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Branching out: Stiff, aromatic dendrimers made up of five and seventeen pyrene units, respectively, are synthesized, characterized, and compared with two model compounds. The rigid and strongly twisted structure allows a precise spatial arrangement in which each unit is a chromophore. The high extinction coefficients and fluorescence quantum yields make these dendrimers attractive candidates for use as fluorescence labels.

Pyrene is one of the most important and thoroughly investigated organic chromophores. Among the attractive features of pyrene is its exceptionally long fluorescence lifetime, [1] the sensitivity of its excitation spectra to microenvironment changes, [2] and its high propensity for forming excimers. [3] This excimer formation has been utilized over the last 50 years in the investigation of water-soluble polymers, making pyrene, by far, the most frequently applied dye in fluorescence-labeled polymers. [4] Despite its chemical stability and high charge carrier mobility, its strong tendency to form excimers leads to a red-shift of its emission as well as a decrease in its fluorescence efficiency in condensed media, which has prohibited its use as an emissive material in organic light-emitting devices (OLED)s.Since the report of the first double-layer thin-film OLED by the Kodak Company in 1987, [5] OLEDs have attracted enormous attention in the scientific community thanks to their high technological potential for the next generation of fullcolor-flat-panel displays and lighting applications. [6,7] Whether polymers [8] or small molecules, [5] to date only red-and greenemitters have shown sufficient efficiencies and lifetimes to be of commercial value. [7] Here, we present a novel non-aggregating polypyrene, which can be synthesized via a simple three-step chemical route from pyrene in good yields. Our poly-7-tert-butyl-1,3-pyrenylene (3) shows a high solid-state fluorescence quantum yield with blue emission, excellent solubility and stability, no aggregation in thin films, and good electro-optical performance in single-layer OLEDs.The use of pyrene, a large conjugated aromatic system, as emitting material in OLED applications has been limited, due to aggregation between planar pyrene molecules. The formation of p-aggregates/excimers causes the quenching of fluorescence, resulting in low solid-state fluorescence quantum yields. In recent years, there has been an increasing interest in the use of pyrene units in OLEDs, including oligothiophenes with pyrenyl side groups, [9] bipyrenylbenzene molecules, [10] as well as pyrene-carbazole [11] and pyrene-fluorene systems, [12,13] due to their emissive properties combined with high charge carrier mobility. However, the pyrene derivatives that have been reported so far as efficient blue-emitters for OLED applications still present some degree of aggregation in the solid state. [13] A successful effort in the prevention of aggregation in small molecules was achieved with tetrasubstituted, highly sterically hindered pyrenes, which can emit blue light in solution as well in the solid state and with high quantum yield.[14] The well-known 1,3,6,8-tetraphenylpyrene, for example, has been used in OLEDs, [14] organic field-effect transistors (OFET)s, [15] as well in organic light-emitting field-effect transistors (OLEFET)s. [16] Additional tetrasubstituted systems including different phenyl derivatives [14] or pyridyl units [17] at the 1-, 3-, 6-, and 8-positions have been reported ...

Fullerene derivatives are attractive building blocks for the preparation of molecular and supramolecular photoactive devices. As a part of this research, combination of C60 with oligophenylenevinylene (OPV) subunits has generated significant research efforts. These results are summarized in the present account to illustrate the current state-of-the-art of fullerene chemistry for the development of new photoactive materials.