Electronic Properties of π-conjugated Materials II - Universität ...

Oral Presentations – 3 π 2011
Electronic coupling in molecular dimers: Single molecule
studies and quantum chemical calculations
F. P. Diehl, C. Roos, A. Köhn and T. Basché
Universität Mainz
A series of molecular dimers (Dye-Dye) was prepared by increasing the intermolecular distance
by a growing number n (n = 0 − 3) of phenyl-rings. Individual dimers were investigated by
time and frequency resolved single molecule spectroscopy at T = 1.2 K. With increasing distance
between the two chromophores, a transition from the weak (incoherent energy transfer) to the
strong (coherent energy transfer) coupling regime is observed. �e signatures of the various
coupling limits are reflected in the number of zero-phonon lines and the fluorescence lifetimes of
the dimers. At intermediate distances the particular site energy difference for single dimers tips
the scale between the two coupling regimes; hence either weak or strong coupling is observed for
individual dimers. Electronic coupling strengths V as deduced from single molecule excitation
spectra are in good agreement with results from quantum chemistry.
48