Rylene dyes

Due to their high chemical stability, their high tendency to physisorb on silica, and their high fluorescence quantum yields, rylene dyes (27) and (28) (Scheme 6) were chosen as tags for the catalysts.65 They were shown not to influence the actual catalytic process. Known zirconium... 

The attachment of a distinct number of fluorescent dyes at the periphery of a stiff three-dimensional nanoparticle is of fundamental interest to study interactions between single chromophores in close vicinity to each other. We chose as a dye one of the rylene series, perylenemonoimide, for the decoration of our polyphenylene dendrimers due to their outstanding properties. Rylene dyes show an exceptional chemical and photochemical stability and therefore are well suited for single molecule spectroscopy (SMS) [661. 

On the other hand, when two glutamic acids were attached to the dye molecules, the possibility arose of connecting two or more nanoparticles with rylene dyes. Thus, the designed TDI 38 with two dicarboxylic acid anchors at the imide nitrogen atoms was synthesized by the same procedure as described above. The dianhydride 43 was obtained by complete saponification of TDI 42 [7]. Further imidization of 43 and p-glutamic acid afforded TDI 38 [58] (Scheme 10). The complexation between TDI 38 and QDs led to the formation of QD dimers and trimers, for which energy transfer from the QDs to the TDI bridge was observed. 

By furnishing rylene dyes with dicarboxylate anchors, a versatile route for the preparation of extraordinarily stable dye/QD complexes has been established. It was pointed out that, by proper choice of dye and QD compruients, a broad spectral range from the visible up to the near infrared could be covered and the efficiency of EET easily tuned. 

Scheme 11 Rylene dyes synthesized by the group of K. Mullen that were used for ligation with LHCII...

Quantum chemical model calculations are useful tools for gaining further insight into the atomistic details of the photophysical properties considered in this chapter. We will describe a number of studies that have helped to develop a better understanding of the optical spectra of rylene dyes and the EET processes in simple donor-acceptor dyads such as 1 and 2. 

Due to their direct relation to the spectral overlap integral, see Eq. (9), the emission and absorption spectra of the dye molecules are of interest in the context of EET processes. The simplest way to model excitation spectra employs the calculation of vertical energy separations, i.e., the separation of the Bom-Oppenheimer potential energy surfaces of the initial state and the final state at the equilibrium structure of the initial state. This energy separation is expected to coincide with the absorption maximum, as rationalized by the Franck-Condon principle (see for example [135]). This assumption is not always appropriate, rylene dyes being a prominent example. These dyes feature a strong 0-0 transition and a pronounced vibronic progression that is even visible in solution at room temperature (see for example [137]). A detailed simulation of the vibrational substructure of the absorption and emission bands is necessary to understand the details of the spectram. 

Rylenes XXV represent a further interesting class of NIR-dyes [YUA 13,SCH 08]. The substituents Rl and R2 influence the solubility of these neutral compounds. Nevertheless, these chromophores sensitively change their absorption spectra upon change of the surrounding, which was discussed as a result of H-aggregation [YUA 13]. 

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