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 complex of [10]cycloparaphenylene ([10]CPP) with bis(azafullerene) (C N) is investigated experimentally and computationally. Two [10]CPP rings are bound to the dimeric azafullerene giving [10]CPP⊃(C N) ⊂[10]CPP. Photophysical and redox properties support an electronic interaction between the components especially when the second [10]CPP is bound. Unlike [10]CPP⊃C , in which there is negligible electronic communication between the two species, upon photoexcitation a partial charge transfer phenomenon is revealed between [10]CPP and (C N) reminiscent of CPP-encapsulated metallofullerenes. Such an alternative electron-rich fullerene species demonstrates C -like ground-state properties and metallofullerene-like excited-state properties opening new avenues for construction of functional supramolecular architectures with organic materials.
Stable and abundant spin-1/2 species from azafullerene (C59N˙) supramolecularly hosted in [10]cycloparaphenylene nanohoops are operated as stable qubits, with possibility of qubit wiring via intermediate polymerized spin-redistributed states.
Double-walled carbon nanotubes (DWCNTs) are fluorinated using (1) fluorine F2 at 200 °C, (2) gaseous BrF3 at room temperature, and (3) CF4 radio-frequency plasma functionalization. These have been comparatively studied using transmission electron microscopy and infrared, Raman, X-ray photoelectron, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A formation of covalent C–F bonds and a considerable reduction in the intensity of radial breathing modes from the outer shells of DWCNTs are observed for all samples. Differences in the electronic state of fluorine and the C–F vibrations for three kinds of the fluorinated DWCNTs are attributed to distinct local surroundings of the attached fluorine atoms. Possible fluorine patterns realized through a certain fluorination technique are revealed from comparison of experimental NEXAFS F K-edge spectra with quantum-chemical calculations of various models. It is proposed that fluorination with F2 and BrF3 produces small fully fluorinated areas and short fluorinated chains, respectively, while the treatment with CF4 plasma results in various attached species, including single or paired fluorine atoms and –CF3 groups. The results demonstrate a possibility of different patterning of carbon surfaces through choosing the fluorination method.
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