Spectroscopic identification of gauche and trans conformers in L-phenylalanine Fiber and hydrogel via CH/CD stretching vibrations
Abstract
Weak molecular interactions and subtle conformational variations can directly modulate C-H bond strength, yet their spectroscopic signatures as a probe of polymorphism remain largely unexplored. Here, chiral phenylalanine in anhydrous Form I, hemi-hydrated fiber, and hydrogel states were investigated by Raman, IR, and vibrational circular dichroism (VCD) spectroscopy combined with DFT calculations, focusing on the C-H stretching region. Isotopic substitution combined with VCD analysis reveals coexistence of gauche (G -) and trans (T) conformers in the fiber and hydrogel. The methine C-D stretching vibration of the T conformer exhibits a marked blue shift relative to the G-conformer, indicating strengthening of the C-H bond induced by close-range electrostatic repulsion from a neighboring NH₃⁺ group. Raman analysis of the hydrogel demonstrates preservation of the local G -/T hydrogen-bonded pairing motif and associated π-π interactions despite the absence of long-range crystalline order. These results demonstrate that C-H stretching vibrations serve as highly sensitive reporters of weak molecular interactions and local structural organization in condensed phases.
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BibTeX
@article{lin2026spectroscopic,
title = {{Spectroscopic identification of gauche and trans conformers in L-phenylalanine Fiber and hydrogel via CH/CD stretching vibrations}},
author = {Ke Lin and Botao Yao and Zhiqiang Wang and Anne Zehnacker-Rentien},
journal = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy [1994-...]},
year = {2026},
month = oct,
doi = {10.1016/j.saa.2026.128297},
url = {https://hal.science/hal-05798609v1},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - JOUR
TI - Spectroscopic identification of gauche and trans conformers in L-phenylalanine Fiber and hydrogel via CH/CD stretching vibrations
AU - Ke Lin
AU - Botao Yao
AU - Zhiqiang Wang
AU - Anne Zehnacker-Rentien
PY - 2026
DA - 2026/10/14
JO - Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy [1994-...]
DO - 10.1016/j.saa.2026.128297
UR - https://hal.science/hal-05798609v1
AB - Weak molecular interactions and subtle conformational variations can directly modulate C-H bond strength, yet their spectroscopic signatures as a probe of polymorphism remain largely unexplored. Here, chiral phenylalanine in anhydrous Form I, hemi-hydrated fiber, and hydrogel states were investigated by Raman, IR, and vibrational circular dichroism (VCD) spectroscopy combined with DFT calculations, focusing on the C-H stretching region. Isotopic substitution combined with VCD analysis reveals coexistence of gauche (G -) and trans (T) conformers in the fiber and hydrogel. The methine C-D stretching vibration of the T conformer exhibits a marked blue shift relative to the G-conformer, indicating strengthening of the C-H bond induced by close-range electrostatic repulsion from a neighboring NH₃⁺ group. Raman analysis of the hydrogel demonstrates preservation of the local G -/T hydrogen-bonded pairing motif and associated π-π interactions despite the absence of long-range crystalline order. These results demonstrate that C-H stretching vibrations serve as highly sensitive reporters of weak molecular interactions and local structural organization in condensed phases.
SN - 1386-1425
SN - 1873-3557
ER -