Infrared, Raman and NMR spectra, conformational stability, normal coordinate analysis and B3LYP calculations of 5-Amino-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde

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• 作者：Khaled Bahgat^a ; ^{khabahgat@yahoo.com} ; Talaat EL-Emary^b
• 关键词：5-Amino-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde ; DFT ; FT-IR ; FT-Raman ; NMR ; HOMO and LUMO
• 刊名：Journal of Molecular Structure
• 出版年：2013
• 出版时间：27 February, 2013
• 年：2013
• 卷：1034
• 期：Complete
• 页码：325-335
• 全文大小：778 K

文摘

FT Raman and IR spectra of the crystallized biologically active molecule, 5-Amino-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde (5-APHC, C₁₁H₁₁N₃O) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies of 5-APHC have been investigated with the help of B3LYP density functional theory (DFT) method with 6-31G(d) and 6-311+G(d,p) as basis set. The calculated molecular geometry has been compared with the experimental data. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQM) technique. The optimized geometry shows the co-planarity of the aldehyde group with pyrazole ring. Potential energy surface (PES) scan studies has also been carried out by ab initio calculations with B3LYP/6-311+G(d,p) basis set. The red shifting of NH₂ stretching wavenumber indicates the formation of N-H?O hydrogen bonding. ¹H and ¹³C NMR spectra were recorded and ¹H and ¹³C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-Vis spectrum of the compound was recorded in the region 200-400 nm and the electronic properties HOMO and LUMO energies were calculated by time-dependent TD-DFT approach. Mulliken charges of the 5-APHC molecule was also calculated and interpreted.