Conjugated aromatic systems

The synthesis of conjugated aromatic molecules and polymers with tailored properties provides a useful range of materials for electronic devices.

Renana Gershoni-Poranne, Branco Weiss fellow and assistant professor at the Technion - Israel Institute of Technology, talks to Nature Synthesis about probing aromatic molecules with computational tools.

Birgit Esser, Full Professor of Organic Chemistry at Ulm University, talks to Nature Synthesis about the challenges of synthesizing conjugated nanohoops and other aromatic systems.

Aromatic molecules with multiple one-half twists are synthesized using different precursors and synthetic routes. The pseudo-helicoidal structural chirality of these molecules and the loop of the twisted π-electronic structure fully overlap, thus giving rise to enhanced chiroptical responses.

The synthesis of polyacene is hampered by low solubility and instability of the product as well as side reactions. Now, polyacene is synthesized by polymerizing monomers confined in a metal–organic framework.

The synthesis of topological molecular carbons with persistent chirality is challenging. Here, a triply twisted Möbius carbon nanobelt was synthesized and its two enantiomers were isolated, showing a large absorption dissymmetry factor.

Twisted aromatic belts provide unique topologies and complex chiralities for nanocarbon materials. Now, rhodium-catalysed asymmetric [2 + 2 + 2] cycloadditions enable the stereoselective synthesis of doubly, triply and quadruply twisted aromatic belts.

Elongation of acenes with linearly fused benzene rings is a synthetic challenge. Now, the use of a metal–organic framework enables the synthesis of polymeric precursors, which undergo thermal transformation to form polyacenes.

Graphene-like molecules with a zigzag periphery are synthetically challenging. Now, a programmable zigzag π-extension strategy to rapidly assemble graphene-like molecules is reported based on rhodium-catalysed sequential C2–H and C8–H activation-annulation of naphthalene ketones, using acetylenedicarboxylates as the C2 insertion unit.

Atomically precise graphene fragments are synthesized by using a radical-mediated coupling approach. One open-shell doublet graphene fragment forms a persistent bilayer assembly with highly delocalized 32-centre-2-electron pancake bonding.

Strategies for the creation of topological carbon nanostructures have greatly advanced synthetic organic chemistry and materials science. Now, the synthesis of a Möbius carbon nanobelt, a molecule with a twist on belt-shaped aromatic hydrocarbons, is reported.

Using a bottom-up synthetic method, an all sp²-hybridized carbon nanobelt with a Möbius topology is prepared. The macrocyclization step is a Wittig reaction between an aldehyde and phosphorous ylide at opposite edges of a strip that induces a twist.