Contents
1 Introduction . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 62
2 Preparation and Photophysical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.1 Multichromophoric Systems Tailored for Energy Transfer Applications . . . . . . . . . . 63
2.2 Complexes from Colloidal Semiconductor Quantum Dots and Organic Dye
Molecules . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 74
2.3 Biological–Chemical Hybrids Built from Light-Harvesting Complexes . . . . . . . . . . . 81
2.4 Dye Molecules in Cholesteric Phases: Towards Lasing Applications. . . . . . . . . . . . . . 86
3 Single-Molecule Studies of Electronic Excitation Energy Transfer . . . . . . . . . . . . . . . . . . . . . . 93
3.1 Flexibility of Donor–Acceptor Dyads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
3.2 Control of the Energy Transfer Pathway by Dual Pulse Excitation . . . . . . . . . . . . . . . . 94
3.3 Read-Out of the Spin State of a Single Molecule by the Emission from Proximate
Fluorophores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.4 Rates and Mechanism of Energy Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4 Theoretical Description of Vibronic Spectra and Electronic Coupling . . . . . . . . . . . . . . . . . . . 101
4.1 Vibronic Spectra of PMI and PDI Chromophores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.2 Electronic Coupling in Donor–Acceptor Dyads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
1 Introduction
The evolution of specific properties resulting from the formation of complex
molecular assemblies is an important and longstanding issue in contemporary
science. In this chapter, the controlled organization of organic, inorganic, and
biological components into molecular assemblies via covalent and non-covalent
(e.g., electrostatic) interactions is presented. The central issue in these studies is
control of the photophysical properties of the constructs, which are determined by
the nature of the building blocks and by their organization into assemblies on
different length scales. Although electronic excitation energy transfer (EET)
between molecules or molecules and colloidal semiconductor quantum dots
(QDs) is of chief importance, the effect of helical superstructures on the emission
of dye molecules has also been considered. Stationary and time-resolved absorption
and emission spectroscopy proved to be valuable tools for characterization of the
properties of such molecular assemblies. A synthetic challenge has been to provide
complex donor–acceptor dyads and triads with high structural perfection with
respect to the distance and orientation of the chromophores. As described in
Sect. 2.1, rylene tetracarboxydiimide building blocks in conjunction with rigid
oligo(phenylene) bridges offer a versatile approach for electronic and geometrical
control of EET processes. A further advantage of this class of dye molecules are
their favorable properties for single-molecule spectroscopy (SMS). Following
proper functionalization by dicarboxyl anchors, rylene dyes have also been attached
to QDs. Owing to the chemical flexibility of the dye as well as the QD components,
various options exist for tuning the spectral parameters of QD/dye hybrids, as
62
T. Basche ´ et al.
1 Introduction . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 62
2 Preparation and Photophysical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.1 Multichromophoric Systems Tailored for Energy Transfer Applications . . . . . . . . . . 63
2.2 Complexes from Colloidal Semiconductor Quantum Dots and Organic Dye
Molecules . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 74
2.3 Biological–Chemical Hybrids Built from Light-Harvesting Complexes . . . . . . . . . . . 81
2.4 Dye Molecules in Cholesteric Phases: Towards Lasing Applications. . . . . . . . . . . . . . 86
3 Single-Molecule Studies of Electronic Excitation Energy Transfer . . . . . . . . . . . . . . . . . . . . . . 93
3.1 Flexibility of Donor–Acceptor Dyads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
3.2 Control of the Energy Transfer Pathway by Dual Pulse Excitation . . . . . . . . . . . . . . . . 94
3.3 Read-Out of the Spin State of a Single Molecule by the Emission from Proximate
Fluorophores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.4 Rates and Mechanism of Energy Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4 Theoretical Description of Vibronic Spectra and Electronic Coupling . . . . . . . . . . . . . . . . . . . 101
4.1 Vibronic Spectra of PMI and PDI Chromophores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.2 Electronic Coupling in Donor–Acceptor Dyads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
1 Introduction
The evolution of specific properties resulting from the formation of complex
molecular assemblies is an important and longstanding issue in contemporary
science. In this chapter, the controlled organization of organic, inorganic, and
biological components into molecular assemblies via covalent and non-covalent
(e.g., electrostatic) interactions is presented. The central issue in these studies is
control of the photophysical properties of the constructs, which are determined by
the nature of the building blocks and by their organization into assemblies on
different length scales. Although electronic excitation energy transfer (EET)
between molecules or molecules and colloidal semiconductor quantum dots
(QDs) is of chief importance, the effect of helical superstructures on the emission
of dye molecules has also been considered. Stationary and time-resolved absorption
and emission spectroscopy proved to be valuable tools for characterization of the
properties of such molecular assemblies. A synthetic challenge has been to provide
complex donor–acceptor dyads and triads with high structural perfection with
respect to the distance and orientation of the chromophores. As described in
Sect. 2.1, rylene tetracarboxydiimide building blocks in conjunction with rigid
oligo(phenylene) bridges offer a versatile approach for electronic and geometrical
control of EET processes. A further advantage of this class of dye molecules are
their favorable properties for single-molecule spectroscopy (SMS). Following
proper functionalization by dicarboxyl anchors, rylene dyes have also been attached
to QDs. Owing to the chemical flexibility of the dye as well as the QD components,
various options exist for tuning the spectral parameters of QD/dye hybrids, as
62
T. Basche ´ et al.