Valence structures of aromatic bioactive compounds: a combined theoretical and experimental study

Area of Science:

• Computational chemistry
• Quantum chemistry
• Spectroscopy

Background:

• Aryl bioactive compounds are crucial in medicinal chemistry.
• Understanding their electronic structure is key to predicting their properties and reactivity.
• Recent isolation of 2-phenylethanol (2PE), p-hydroxyphenylethanol (HPE), and 4-hydroxybenzaldehyde (HBA) necessitates detailed electronic structure analysis.

Purpose of the Study:

• To elucidate the valence electronic structures of 2PE, HPE, and HBA.
• To investigate the influence of side chains on the aromaticity and spectral properties of these benzene derivatives.
• To compare theoretical predictions with experimental measurements of electronic and vibrational spectra.

Main Methods:

• Density functional theory (DFT) for electronic structure calculations.
• Simulations of Infrared (IR) spectra, including solvent effects using the polarizable continuum model (PCM).
• Experimental measurement of valence binding energy spectra and analysis using outer-valence Green function (OVGF) calculations.

Main Results:

• Side chains induce electron charge redistribution, affecting the aromaticity of the benzene ring.
• Simulated IR spectra reveal side-chain specific features, with significant red-shifts and enhancements in O-H stretching vibrations due to solvent effects.
• Experimental first ionization energies were determined and found to be in good agreement with OVGF predictions.
• Significant spectral peak splitting was observed for HPE in aqueous environments.

Conclusions:

• The electronic structures and spectral properties of 2PE, HPE, and HBA are significantly influenced by their side chains.
• Theoretical calculations accurately predict experimental spectral features and ionization energies.
• The study provides valuable insights into the electronic behavior of these bioactive aryl compounds, aiding in their further application and development.