Support for Fluorophores

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. 

We have decorated different generations of polyphenylene dendrimers based on a biphenyl core with up to 16 perylenemonoimide chromophores at the periphery [67]. This has been achieved via the Diels-Alder reaction of a perylenemonoimide functionalized cyclopentadienone as a terminating reagent with the ethynyl precursor dendrimers. A strongly emitting nanoparticle is thus obtained. 

The energy dissipation in the dendrimer bearing a certain number of pery-lenemonoimide chromophores can be followed by applying time resolved fluorescence techniques. These measurements indicate excimer-like interactions among neighboring perylenemonoimide dyes. Furthermore, two types of motion are detected a rotation of the whole molecule and a fractional motion maybe of the dendrimer branch [68]. 

Polyphenylene Dendrimers Bearing a Functional Group in the Interior 

Moreover, a chromophore surrounded by a perfectly defined environment might be regarded as a potential candidate for SMS, allowing study of the interactions of a fluorophore with the surrounding matrix with a very high spatial resolution, which is currently under investigation. 

---