Interplay of structural dynamics and electronic effects in an engineered assembly of pentacene in a metal-organic framework.

Charge carrier mobility is an important figure of merit to evaluate organic semiconductor (OSC) materials. In aggregated OSCs, this quantity is determined by inter-chromophoric electronic and vibrational coupling. These key parameters sensitively depend on structural properties, including the density of defects.

Singlet exciton fission in a modified acene with improved stability and high photoluminescence yield.

We report a fully efficient singlet exciton fission material with high ambient chemical stability. 10,21-Bis(triisopropylsilylethynyl)tetrabenzo[a,c,l,n]pentacene (TTBP) combines an acene core with triphenylene wings that protect the formal pentacene from chemical degradation. The electronic energy levels position singlet exciton fission to be endothermic, similar to tetracene despite the triphenylenes.

(Aza)Pentacenes Clipped into a Ring: Stabilization of Large (Aza)Acenes.

A doubly alkylene bridged 6,13-diphenylpentacene and analogously bridged azapentacenes were prepared; they are persistent. The doubly bridged azapentacenes display superior photochemical, oxidative and thermal stabilities compared to azapentacenes protected by bis(TIPS-ethynyl)-substituents-clipping an azaacene into a large ring is a viable complement in stabilization.

2,3-Dihalo- and 2,3,6,7-Tetrahaloanthracenes by Vollhardt Trimerization.

We efficiently synthesized otherwise difficult to obtain 2,3- and 2,3,6,7-halogenated anthracenes with diverse east/west substituents. Key steps involve the (i) Vollhardt cyclization of bis(propargyl)benzenes with bis(trimethylsilyl)acetylene, (ii) halo-desilylation introducing chlorine, bromine, or iodine substituents, and (iii) dehydrogenation. Pd catalysis allows selective functionalization at the anthracenes' east/west positions.

Azaacenes Bearing Five-Membered Rings.

We report the synthesis of processible (dihydro)pyracyclene- and acenaphthylene-substituted azaacenes using condensation reactions in solution. The targets are characterized via cyclic voltammetry, X-ray crystallography, UV/Vis, fluorescence spectroscopy and DFT/NICS calculations. Formal hydrogenation of the annulated five-membered ring surprisingly alters emission in the solid-state as a consequence of modulation of aromaticity and HOMO-LUMO overlap.

Dibenzobarrelene-Based Azaacenes: Emitters in Organic Light-Emitting Diodes.

The synthesis of soluble dibenzobarrelene-substituted azaacenes either by condensation reactions in solution or, more effectively, in the solid state by using a ball mill is reported herein. We relate their optical properties in thin films to their packing in the solid state. The targets are characterized by cyclic voltammetry, X-ray crystallography and UV/Vis and fluorescence analysis.