A comparative analysis of isomerization pathways in 3- and 4-styrylpyridines
Derreck W Nongspung1, Aditya N Panda1
1Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, India. anp@iitg.ac.in.
Physical Chemistry Chemical Physics : PCCP
|February 25, 2026
Summary
Computational studies reveal isomer-specific pathways for photoinduced isomerization and cyclization in 3-styrylpyridine (3-STPY) and 4-styrylpyridine (4-STPY). The cis-isomer pathways involve lower energy barriers for isomerization and cyclization compared to trans-isomer pathways.
Area of Science:
- Photochemistry
- Computational Chemistry
- Organic Chemistry
Background:
- Styrylpyridine isomers (3-STPY and 4-STPY) exhibit distinct conformational flexibilities due to nitrogen atom placement.
- Understanding excited-state dynamics is crucial for controlling photochemical reactions.
Purpose of the Study:
- To investigate and compare isomerization and cyclization pathways in 3-STPY and 4-STPY.
- To elucidate the non-radiative decay channels and energy barriers involved in photoexcitation.
Main Methods:
- Second-order Møller-Plesset (MP2) and algebraic diagrammatic construction to the second-order (ADC(2)) calculations.
- Complete active space self-consistent field (CASSCF) method to locate minimum energy conical intersection structures (MECIs).
- Analysis of image-dependent pair potential (IDPP) pathways for isomerization and cyclization.
Main Results:
- 3-STPY shows greater conformational diversity than 4-STPY due to symmetry differences.
- Isomerization via twisted-pyramidalized MECIs from the cis side has lower energy barriers than from the trans side.
- Relaxation to cyclized MECIs occurs with minimal energy barriers for both isomers.
Conclusions:
- Isomer-specific pathways dictate the photoinduced isomerization and cyclization of styrylpyridine derivatives.
- The cis-isomer pathways are more favorable for both isomerization and cyclization.
- Findings provide mechanistic insights into excited-state processes in these molecules.
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