Molecular structure and vibrational spectra of ibuprofen using density function theory calculations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Ibuprofen is a widely used non-steroidal anti-inflammatory drug (NSAID).
• Accurate theoretical calculations are crucial for understanding drug properties and interactions.
• Density Functional Theory (DFT) is a powerful computational method for electronic structure calculations.

Purpose of the Study:

• To evaluate and compare the performance of five DFT methods (mPW1PW91, B3PW91, B3LYP, HCTH, LSDA) with five basis sets.
• To determine the most accurate computational approach for predicting the molecular geometry and vibrational spectrum of ibuprofen.
• To provide insights into the reliability of different DFT functionals and basis sets for pharmaceutical applications.

Main Methods:

• Molecular geometry optimization and harmonic frequency calculations using DFT.
• Employing five DFT functionals: mPW1PW91, B3PW91, B3LYP, HCTH, and LSDA.
• Utilizing five basis sets: 6-311G, 6-311++G, 6-311+G(d,p), 6-311++G(d,p), and 6-311++G(2d,2p).

Main Results:

• The mPW1PW91 method with 6-311++G(d,p) and 6-311++G(2d,2p) basis sets yielded optimized geometric parameters in best agreement with experimental data.
• The B3PW91 functional combined with the 6-311++G(2d,2p) basis set demonstrated superior accuracy in predicting the overall vibrational spectrum of ibuprofen.
• Significant variations in accuracy were observed among the tested DFT methods and basis sets for predicting ibuprofen's spectral properties.

Conclusions:

• The B3PW91/6-311++G(2d,2p) level of theory is recommended for accurate vibrational spectral predictions of ibuprofen.
• The choice of DFT method and basis set significantly impacts the accuracy of calculated molecular properties for ibuprofen.
• This study provides a valuable benchmark for selecting appropriate computational methods in the study of ibuprofen and similar pharmaceutical compounds.