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Three-Dimensional Energy Transport in Highly Luminescent Host−Guest Crystals: A Quantitative Experimental and Theoretical Study

Lars Poulsen,^† Mikael Jazdzyk,^‡ Jean-Edouard Communal,^§ Juan Carlos Sancho-García, Andrea Mura,^§ Giovanni Bongiovanni,^§ David Beljonne, Jérôme Cornil, Michael Hanack,^‡ Hans-Joachim Egelhaaf,*^† and Johannes Gierschner*^†;

Contribution from the Institute of Physical and Theoretical Chemistry, University of Tbingen, Auf der Morgenstelle 8, D-72076 Tbingen, Germany, Institute of Organic Chemistry, University of Tbingen, Auf der Morgenstelle 18, D-72076 Tbingen, Germany, Dipartimento di Fisica and Istituto Nazionale di Fisica della Materia, Universit degli Studi di Cagliari, I-09042 Monserrato (CA), Italy, Laboratory for Chemistry of Novel Materials, Center for Research in Molecular Electronics and Photonics, University of Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium, and Christian-Doppler Laboratory for Surface Optical Methods, Institute for Semiconductor Physics, Johannes-Kepler-University, Altenbergerstr. 69, Linz, Austria

J. Am. Chem. Soc., 2007, 129 (27), pp 8585–8593

DOI: 10.1021/ja0714437

Publication Date (Web): June 12, 2007

†

Institute of Physical and Theoretical Chemistry, University of Tübingen.

‡

Institute of Organic Chemistry, University of Tübingen.

Università degli Studi di Cagliari.

University of Mons-Hainaut.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

Johannes-Kepler-University.

, hegelhaaf@konarka.com, ; , johannes@averell.umh.ac.be

Abstract

We present a combined experimental and theoretical study on energy transfer processes in a well-defined three-dimensional host−guest system, which allows for high chromophore concentrations while maintaining the highly luminescent properties of the molecules in solution. The self-assembled, nanostructured system with a defined ratio of included donor and acceptor molecules is amenable to quantitative comparison between experiment and theory. Experimentally, energy migration is monitored by steady-state and time-resolved fluorescence spectroscopy. From the theoretical side, the energy transfer process is modeled by a Monte Carlo approach including homo and hetero transfer steps with multi-acceptor distribution. In this dense system, the classical Förster point-dipole approach for energy transfer breaks down, and the hopping rates are therefore calculated on the basis of a quantum-chemical description of the donor and acceptor excited states. Thereby, the true directionality of the excitation diffusion is revealed. Excellent agreement with experimental donor and acceptor decays and overall transfer efficiencies is found. Even at low acceptor concentrations (down to 0.1%), efficient energy transfer over distances as large as 25 nm was observed due to rapid energy migration through a series of homo-transfer steps with preference along one direction of the structure.

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