Molecular structure, FT-IR, FT-Raman, NMR studies and first order molecular hyperpolarizabilities by the DFT method of mirtazapine and its comparison with mianserin

Mirtazapine (±)-1,2,3,4,10,14b-hexahydro-2-methylpyrazino(2,1-a)pyrido(2,3-c)(2)benzazepine is a compound with antidepressant therapeutic effects. It is the 6-aza derivative of the tetracyclic antidepressant mianserin (±)-2-methyl-1,2,3,4,10,14b-hexahydrodibenzo[c,f]pyrazino[1,2-a]azepine. The FT-IR and FT-Raman spectra of mirtazapine have been recorded in 4000–400 cm−1 and 3500–10 cm−1, respectively. The optimized geometry, energies, nonlinear optical properties, vibrational frequencies, 13C, 1H and 15N NMR chemical shift values of mirtazapine have been determined using the density functional theory (DFT/B3LYP) method. A comparison of the experimental and theoretical results of mirtazapine indicates that the density-functional B3LYP method is able to provide satisfactory results for predicting vibrational and NMR properties. The experimental and calculated results for mirtazapine have also been compared with mianserin.

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► The FT-IR and FT-Raman spectra of mirtazapine were recorded.
► Structure, electronic properties, NMR and vibrational spectra were investigated using DFT.
► The experimental and DFT results for mirtazapine were compared with mianserin.