First principles study on the molecular structure and vibrational spectra of ketoprofen

The aim of this work was to compare the performance of different DFT methods at different basis sets in predicting geometry and vibration spectrum of ketoprofen. The molecular geometry and vibrational frequencies of ketoprofen have been calculated using five different density function theory (DFT) methods, including LSDA, B3LYP, mPW1PW91, B3PW91 and HCTH, with various basis sets, including 6-311G, 6-311+G, 6-311++G, 6-311+G (d, p) and 6-311++G (2d, 2p). The results indicate that mPW1PW91/6-311++G (2d, 2p) level is clearly superior to all the remaining density functional methods in predicting the bond lengths and bond angles of ketoprofen. Mean absolute deviations between the calculated harmonic and observed fundamental vibration frequencies for each method shows that LSDA/6-311G method is the best to predict vibrational spectra of ketoprofen comparing other DFT methods.