Monofluorinated polycyclic aromatic hydrocarbons in Shpolskii spectroscopy

The basic requirement to achieve high resolution in Shpolʹskii spectroscopy is that the guest molecules fit well in the crystalline host alkane matrix, a condition that is usually met by polycyclic aromatic hydrocarbons (PAHs). Despite the electronegativity of the fluorine atom, which might be thought to strongly reduce the compatibility of guest and host, high-quality spectra can be recorded also for monofluorinated polycyclic aromatic hydrocarbons (FPAHs), as was shown for seven test analytes, viz. 1-fluoronaphthalene, 1-fluorophenanthrene, 3-fluorochrysene, 1-fluoropyrene, 2-fluorofluorene, 3-fluorofluoranthene and 9-flurobenzo[k] fluoranthene. Lamp-excited spectra were recorded in order to facilitate simultaneous excitation of PAHs and F-PAHs. The intensities and spectral qualities of the F-PAHs are similar to those of the parent compounds, but the 0-0 transitions are shifted from 0.5 to 7.3nm in the fluorescence mode; that is, the spectra do not overlap. For a number of F-PAHs, both the fluorescence and the phosphorescence transitions can be utilized.