Synthesis, spectroscopy (vibrational, NMR and UV–vis) studies, HOMO–LUMO and NBO analysis of 8-formyl-7-hydroxy-4-methylcoumarin by ab initio calculations

• 8-Formyl-7-hydroxy-4-methylcoumarin has been synthesized.
• The title compound has been characterized experimentally and theoretically.
• The complete vibrational assignments and spectroscopic analysis were made.
• The geometrical parameters are in agreement with that of similar derivatives.
• NBO, MEP and thermodynamic properties of the title compound have been calculated.

In this work, 8-formyl-7-hydroxy-4-methylcoumarin has been synthesized and characterized by elemental analysis, FT-IR, FT Raman, 1H NMR, 13C NMR and UV–vis spectra. The molecular geometry, harmonic vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C chemical shift values of the title compound in the ground state have been calculated by using Hartree-Fock (HF) and density functional methods (B3LYP) with 6-311++G(d,p) as basis set. The vibrational assignments of wave numbers were interpreted in terms of potential energy distribution (PED) analysis and the scaled B3LYP/6-311++G(d,p) results show the good agreement with the experimental values. The UV spectra of investigated compound were recorded in the region of 230–500 nm in chloroform solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) in gas and CHCl3 theoretically and results were compared with experimental observations. The molecular stability arising from hyperconjugative interactions and charge delocalization have been analyzed using natural bond orbital (NBO) analysis. In addition, Frontier Molecular Orbitals (FMO), Molecular Electrostatic Potential (MEP) and thermodynamic properties of the studied compound such as heat capacity (C), entropy (S) and enthalpy changes (H) at different temperatures have been calculated.

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