Molecular structure and vibrational spectra studies on antipyrine derivative, 4-(2,3,4-trihydroxybenzylideneamino) antipyrine

• DFT studied on the molecular structures and vibration spectra of THBAP.
• Gaussian 09 was used to optimize the structure and calculate the frequencies.
• The performance of the different DFT and basis sets were examined.
• LanL2DZ and SDD are the best for predicting the structure of THBAP.
• mPW1PW91/6-311G is the best for predicting the vibration spectra of THBAP.

The molecular geometry, theoretical harmonic frequencies and infrared intensities of 4-(2,3,4-trihydroxybenzylideneamino) antipyrine (THBAP) were calculated using different density functional methods (LSDA, mPW1PW91, B3LYP and HCTH) with various basic sets, including 3-21G, 6-311G, LanL2DZ, and SDD. The purpose of this research is to compare the performance of different density functional theory (DFT) methods at different basis sets in predicting geometry and vibration spectrum of THBAP. The optimized geometric band lengths and bond angles obtained by using mPW1PW91 at both LanL2DZ and SDD basic sets show the best agreement with the experimental data. A comparison between the observed fundamental vibrational frequencies of THBAP and the calculated results has been made and the result indicates that the mPW1PW91/6-311G level is superior to all the remaining levels for predicting all the vibration spectra on average for THBAP.

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