Experimental (FT-IR and FT-Raman) and spectroscopic investigations, electronic properties and conformational analysis by PES scan on 2-methoxy-5-nitrophenol and 2-methoxy-4-methylphenol

Abstract

A complete vibrational and molecular structure analysis is performed based on the quantum mechanical approach by HF and DFT calculations. On the basis of the calculated and experimental results the assignments of the fundamental frequencies are examined. The available experimental results are compared with the theoretical data. A low value of HOMO LUMO energy gap suggests the possibility of intramolecular charge transfer in the molecule. This plays an important role in the significant increase of the β value, which is a property to exhibit nonlinear optical (NLO) activity. The NBO result reflects the charge transfer mainly due to lone pairs. Theoretical ¹H and ¹³C chemical shift values (with respect to TMS) are reported and compared with experimental data which shows the agreement for both ¹H and ¹³C. Predicted electronic absorption spectra from TD-DFT calculations are analysed and they are mainly derived from the contribution of the π → π* band. The predicted NLO properties are much greater than those of urea.