Phenacenes from Diels-Alder trapping of photogenerated o-xylylenols: phenanthrenes and benzo[e]pyrene bisimide.

[structure: see text] The synthesis of phenanthrene and benzo[e]pyrene bisimides, 1 and 2, was accomplished via the Diels-Alder trapping of sterically congested o-xylylenols photochemically generated from 3,6-dibenzoyl-o-xylene and 1,4-dibenzoyl-9,10-dihydroanthracene, respectively. Absorption and emission from 2 are red-shifted from 1 and unsubstituted benzo[e]pyrene. The fluorescence quantum yield for 2 is an order of magnitude lower than that of 1 and comparable to that of the parent benzo[e]pyrene.

Twisted, Z-shaped perylene bisimide.

The first derivative of a new class of perylene bisimide chromophores, N,N'-bis(octyl)-3,9-bis(phenyl)perylene-1,2,7,8-tetracarboxyl bisimide, 1, has been synthesized and its fundamental photophysical and electrochemical properties assessed. The extended, Z-shaped structure was achieved by use of the classic photoenolization of an o-methylbenzophenone analogue, 1,5-dibenzoyl-9,10-dihydroanthracene, and in situ Diels-Alder trapping of the resulting o-xylylenol intermediates with N-octylmaleimide. Subsequent dehydration and aromatization of the resulting bisadduct afforded 1. In dichloromethane, bisimide 1 has an absorption lambdamax at 491 nm (epsilon = 29,600 M-1 cm-1), a fluorescence lambdamax at 517 nm with a high quantum yield (Phi = 0.70), and a single-exponential fluorescence decay (tau = 5.01 ns). Pure crystals of 1 have red emission, suggesting exciplex formation in the solid state. X-ray crystallographic analysis of 1 revealed significant twisting of its perylene core.

Recognition-mediated assembly of nanoparticles into micellar structures with diblock copolymers.

Polystyrene-based diblock copolymers, featuring diaminotriazine functionality on one of the blocks were used to assemble complementary uracil-functionalized nanoparticles into micellar aggregates. The size of these self-assembled aggregates was controlled by block length, as determined in solution (using dynamic light scattering), and in thin films (using transmission electron microscopy).

Thermoreversible Polymerization. Formation of Fullerene-Diene Oligomers and Copolymers.

Diels-Alder reaction of C(60) with bis-anthracene 3 provides linear copolymer 4. This material is stable at room temperature but undergoes reversion to the monomeric species upon heating. This thermal depolymerization process was observed at temperatures above 60 degrees C, with an activation energy of 17.1 kcal/mol. This process can be cycled multiply without degradation of the reactive functionalities. In addition to its thermal properties, this polymer retains the rich redox chemistry of the fulleroids. Electrochemical and EPR studies demonstrate copolymer 4 undergoes multiple reductions without decomposition to monomeric species.