A novel π-extended "superhelicene" based on hexa-peri-hexabenzocoronenes (HBCs) has been synthesized by an efficient four-step synthetic procedure starting from diphenyl ether. Comprehensive structural analysis of the helicene was performed by NMR spectroscopy and mass spectrometry measurements together with X-ray analysis. Physicochemical analysis of the superhelicene and suitable HBC references revealed it had outstanding fluorescent features with quantum yields of over 80 %.
Figure 5. a) Absorbance, b) circular dichroism, c) photoluminescence and d) photoluminescence dissymmetry of neat and annealed (T = 140 8C, 10 minutes) F8BT:oxa[7]H (t = 131 nm, l ex : 475 nm). Further systems are considered in the Supporting Information.
A novel rational synthetic pathway-the "functionalization of para-nitroaniline" (FpNA)-provides substituted hexaarylbenzenes (HABs) with uncommon symmetries that bear up to five different substituents, fully avoiding regioisomeric product distributions during the reactions. 4-Nitroaniline is functionalized by a cascade of electrophilic halogenations, Sandmeyer brominations, and Suzuki cross-coupling reactions, leading to 26 substitution geometries, of which 18 structures are not available by the current established techniques. Furthermore, we demonstrate that this method is applicable to the bulk production of such systems on a multigram scale. Regarding optoelectronic properties, we demonstrate how highly functionalized HABs can show strong luminescent behavior, making these molecules very attractive to organic electronic devices.
We designed as traightforwards ynthetic route towards af ull-fledged family of p-extended helicenes:s uperhelicenes.T hey have two hexa-peri-hexabenzocoronenes (HBCs) in common that are connected via ac entral fivemembered ring. By means of structurally altering this 5membered ring, we realized av ersatile library of molecular building blocks.Not only the superhelicene structure,but also their features are tuned with ease.I n-depth physico-chemical characterizations served as ap roof of concept thereof.T he superhelicene enantiomers were separated, their circular dichroism was measured in preliminary studies and concluded with an enantiomeric assignment. Our work was rounded-off by crystal structure analyses.Mixed stacks of M-and P-isomers led to twisted molecular wires.U sing such stacks,c hargecarrier mobilities were calculated, giving reason to expect outstanding hole transporting properties.
Hexa‐peri‐hexabenzocoronides (HBC) was successfully used as a model system for investigating the complex mechanism of the reductive functionalization of graphene. The well‐defined molecular HBC system enabled deeper insights into the mechanism of the alkylation of reductively activated nanographenes. The separation and complete characterization of alkylation products clearly demonstrate that nanographene functionalization proceeds with exceptionally high regio‐ and stereoselectivities on the HBC scaffold. Experimental and theoretical studies lead to the conclusion that the intact basal graphene plane is chemically inert and addend binding can only take place at either preexisting defects or close to the periphery.
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