Raman and photoacoustic infrared spectra of fluorene derivatives: Experiment and calculations.

International audienceRaman and photoacoustic (PA) IR spectra of fluorene and four derivs. (2,3-benzofluorene, 2-methylfluorene, 2-ethylfluorene and 1,8-dimethylfluorene) were recorded and analyzed in this investigation. Mid- and far-IR PA spectra were examd. from about 2000 to 100 cm-1. The Raman spectra spanned the same wavenumber range. Obsd. bands in both PA and Raman spectra were compared with DFT (harmonic) and variational (anharmonic) calcns., and with published spectra. The DFT calcns. provided single-mol. frequencies, whereas the variational method yielded results for both monomeric and dimeric species. Many previously unknown bands, including numerous features due to combination and overtone transitions, were identified and assigned in this work