Synthesis of a Möbius carbon nanobelt

Abstract

New technologies for the creation of topological carbon nanostructures have significantly advanced synthetic organic chemistry and materials science. While simple molecular nanocarbons with a belt topology have been constructed recently, analogous carbon nanobelts with a twist, i.e., Möbius carbon nanobelts (MCNBs), have not yet been synthesized due to their high intrinsic strain. Herein, we report the synthesis, isolation, and characterization of a MCNB. Calculations of strain energies suggested that large MCNBs are synthetically accessible. Designing a macrocyclic precursor with an odd number of repeat units led to a successful rational synthetic route via Z-selective Wittig reactions and nickel-mediated intramolecular homocoupling reactions, which yielded (25,25)MCNB over 14 steps. NMR and theoretical calculations revealed that the twist moiety of the Möbius band moves quickly around the MCNB molecule in solution. The topological chirality originating from the Möbius structure was confirmed experimentally using chiral HPLC separation and CD spectroscopy.

Non-intersecting ring currents in [12]infinitene

“…[12]Infinitene does not obey the Mo ¨bius and Hu ¨ckel aromaticity rules, since it is not an annulene but a polyarylene with two nearly independent ring-current pathways suggesting that 4n p electrons lead to aromaticity. The aromaticity of new twisted structures [47][48][49] must be addressed carefully, taking into consideration the magnetic response properties, since counting the number of p electrons in the delocalization pathway may lead to incorrect conclusions concerning their aromatic character. 1 Ring-current strengths (in nA/T) of (P,P)-infinitene (neutral and dication) divided into their diatropic and paratropic components calculated at the CAM-B3LYP/def2-TZVP level when the external field points parallel to z axis.…”