No abstract

Perylenemonoimide chromophores, attached to a small dendron arm embedded in the polymer hosts Zeonex, poly(vinylbutyral), and poly(methyl methacrylate), are studied by means of laser-induced confocal fluorescence detection. Transient fluorescence intensity exhibits dark periods on two different time scales: on a 100 µs time scale and on a considerably longer time scale, ranging from 100 ms to as much as tens of seconds under high-vacuum conditions. The exponentially distributed short "off" times are attributed to triplet excursions of the molecule. The long-lived dark states follow a power-law distribution and are discussed in terms of the formation of radical anions/cations via electron tunneling processes.

Two new synthetic approaches to terrylenediimides, highly photostable fluorescent dyes, are described. For the first time terrylenediimide has been synthesised in a straightforward procedure that makes large quantities available. The second route includes an efficient cross-coupling reaction followed by a cyclodehydrogenation. Monofunctionalisation of the imide structure allows terrylenediimides now to be coupled with a variety of compounds, for example, by Suzuki cross-coupling, which can lead to an array of terrylenediimides with new functional groups such as hydroxy, amino, or carboxy groups needed to link up with other molecules. The functionalisation in the bay region is used to tune the properties of terrylenediimides and extend the range of applications, for example, by introducing water solubility. These tetrasubstituted terrylenediimides offer, depending on the substituents used, exciting features such as good solubility in common organic solvents, water solubility, or NIR absorption.

The photophysics of a dendrimer containing four donor chromophores and one acceptor chromophore are studied at the single-molecule level. Upon excitation of the donors exclusive acceptor emission is observed due to efficient Förster energy transfer. For 70% of the molecules donor emission is observed after bleaching of the acceptor, leading to a reduction of the Förster energy transfer efficiency. Furthermore, we demonstrate that in this molecular system the donor chromophores do not bleach by a triplet-sensitized photooxidation.