Electronic structure and intramolecular interactions in three methoxyphenol isomers

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Methoxyphenol isomers exhibit complex electronic structures influenced by intramolecular interactions.
• Understanding these interactions is crucial for predicting molecular behavior and properties.

Purpose of the Study:

• To investigate the electronic structures and intramolecular interactions of three methoxyphenol positional isomers and their rotamers.
• To compare experimental core X-ray photoelectron spectroscopy data with theoretical calculations.

Main Methods:

• Core X-ray photoelectron spectroscopy (XPS) was employed.
• Quantum mechanical calculations were utilized to model electronic structures and interactions.
• Calculations were benchmarked against experimental data for enthalpy of formation and rotational constants.

Main Results:

• Accurate theoretical models were established by good agreement with benchmark data.
• Calculated C 1s photoelectron spectra closely matched experimental results for selected rotamers.
• Conformational effects on binding energies were analyzed, revealing small differences (<0.15 eV) for 3-methoxyphenol and even smaller (<0.05 eV) for 4-methoxyphenol.
• Significant shifts in methyl carbon binding energy were observed in higher energy rotamers of 2-methoxyphenol due to OH⋯OCH3 hydrogen bonding.

Conclusions:

• The study successfully elucidates the electronic structures and conformational effects in methoxyphenol isomers.
• Quantum mechanical calculations combined with XPS provide a powerful tool for analyzing molecular interactions.
• Relaxation energies were quantified, with phenyl carbons showing ~0.5 eV and methyl groups ~1.3 eV.