Molecular structure and vibrational spectra of 7-Methoxy-4-methylcoumarin by density functional method

• Theoretical molecular structure of 7-Methoxy-4-methylcoumarin determined.
• Two stable conformers were obtained.
• Experimental FT-IR and Raman spectra recorded.
• Harmonic vibrational frequencies were calculated.
• Combined experimental and theoretical wavenumbers are assigned to various modes of vibrations.

In the present study, as a result of detailed structural and conformational analysis of the 7-Methoxy-4-methylcoumarin, two different conformers have been obtained. The FT-IR and Raman spectra were recorded in the region 4000–400 cm−1 and 3500–50 cm−1, respectively. Vibrational frequences of the title compound were calculated by Becke3–Lee–Yang–Parr (B3LYP) functional using 6-311++G(d,p) basis sets.The ground state energies and dipole moments have also been computed. The calculated and scaled frequencies were compared with experimental values and on the basis of this comparison and total-energy distribution data assignments of fundamental vibrational modes were examined. The differences between the observed and scaled wavenumber values of most of the fundamentals are very small.

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