Molecular charge distributions, Vibrational frequency and Stability studies on 1H-indole-3-carbaldehyde and (Z)-indol-3-ylidenemethanol: DFT Approach


1H-indole-3-carbaldehyde (A) and its enol-tautomer, (Z)-indol-3-ylidenemethanol (B) have been examined using B3LYP/6-311++G(d,p), M06/6-311++G(d,p), wB97xD/6-311++G(d,p) and MP2/6-311++G(d,p) methods. The EHOMO, ELUMO, Δ(EHOMO-LUMO), dipole moment, softness (σ), chemical hardness (η), chemical potential (µ), ionization potential (IP), electron affinity (EA), nucleophilicity index (ω) and thermodynamic parameters were calculated and discussed. The band gap revealed that compound A would be hard, more stable thermodynamically and less labile than B. This this was in agreement with the total energy, chemical hardness and chemical softness calculated for the compounds. The Molecular electrostatic potential (MEP) map showed that N-H hydrogen and carbonyl oxygen are the most plausible potential site for nucleophilic (blue color) and electrophilic (red color) activities for compound A. For compound B, O-H hydrogen and N of indole are most plausible site for nucleophilic and electrophilic activities. Critical analysis of the charge population distributions shows that charge distributions respond more to the basis sets rather than the computational methods used for the calculations.