Structure, electronic, spectroscopic and reactivity investigations of pharmacologically active compound 1-acetyl-3-indolecarboxaldehyde - An experimental and theoretical approach

The experimental and theoretical studies on the structure and vibrations of 1-acetyl-3-indolecarboxaldehyde (AIC) have been carried out by utilising FT-IR, FT-Raman, FT-NMR and quantum chemical density functional theory (DFT) method. The FT-IR and FT-Raman spectra are recorded in the region 4000-400 cm−1 and 4000-100 cm−1, respectively. The geometry of AIC is optimised by B3LYP method with 6-31G**, 6-311++G** and cc-pVTZ basis sets. The more stable minimum energy conformer has been found by analyzing the potential energy profile. The fundamental vibrational frequencies, infrared intensities, Raman intensities and bonding features of this compound are determined. The HOMO and LUMO energy difference show that, the charge transfer occurs within the molecule. The electrostatic potential and thermodynamic properties of the compound at the different temperatures have been calculated. 1H and 13C NMR chemical shifts of the compound are determined by Gauge Invariant Atomic Orbital (GIAO) by using B3LYP/6-311++G** method. The electrostatic potential of AIC lie in the range +1.22e × 10−2 to −1.22e × 10−2. The limits of total electron density of the complex is +4.906e × 10−2 to −4.906e × 10−2.