Regioselective CF 2 functionalization of Sc 3 N@ D 3h (5)-C 78 Pykhova, Anastasia D; Semivrazhskaya, Olesya O; Samoylova, Nataliya A ...
Dalton transactions : an international journal of inorganic chemistry,
2022-Jan-17, 2022-01-17, Volume:
51, Issue:
3
Journal Article
Peer reviewed
We report the first synthesis and computational study of Sc
N@C
(CF
) - an analog of the previously reported Sc
N@C
(CF
) with a less common carbon cage whose chemical properties presently remain far ...less studied. Sc
N@C
appears to be considerably more reactive toward CF
addition than Sc
N@C
and somewhat more reactive than C
. Even though the less symmetric
(5)-C
carbon cage offers far broader opportunities for isomerism than
-C
, CF
addition to Sc
N@C
proceeds regioselectively, similarly to other common fullerene reactions. A DFT survey of the thermodynamic and kinetic aspects of CF
addition demonstrates that the regioselectivity is controlled kinetically.
Halogenated buckybowls or bowl‐shaped polycyclic aromatic hydrocarbons (BS‐PAHs) are key building blocks for the “bottom‐up” synthesis of various carbon‐based nanomaterials with outstanding potential ...in different fields of technology. The current state of the art provides quite a limited number of synthetic pathways to BS‐PAHs; moreover, none of these approaches show high selectivity and tolerance of functional groups. Herein we demonstrate an effective route to BS‐PAHs that includes directed intramolecular aryl–aryl coupling through C−F bond activation. The coupling conditions were found to be completely tolerant toward aromatic C−Br and C−Cl bonds, thus allowing the facile synthesis of rationally halogenated buckybowls with an unprecedented level of selectivity. This finding opens the way to functionalized BS‐PAH systems that cannot be obtained by alternative methods.
Efficiency that will bowl you over: The activation of aromatic C−F bonds in the presence of more labile C−Br and C−Cl bonds enabled the fully controlled synthesis of halogenated bowl‐shaped polycyclic aromatic hydrocarbons through intramolecular aryl–aryl coupling (see picture). Besides its simplicity and high reproducibility, the technique provides access to halogenated bowl‐shaped systems that are not accessible by other methods.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Two novel derivatives of the C
fullerene with 9- and 10-membered cage openings were obtained by means of oxidation and decarbonylation of C
(CF
)
. The major product, C
(O)(CF
)
O
, features a ...cleaved C-C bond transformed into two carbonyl functions plus an ether bridge. The second product, C
O(CF
)
O, has one of the carbonyls replaced with another ether bridge. We provide a DFT analysis of the possible formation pathways to give the oxidized compounds under the action of pyridine
-oxide.
Two novel derivatives of the C70 fullerene with 9- and 10-membered cage openings were obtained by means of oxidation and decarbonylation of C70(CF3)8. The major product, C70(O)(CF3)8O2, features a ...cleaved C–C bond transformed into two carbonyl functions plus an ether bridge. The second product, C69O(CF3)8O, has one of the carbonyls replaced with another ether bridge. We provide a DFT analysis of the possible formation pathways to give the oxidized compounds under the action of pyridine N-oxide.
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•Rapid ultrasound-probe preparation of aqueous fullerene dispersions (AFDs).•Sonication probe is more effective for AFD preparation than a bath.•AFDs have up to 80 ppm concentrations, ...180 nm mean diameter, –32 mV ζ-potential.•AFDs of C60, C70, Gd@C82, etc. showed long-term storage and aggregate stability.•Complete characterization and metal/organic impurities control of AFDs is proposed.
A green, scalable, and sustainable approach to prepare aqueous fullerene dispersions (AFD) C60, C70, endohedral metallofullerene Gd@C82, and their derivatives C60Cl6, C70Cl10, and supramolecular and ester-like derivatives, 10 fullerene species total, is proposed. For the first time, an immersed ultrasonic probe was used to preparing dispersions for pristine fullerenes without addends. Both ultrasound-assisted solvent-exchange and direct sonication techniques for AFD preparation using an immersed probe were tested. The average time for AFD preparation decreases 10–15 times compared to an ultrasound-bath-assisted technique, while final fullerene concentrations in AFDs remained at tens of ppm (up to 80 ppm). The aqueous dispersions showed long-term stability, a negatively charged surface with a zeta potential up to –32 mV with an average nanocluster diameter of no more than 180 nm. The total anionic and cationic compositions of samples were found by inductively coupled plasma atomic emission spectroscopy and chromatographic techniques. The highlights and challenges of using an ultrasound probe for AFD production are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Addition of CF2 group to endohedral fullerene Sc3N@Ih-C80 Pykhova, Anastasia D; Semivrazhskaya, Olesya O; Samoylova, Nataliya A ...
Dalton transactions : an international journal of inorganic chemistry,
07/2020, Volume:
49, Issue:
26
Journal Article
Peer reviewed
We report the first successful synthesis of a CF2 derivative of the stable endohedral fullerene Sc3N@Ih-C80. Reaction with CF2ClCOONa yields a single Cs-symmetric Sc3N@C80(CF2) adduct where the CF2 ...group is inserted into a 6,6-bond and opens it to 2.3 Å between the bridgehead carbon atoms. As evidenced by absorption and fluorescence spectroscopy as well as cyclic voltammetry, both the HOMO and the LUMO level of Sc3N@C80(CF2) are slightly (ca. 0.1 eV) downshifted with respect to the parent Sc3N@Ih-C80, so the HOMO–LUMO gap remains essentially unchanged. The DFT calculations suggest that the reaction mechanism is not the previously assumed 2 + 1-cycloaddition of :CF2 carbene but rather nucleophilic addition of CF2Cl− anion followed by elimination of Cl− and closing of the CF2 bridge via intramolecular nucleophilic substitution. Selective formation of the 6,6-Sc3N@C80(CF2) turns out to be kinetically controlled and promoted by a particular orientation of the endohedral Sc3N cluster with respect to the CF2Cl− addition site. In its turn, the CF2 addend partly hampers the rotation of Sc3N the endohedral cluster compared to its quasi-free reorientations in the parent Sc3N@Ih-C80.
We report synthesis, isolation, and spectroscopic characterization of the novel 5,6-open C70(CF2) isomer III along with the already known 6,6-closed and 6,6-open C70(CF2) isomers I and II. The ...compounds were obtained in a ratio of I : II : III = 4 : 6 : 1 by means of thermal treatment of C70 fullerene with sodium chlorodifluoroacetate. This product composition is explained with the use of quantum chemical calculations that identify the reaction pathway as a two-stage nucleophilic cyclopropanation rather than the previously postulated carbene addition. We further report the first cyclic voltametric studies for the whole set of isomers of C70(CF2). Together with the DFT data, they demonstrate that the LUMO is stabilized in both isomer II (6,6-open) and III (5,6-open) by 0.1 eV with respect to the pristine C70, and isomer III has the lowest reorganization energy of all.
We propose a simple and dry technique to functionalize and dope single-walled carbon nanotubes (SWCNTs) with ozone. The doping under ozone-controlled conditions (300 mg/h) during 30 min was shown to ...give a 4-fold decrease in the sheet resistance of SWCNT films (148 Ω/square at the transmittance of 90%). Further ozone treatment of the SWCNTs leads to deterioration in the film conductance. The conductivity alteration is discussed in the light of the Criegee mechanism, oxidation and charge transfer during the ozone exposure. The samples were characterized by TEM, FT-IR, Raman, UV–vis–NIR, and XPS to confirm the findings of the work. The ozone-treated samples show increased hydrophilicity with increasing ozone treatment time, which makes possible to coat the SWCNT samples with inorganic materials. SWCNTs after ozone treatment can be successfully and uniformly coated by ZnO with the help of atomic layer deposition (ALD) technique.
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Gas phase molecules of hexachlorobenzene (C6Cl6) were investigated by means of dissociative electron attachment spectroscopy (DEAS). Three channels of molecular negative ions decay have been ...identified: ion of Cl− and Cl2− as well as electron detachment (τa∼250 μs at 343 K). All three channels exhibit temperature dependence. The adiabatic electron affinity estimated using a simple but typically accurate Arrhenius model (EAa=1.6–1.9 eV) turns out to be much higher than the quantum‐chemical predictions (EAa=0.9–1.0 eV). We discuss the possible reasons behind the observed discrepancy.
Gas‐phase electron capture by hexachlorobenzene molecules was investigated by means of DEA spectroscopy. Hexachlorobenzene anions demonstrate three principal decay channels: ion of Cl− or Cl2− and electron autodetachment. The adiabatic electron affinity of C6Cl6, estimated from the autodetachment kinetics according to a simple yet typically accurate Arrhenius model, turns out to be much higher than the commonly accepted value of about 1.0 eV. This unexpected discrepancy is rationalized in terms of involvement of an intermediate metastable anionic state.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In recent years, many higher fullerenes that obey the isolated pentagon rule (IPR) were found capable of rearranging into molecules with adjacent pentagons and even with heptagons via ...chlorination-promoted skeletal transformations. However, the key fullerene, buckminsterfullerene I
-C
, long seemed insusceptible to such rearrangements. Now we demonstrate that buckminsterfullerene yet can be transformed by chlorination with SbCl
at 420-440 °C and report X-ray structures for the thus-obtained library of non-IPR derivatives. The most remarkable of them are non-IPR C
Cl
and C
Cl
with fundamentally rearranged carbon skeletons featuring, respectively, four and five fused pentagon pairs (FPPs). Further high-temperature trifluoromethylation of the chlorinated mixture afforded additional non-IPR derivatives C
(CF
)
and C
(CF
)
, both with two FPPs, and a nonclassical C
(CF
)
F with a heptagon, two FPPs, and a fully fused pentagon triple. We discuss the general features of the addition patterns in the new non-IPR compounds and probable pathways of their formation via successive Stone-Wales rearrangements.
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