Vibrational and theoretical analysis of pentyl-4-benzoyl-1-[2,4-dinitrophenyl]-5-phenyl-1H-pyrazole-3-carboxylate

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• IR spectrum of the pyrazole derivative has been measured.
• The rotational barriers for the critical flexible bonds has been plotted and discussed.
• Six conformational isomers have been obtained through relaxed scan.
• Two weak H bondings for the most stable conformer have been obtained.
• Vibrational analysis of the most stable conformer was performed by BLYP and B3LYP.

Infrared spectrum of the compound, pentyl-4-benzoyl-1-[2,4-dinitrophenyl]-5-phenyl-1H-pyrazole-3-carboxylate (PBDPPC) has been measured. Conformational search through relaxed scan has been carried out to find the most stable conformational isomer. After the full geometry optimization for the most stable conformer using B3LYP and BLYP hybrid functionals of Density Functional Theory (DFT), vibrational normal modes have been calculated at the same theoretical levels. Potential Energy Distribution (PED) of each normal mode has been calculated by means of VEDA4 to obtain contributions of internal coordinates to the normal modes. Natural Bond Orbital (NBO) analysis has been performed to get insights into the possible hydrogen bonding sites for all the conformational isomers.

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