulting in a doublet NMR signal with two peaks of equal (1:1) intensity. When proton A is coupled to two equivalent protons (AX2 spin system), the spin states of each X can be aligned with or against the external field, creating three possible scenarios. This results in a 1:2:1 triplet signal, where the central peak corresponds to the chemical shift of A and is twice as large or intense as the...
1.5K
01:12Double Resonance Techniques: Overview
328
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...
328
01:19NMR Spectroscopy Of Amines
9.5K
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...
9.5K
01:162D NMR: Overview of Homonuclear Correlation Techniques
317
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...
317