A Long‐Lived Azafullerenyl Radical Stabilized by Supramolecular Shielding with a [10]Cycloparaphenylene

Akaike's Information Criterion for Stoichiometry Inference of Supramolecular Complexes

"How do we decide the stoichiometry of host-guest complexes?" This question has long been answered by the Job plot since its first report in 1928. However, as the Job plot was claimed to be misleading in 2016, the question became an open question again and called for renewed investigations. An information-theoretic approach, called Akaike's information criterion, is introduced in this study to select the best model of host-guest complexes, which can rank the models with weight of evidence. A few test cases with unique cylindrical hosts were examined to demonstrate the applicability of the information-theoretic method. Consequently, reasonable views over the thermodynamic behaviors of dumbbell-and-cylinder complexes were obtained. Akaike's information criterion can be a useful and superior alternative to statistical null hypothesis testing, which was proposed as a remedy in place of the Job plot.

Two Rings Around One Ball: Stability and Charge Localization of [1 : 1] and [2 : 1] Complex Ions of [10]CPP and C60/70 [ *]

We investigate the gas-phase chemistry of noncovalent complexes of [10]cycloparaphenylene ([10]CPP) with C₆₀ and C₇₀ by means of atmospheric pressure photoionization and electrospray ionization mass spectrometry. The literature-known [1 : 1] complexes, namely [10]CPP⊃C₆₀ and [10]CPP⊃C₇₀ , are observed as radical cations and anions. Their stability and charge distribution are studied using energy-resolved collision-induced dissociation (ER-CID). These measurements reveal that complexes with a C₇₀ core exhibit a greater stability and, on the other hand, that the radical cations are more stable than the respective radical anions. Regarding the charge distribution, in anionic complexes charges are exclusively located on C₆₀ or C₇₀ , while the charges reside on [10]CPP in the case of cationic complexes. [2 : 1] complexes of the ([10]CPP₂ ⊃C_60/70 )⁺ ⋅^/- ⋅ type are observed for the first time as isolated solitary gas-phase species. Here, C₆₀ -based [2 : 1] complexes are less stable than the respective C₇₀ analogues. By virtue of the high stability of cationic [1 : 1] complexes, [2 : 1] complexes show a strongly reduced stability of the radical cations. DFT analyses of the minimum geometries as well as molecular dynamics calculations support the experimental data. Furthermore, our novel gas-phase [2 : 1] complexes are also found in 1,2-dichlorobenzene. Insights into the thermodynamic parameters of the binding process as well as the species distribution are derived from isothermal titration calorimetry (ITC) measurements.

A Metallofullertube of Ce2 @C100 with a Carbon Nanotube Segment: Synthesis, Single-Molecule Conductance and Supramolecular Assembly

Tubular fullerenes can be considered as end-capped carbon nanotubes with accurate structure, which are promising nanocarbon materials for advanced single-molecule electronic devices. Herein, we report the synthesis and characterization of a metallofullertube Ce₂ @D₅ (450)-C₁₀₀ , which has a tubular C₁₀₀ cage with a carbon nanotube segment and two fullerene end-caps. As there are structure correlations between tubular Ce₂ @D₅ (450)-C₁₀₀ and spherical Ce₂ @I_h -C₈₀ , their structure-property relationship has been compared by means of experimental and theoretical methods. Notably, single-molecule conductance measurement determined that the conductivity of Ce₂ @D₅ (450)-C₁₀₀ was up to eight times larger than that of Ce₂ @I_h -C₈₀ . Furthermore, supramolecular assembly of Ce₂ @D₅ (450)-C₁₀₀ and a [12]CPP nanohoop was investigated, and theoretical calculations revealed that metallofullertube Ce₂ @D₅ (450)-C₁₀₀ adopted a "standing" configuration in the cavity of [12]CPP. These results demonstrate the special nature of this kind of metallofullertube.

First Synthesis of the Inherently Chiral Trans-4' Bisadduct of C59 N Azafullerene by Using Cyclo-[2]-dodecylmalonate as a Tether

The multiaddition chemistry of azafullerene C₅₉ N has been scarcely explored, and the isolation of pure bisadducts is in its infancy. Encouraged by the recent regioselective synthesis of the inherently chiral equatorial_face bisadduct of C₅₉ N, we focused on the isolation of the first trans-4 bisadduct in a simple two-step approach. The first regioselective synthesis of the trans-4 bisadduct of C₅₉ N by using cyclo-[2]-dodecylmalonate as a tether is now reported. The newly synthesized bisadduct has C₁ symmetry, as evidenced by ¹³ C NMR, while X-ray crystallography validated the trans-4' addition pattern. Furthermore, the inherently chiral trans-4' C₅₉ N bisadduct was enantiomerically resolved, and the mirror-image relation of the two enantiomers was probed by circular dichroism spectroscopy. Finally, UV-Vis and redox assays suggested that the addition pattern has a reflection in the light-harvesting and redox properties of the bisadduct.