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Updated: Jan 9, 2026

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Unraveling the Conformational and Electronic Landscape of 3‑Pyridinecarboxaldehyde: A Spectroscopic Journey through
Sung Man Park1, Hyojung Kim1, Chan Ho Kwon1
1Department of Chemistry and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chuncheon 24341, Republic of Korea.
Abstract:
3-Pyridinecarboxaldehyde (3-PCA) is a versatile building block, but its conformational and ionization behavior remains underexplored. Using high-resolution IR-resonant vacuum ultraviolet mass-analyzed threshold ionization spectroscopy and Franck-Condon simulations, two conformers, s-cis and s-trans, were identified in the gas phase, distinguished by adiabatic ionization energies of 76 123 ± 4 and 76 173 ± 4 cm-1, respectively, and revealing conformer-specific structural dynamics and frontier orbital changes during ionization. Computational analyses, including anharmonic and natural bond orbital studies, provided structural and electronic insights. Analysis of jet-cooled conformer populations indicated an S0-state energy difference of 40 ± 14 cm-1, while in the D0 state, the two conformers are essentially near-isoenergetic within experimental uncertainty (≈ -10 ± 14 cm-1). These results highlight the delicate balance of cationic conformer stability and its distinct ionization behavior. This work provides conformer-specific spectroscopic and theoretical benchmarks for understanding ionization-induced structural and stereoelectronic effects in formyl-substituted pyridines with implications for their reactivity and excited-state dynamics.
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