Max Martin

Polycyclic heteroaromatic compounds including pyrrole units are promising functional scaffolds owing to their electron-rich nature, bright fluorescence, and applicability to anion recognition at the pyrrolic hydrogen. We report herein the effective synthesis of pseudo-aza[5]helicene and aza[7]helicene derivatives, and unexpected formation of azahepta[8]circulenes by oxidative fusion reactions. By choosing reaction conditions and peripheral substituents attached at the terminal indole moieties, we obtained aza[7]helicenes 10a-c and azahepta[8]circulenes 11a,c selectively in moderate to good yields. Their solid-state structures have been revealed by X-ray diffraction analysis. UV/Vis absorption, emission, and cyclic voltammetry of these compounds were studied in comparison with those of previously reported tetraaza[8]circulene (TA8C), a symmetric and planar molecule. Furthermore, the enantiomeric separation of dimethyl-substituted aza[7]helicene 10b was achieved, and the racemization kinetics have been elucidated both theoretically and experimentally. This work illustrates a wealth of advantages of pyrrole incorporation into the polycyclic aromatic scaffolds in terms of synthetic aspects, structural variation and optical tuning.

Herein, we report on the synthesis of a novel π-extended "superhelicene" based on hexa-peri-hexabenzocoronenes (HBC) via an efficient four-step synthetic procedure starting from diphenylether. Comprehensive structural analyses were performed by means of NMR and mass spectrometry measurements together with X-ray analysis. Physico-chemical analysis of the superhelicene and suitable HBC references revealed among others outstanding fluorescent features with quantum yields of over 80%.

The design of a novel concept for the synthesis of [3:2] pentakisadducts of fullerene C60 is presented. A sequential tether-directed remote functionalization approach is introduced for the construction of pentakisadducts. This fullerene derivative embellished with two different addends in two different directions can be considered as a valuable tecton for further functionalization. The stepwise cyclopropanation of C60 with a macrocyclic trismalonate and a bis(β-ketoester) yielded the corresponding pentakisadduct with an incomplete octahedral addition pattern. The reaction sequence gave access to two pairs of enantiomers that were easily separated by column chromatography on achiral stationary phase and characterized.