Am ajor handicap towards the exploitation of radicals is their inherent instability.I nt he paramagnetic azafullerenyl radical C 59 NC,t he unpaired electron is strongly localized next to the nitrogen atom, which induces dimerization to diamagnetic bis(azafullerene), (C 59 N) 2 .C onventional stabilization by introducing steric hindrance around the radical is inapplicable here because of the concave fullerene geometry. Instead, we developed an innovative radical shielding approach based on supramolecular complexation, exploiting the protection offered by a[ 10]cycloparaphenylene ([10]CPP) nanobelt encircling the C 59 NC radical. Photoinduced radical generation is increased by af actor of 300. The EPR signal showing characteristic 14 Nh yperfine splitting of C 59 NC& [10]CPP was traced even after several weeks,w hichc orresponds to alifetime increase of > 10 8 .The proposed approach can be generalized by tuning the diameter of the employed nanobelts,opening new avenues for the design and exploitation of radical fullerenes.
Azobenzene, as one of the most prominent molecular switches, is featured in many applications ranging from photopharmacology to information or energy storage. In order to easily and reproducibly synthesize non-symmetric substituted azobenzenes in an efficient way, especially on a large scale, the commonly used Baeyer–Mills coupling reaction was adopted to a continuous flow setup. The versatility was demonstrated with a scope of 20 substances and the scalability of this method exemplified by the synthesis of >70 g of an azobenzene derivative applied in molecular solar thermal storage (MOST) systems.
Am ajor handicap towards the exploitation of radicals is their inherent instability.I nt he paramagnetic azafullerenyl radical C 59 NC,t he unpaired electron is strongly localized next to the nitrogen atom, which induces dimerization to diamagnetic bis(azafullerene), (C 59 N) 2 .C onventional stabilization by introducing steric hindrance around the radical is inapplicable here because of the concave fullerene geometry. Instead, we developed an innovative radical shielding approach based on supramolecular complexation, exploiting the protection offered by a[ 10]cycloparaphenylene ([10]CPP) nanobelt encircling the C 59 NC radical. Photoinduced radical generation is increased by af actor of 300. The EPR signal showing characteristic 14 Nh yperfine splitting of C 59 NC& [10]CPP was traced even after several weeks,w hichc orresponds to alifetime increase of > 10 8 .The proposed approach can be generalized by tuning the diameter of the employed nanobelts,opening new avenues for the design and exploitation of radical fullerenes.
The preparation of cycloparaphenylenes ([n]CPPs) with their bent π-system poses a long-standing challenge in organic synthesis. In the current multi-step approaches to access CPPs, pre-angulated precursors were combined using transition metal-catalysed or mediated coupling reactions. Therefore, there is a long way to the realisation of the idea of an ‘ideal synthesis’. An easy and efficient synthesis of different [n]CPPs would represent a breakthrough, also pushing their incorporation into organic materials. By combining multiple steps in a one-pot approach, the overall time and workload can be drastically shortened. Herein, we present the application of this concept for the preparation of [6] and [9]CPP as a simple and fast alternative to current methods. By tuning the reaction conditions the selective synthesis of both [6] and [9]CPP was demonstrated.
The synthesis of [n]cycloparaphenylenes ([n]CPPs) and similar nanohoops is usually based on the combination of building blocks to a macrocyclic precursor, which is then aromatized in the final step. Access to those building blocks in large amounts will simplify the synthesis and studies of CPPs as novel functional materials in applications. Herein, we report a continuous flow synthesis of key CPP building blocks using versatile synthesis techniques such as electrochemical oxidation, lithiations and Suzuki cross couplings in self‐built reactors on up‐to kilogram scale.
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