Calculated resonance vibrational raman optical activity spectra of naproxen and ibuprofen

Determining the absolute configuration of a molecule is possible by means of various chiroptical spectroscopic methods, one of them being vibrational Raman optical activity (VROA). By adopting a laser excitation wavelength in resonance with an electronic transition, the weak spectral signals can be selectively enhanced. We implement a Kohn−Sham methodology for the calculation of resonance and off-resonance VROA spectra to (S)-naproxen and (S)-ibuprofen and discuss their band patterns. The resonance enhancement of the VROA spectrum of (S)-naproxen at an incident wavelength of 514.5 nm caused by an absorption tail as well as the typical off-resonance behavior of the VROA spectrum of (S)-ibuprofen at the same incident wavelength can be well reproduced. VROA spectra are also predicted under full resonance conditions.