Related Experiment Video
Updated: Jun 5, 2025
05:51
Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
6.2K
Complementing Adiabatic and Nonadiabatic Methods To Understand Internal Conversion Dynamics in Porphyrin Derivatives
Pavel S Rukin1, Mariagrazia Fortino2, Deborah Prezzi1
1Istituto Nanoscienze - CNR, via Campi 213/A, 41125 Modena, Italy.
Journal of Chemical Theory and Computation
|December 11, 2024
Summary
Internal conversion in porphyrins differs due to molecular structure. This study reveals key vibrational modes driving excited-state population transfer, offering insights into photophysical dynamics.
Area of Science:
- Photochemistry
- Molecular Dynamics
- Quantum Chemistry
Background:
- Porphyrins exhibit distinct excited-state lifetimes.
- Understanding internal conversion is crucial for photophysical processes.
Purpose of the Study:
- Analyze internal conversion dynamics in Q and Q excited states of porphyrins.
- Identify factors causing different time constants in bare and functionalized porphyrins.
- Elucidate the role of specific molecular modes in population transfer.
Main Methods:
- Static calculation of per-mode reorganization energies.
- Nonadiabatic molecular dynamics simulations.
- Analysis of normal and essential modes.
Main Results:
- Identified key vibrational modes responsible for intersystem crossing.
- Quantified the contribution of different modes to population transfer.
- Evaluated statistical and nonstatistical analysis methods.
Conclusions:
- Specific molecular modes dictate internal conversion rates in porphyrins.
- Complementary computational methods provide a comprehensive understanding.
- Provides a physics-based framework for porphyrin photophysics.
Related Concept Videos
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.3K
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
2.3K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.8K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
1.8K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.0K
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
2.0K
01:17Pericyclic Reactions: Introduction
8.2K
Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic...
8.2K
01:16Thermal Sigmatropic Reactions: Overview
2.1K
Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in...
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in...
2.1K
02:13Energy Diagrams, Transition States, and Intermediates
16.1K
Free-energy diagrams, or reaction coordinate diagrams, are graphs showing the energy changes that occur during a chemical reaction. The reaction coordinate represented on the horizontal axis shows how far the reaction has progressed structurally. Positions along the x-axis close to the reactants have structures resembling the reactants, while positions close to the products resemble the products. Peaks on the energy diagram represent stable structures with measurable lifetimes, while...
16.1K