The S2-S0 fluorescence excitation spectra ofxanthione (XT) and azulene (AZ) complexed with 1 or 2 molecules of the C1 to C10 n-alkanes and the C1 to C6 perfluoro-n-alkanes have been measured. The 1:1 complexes exhibit microscopic solvent shifts, Δ \ ̄gn, which are larger for the alkanes than the corresponding perfluoroalkanes, despite the larger molecular polarizability of the latter. The values of Δ \ ̄gn increase monotonically with carbon number of the adduct to C10 in 1:1 n-alkane complexes with XT and to C5 in 1:1 n-alkane complexes with AZ. However, Δ \ ̄gn exhibits no further increase beyond C2 in 1:1 perfluoro-n-alkane complexes with XT and beyond C3 in 1:1 perfluoro-n-alkane complexes with AZ. The results are interpreted in terms of a model in which the n-alkanes stretch out along the long axis of the chromophore and 'wet' its surface whereas the perfluoro-n-alkanes with carbon numbers ≥ 3 away from the surface of the chromophore and are 'non-wetting'.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Condensed Matter Physics
- Atomic and Molecular Physics, and Optics
- Surfaces and Interfaces