Vibrational assignments and electronic structure calculations for 3-acetylcoumarin

Area of Science:

• Molecular Spectroscopy
• Computational Chemistry
• Quantum Chemistry

Background:

• 3-acetylcoumarin is a significant organic compound with potential applications.
• Understanding its vibrational properties is crucial for characterizing its structure and reactivity.
• Experimental spectroscopic data requires theoretical validation for comprehensive analysis.

Purpose of the Study:

• To investigate the vibrational spectra of solid 3-acetylcoumarin.
• To compute molecular electronic energy, geometrical structure, and harmonic vibrational spectra.
• To perform a complete vibrational assignment aided by theoretical harmonic frequency analysis.

Main Methods:

• Laser Raman spectroscopy (3500-50 cm⁻¹).
• Infrared (IR) spectroscopy (4000-400 cm⁻¹).
• Density Functional Theory (DFT) calculations using B3LYP/6-31G(d,p) and RHF/6-31G(d,p) levels.

Main Results:

• Experimental and theoretical vibrational spectra were obtained for 3-acetylcoumarin.
• B3LYP/6-31G(d,p) calculations accurately predicted geometrical parameters and vibrational frequencies.
• The frequency difference between the two carbonyl groups, attributed to conjugation, was well-reproduced by B3LYP.

Conclusions:

• The study successfully assigned the vibrational spectra of 3-acetylcoumarin.
• Theoretical calculations, particularly B3LYP, provide reliable predictions for molecular structure and vibrational properties.
• The findings enhance the understanding of conjugation effects on molecular vibrations in coumarin derivatives.