Abstract
The study of the spectroscopic properties of molecular complexes of perylene has been extended to naphthalene. Calculations extrapolated from earlier work predict a deviation from center-of-mass, parallel-plane geometry, and this prediction is supported by the experimental data. The complexes show a very large red-shift, of 748 cm −1, which is almost twice that of benzene. A 2 : 1 complex was also observed, exhibiting a nearly harmonic shift, to 1443 cm −1. The spectra show little perturbation of the in-plane modes from the free perylene case, but strong new low-frequency bands are seen, which may be attributed to complexation-induced deformation of the perylene ground state. The most important result is that strong resonance fluorescence, which was suppressed in small molecule complexes of perylene, is observed for the perylene-naphthalene 353 cm −1 in- plane mode. By contrast, excitation into combinations of out-of-plane deformation modes in the same energy region effectively eliminated the resonance fluorescence. This is, therefore, an important case where a mode of a big molecule is decoupled from the quasi-continuum, and develops small-molecule character.
Published Version
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