Solvent effects on the Raman absorption spectrum of epinephrine and norepinephrine by Monte Carlo and QM computational methods

The Raman spectra of epinephrine (EP) and norepinephrine (NP) were obtained by computational simulation in gaseous phase and diluted in water by both PCM and Monte Carlo explicit molecules methods by four levels of theory: HF and DFT (B3LYP, CAM-B3LYP and M06-2X) in combination with 6-311++G(d,p) basis functions, as PCM solvation was applied directly in Gaussian/09 and the Monte Carlo output from DICE was then single point simulated to obtain vibrational data. Raman shifts related to hydrogen bonds were identified. For EP, red shifts were obtained in peaks near 750 cm−1, 950 cm−1, 1300 cm−1 and 1600 cm−1 wavenumbers assigned to both aliphatic and catechol groups, indicating decrease in system energy and tendency to solvation. For NP, shifts near 750 cm−1 were slighter due to the change in the aliphatic group, as red shifts near 1250 cm−1 and 1600 cm−1 were similar as in EP due to the analogous catechol group. A comparison between HF/DFT methods was done and the better description of solvation was obtained by the Monte Carlo explicit approach as it identifies local molecular effects. •Raman shifts caused by hydrogen bonding effects have been identified.•Monte Carlo explicit solvation performed satisfactorily for solvent effects.•Slighter shifts presented by HF points out the necessity of electronic correlation.