Investigation of molecular dimers by ensemble and single molecule spectroscopy

• Published in: Journal of luminescence Vol. 98; no. 1; pp. 23 - 33
• Main Authors: Christ, Th, Petzke, F, Bordat, P, Herrmann, A, Reuther, E, Müllen, K, Basché, Th
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-07-2002; Elsevier
• Subjects: Atomic and molecular clusters; Atomic and molecular physics; Chemical Sciences; Electronic interactions; Exact sciences and technology; Excitons; Fluorescence and phosphorescence spectra; Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion); Molecular aggregates; Molecular properties and interactions with photons; Molecular spectra; Physics; Single molecule spectroscopy; Studies of special atoms, molecules and their ions; clusters; Visible spectra; Molecular aggregates; Excitons; Single molecule spectroscopy; Electronic interactions; Fluorescence spectrum; Molecular clusters; Nitrogen heterocycle; Emission spectra; Electron interaction; Visible spectra; Dimers; Absorption spectra; Experimental study; Organic compounds
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/S0022-2313(02)00247-8

We have investigated molecular dimers with different electronic coupling strengths by bulk and single molecule spectroscopy. In one of the dimers the two monomers (perylene-monoimide) are directly connected via a single bond while in the other one they are separated by the benzil motif. The close proximity of the monomers in the first case gives rise to excitonic band splitting which is clearly observable in the bulk absorption spectra. For the benzil structure the electronic interactions are governed by Förster-type energy hopping between the monomers. Fluorescence intensity trajectories at the single molecule level show one-step and two-step bleaching behaviour which appears to be very similar for both dimers. However, emission spectra recorded simultaneously with the trajectories indicate spectral changes which allow to distinguish between weakly and strongly coupled dimers. In the latter case the spectral shape changes significantly when excitonic coupling has been lifted because of photochemical transformation of one of the monomers.