FT-IR, FT-Raman, SERS spectra and computational calculations of 4-ethyl-N-(2′-hydroxy-5′-nitrophenyl)benzamide

Fourier transform infrared (FT-IR) and FT-Raman spectra of 4-ethyl-N-(2'-hydroxy-5'-nitrophenyl)benzamide were recorded and analyzed. A surface-enhanced Raman scattering (SERS) spectrum was recorded in silver colloid. The vibrational wavenumbers and corresponding vibrational assignments were examined theoretically using the Gaussian03 set of quantum chemistry codes. The red shift of the NH stretching wavenumber in the infrared spectrum from the computational wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. The simultaneous IR and Raman activation of the C=O stretching mode gives the charge transfer interaction through a pi-conjugated path. The presence of methyl modes in the SERS spectrum indicates the nearness of the methyl group to the metal surface, which affects the orientation and metal molecule interaction. The first hyperpolarizability and predicted infrared intensities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive subject for future studies of nonlinear optics. Optimized geometrical parameters of the title compound are in agreement with reported structures. Copyright (C) 2009 John Wiley & Sons, Ltd.