Unexpected Disparity in Photoinduced Reactions of C60 and C70 in Water with the Generation of O2•– or 1O2
Ontology highlight
ABSTRACT:
SUBMITTER: Liosi K
PROVIDER: S-EPMC8549049 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Ionic complexes between gold and C60 have been observed for the first time. Cations and anions of the type [Au(C60)2]+/- are shown to have particular stability. Calculations suggest that these ions adopt a C60-Au-C60 sandwich-like (dumbbell) structure, which is reminiscent of [XAuX]+/- ions previously observed for much smaller ligands. The [Au(C60)2]+/- ions can be regarded as Au(I) complexes, regardless of whether the net charge is positive or negative, but in both cases, the charge transfer between the Au and C60 is incomplete, most likely because of a covalent contribution to the Au-C60 binding. The C60-Au-C60 dumbbell structure represents a new architecture in fullerene chemistry that might be replicable in synthetic nanostructures.
| S-EPMC5964450 | biostudies-literature
Project description:An open-cage fullerene incorporating phosphorous ylid and carbonyl group moieties on the rim of the orifice can be filled with gases (H2 , He, Ne) in the solid state, and the cage opening then contracted in situ by raising the temperature to complete an intramolecular Wittig reaction, trapping the atom or molecule inside. Known transformations complete conversion of the product fullerene to C60 containing the endohedral species. As well as providing an improved synthesis of large quantities of 4 He@C60 , H2 @C60 , and D2 @C60 , the method allows the efficient incorporation of expensive gases such as HD and 3 He, to prepare HD@C60 and 3 He@C60 . The method also enables the first synthesis of Ne@C60 by molecular surgery, and its characterization by crystallography and 13 C NMR spectroscopy.
| S-EPMC8048630 | biostudies-literature
Project description:The antioxidant potential (capacity and activity) of aqueous fullerene dispersions (AFD) of non-functionalized C60, C70, and Gd@C82 endofullerene (in micromolar concentration range) was estimated based on chemiluminescence measurements of the model of luminol and generation of organic radicals by 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP). The antioxidant capacity was estimated by the TRAP method, from the concentration of half-suppression, and from the suppression area in the initial period. All three approaches agree and show that the antioxidant capacity of AFDs increased in the order Gd@C82 < C70 < C60. Mathematical modeling of the long-term kinetics data was used for antioxidant activity estimation. The effect of C60 and C70 is found to be quenching of the excited product of luminol with ABAP-generated radical and not an actual antioxidant effect; quenching constants differ insignificantly. Apart from quenching with a similar constant, the AFD of Gd@C82 exhibits actual antioxidant action. The antioxidant activity in Gd@C82 is 300-fold higher than quenching constants.
| S-EPMC8199091 | biostudies-literature
Project description:We report the first synthesis of 225Ac (t 1/2 = 10 days) endohedral fullerenes,225Ac@C60. The 225Ac@C60 was produced with a 12 ± 2% efficiency by applying an electrical arc discharge between a source of α-particle emitter 225Ac (∼1 mCi, electroplated on a Pt disk) and a thin coat of "preformed" C60 on an Al disk (C60 thickness of ∼0.25 mg/cm2). After formation by electrical arc discharge, the resulting radiofullerenes on the Al disk were dissolved in toluene under anaerobic conditions and converted to a malonate derivative using the Bingel reaction. Subsequent to repeated washings of the organic phase with dilute acidic solutions to remove exohedral 225Ac, ∼45% of 225Ac activity was retained in the organic phase, which resisted extraction into the aqueous phase. Failure to extract the 225Ac from the organic phase provided definitive evidence that the 225Ac is located inside of the fullerene. The formation of 225Ac@C60 was further confirmed using a classical hot-atom chemistry technique in which the organic phase containing purified endohedral 225Ac@C60 malonate was contacted with fresh dilute acid to repeatedly extract the ionic 4.8 m 221Fr and 45.6 m 213Bi activities (decay daughters of 225Ac), which were released by molecular disruption due to nuclear recoil. The result from the extraction experiments was further supported by a series of thin-layer chromatography and high-pressure liquid chromatography analysis of the organic phase containing 225Ac@C60 or 225Ac@C60 malonate. Taken together, studies show that, like polydentate chelators, single-wall fullerenes are not capable of retaining the 225Ac decay daughters.
| S-EPMC7594009 | biostudies-literature
Project description:Helium is considered an almost ideal tagging atom for cold messenger spectroscopy experiments. Although helium is bound very weakly to the ionic molecule of interest, helium tags can lead to shifts and broadenings that we recorded near 963.5 nm in the electronic excitation spectrum of C60+ solvated with up to 100 helium atoms. Dedicated quantum calculations indicate that the inhomogeneous broadening is due to different binding energies of helium to the pentagonal and hexagonal faces of C60+, their dependence on the electronic state, and the numerous isomeric structures that become available for intermediate coverage. Similar isomeric effects can be expected for optical spectra of most larger molecules surrounded by nonabsorbing weakly bound solvent molecules, a situation encountered in many messenger-tagging spectroscopy experiments.
| S-EPMC5857924 | biostudies-literature
Project description:The donor-acceptor ability of frustrated Lewis pairs (FLPs) has led to widespread applications in organic synthesis. Single electron transfer from a donor Lewis base to an acceptor Lewis acid can generate a frustrated radical pair (FRP) depending on the substrate and energy required (thermal or photochemical) to promote an FLP into an FRP system. Herein, we report the Csp3-Csp cross-coupling reaction of aryl esters with terminal alkynes using the B(C6F5)3/Mes3P FLP. Significantly, when the 1-ethynyl-4-vinylbenzene substrate was employed, the exclusive formation of Csp3-Csp cross-coupled products was observed. However, when 1-ethynyl-2-vinylbenzene was employed, solvent-dependent site-selective Csp3-Csp or Csp3-Csp2 cross-coupling resulted. The nature of these reaction pathways and their selectivity has been investigated by extensive electron paramagnetic resonance (EPR) studies, kinetic studies, and density functional theory (DFT) calculations both to elucidate the mechanism of these coupling reactions and to explain the solvent-dependent site selectivity.
| S-EPMC8041292 | biostudies-literature
Project description:Aromatic amino acids such as l-tyrosine and l-tryptophan are deployed in natural systems to mediate electron transfer (ET) reactions. While tyrosine oxidation is always coupled to deprotonation (proton-coupled electron-transfer, PCET), both ET-only and PCET pathways can occur in the case of the tryptophan residue. In the present work, two novel conjugates 1 and 2, based on a SnIV tetraphenylporphyrin and SnIV octaethylporphyrin, respectively, as the chromophore/electron acceptor and l-tryptophan as electron/proton donor, have been prepared and thoroughly characterized by a combination of different techniques including single crystal X-ray analysis. The photophysical investigation of 1 and 2 in CH2 Cl2 in the presence of pyrrolidine as a base shows that different quenching mechanisms are operating upon visible-light excitation of the porphyrin component, namely photoinduced electron transfer and concerted proton electron transfer (CPET), depending on the chromophore identity and spin multiplicity of the excited state. The results are compared with those previously described for metal-mediated analogues featuring SnIV porphyrin chromophores and l-tyrosine as the redox active amino acid and well illustrate the peculiar role of l-tryptophan with respect to PCET.
| S-EPMC8252543 | biostudies-literature
Project description:A reliable synthesis of unstable and highly reactive BrO2 F is reported. This compound can be converted into BrO2 + SbF6 - , BrO2 + AsF6 - , and BrO2 + AsF6 - ?2?BrO2 F. The latter decomposes into mixed-valent Br3 O4 ?Br2 + AsF6 - with five-, three-, one-, and zero-valent bromine. BrO2 + H(SO3 CF3 )2 - is formed with HSO3 CF3 . Excess BrO2 F yields mixed-valent Br3 O6 + OSO3 CF3 - with five- and three-valent bromine. Reactions of BrO2 F and MoF5 in SO2 ClF or CH2 ClF result in Cl2 BrO6 + Mo3 O3 F13 - . The reaction of BrO2 F with (CF3 CO)2 O and NO2 produces O2 Br-O-CO-CF3 and the known NO2 + Br(ONO2 )2 - . All of these compounds are thermodynamically unstable.
| S-EPMC6973041 | biostudies-literature
Project description:FeII 4L6 tetrahedral cage 1 was prepared from a redox-active dicationic naphthalenediimide (NDI) ligand. The +20 charge of the cage makes it a good host for anionic guests, with no binding observed for neutral aromatic molecules. Following reduction by Cp2Co, the cage released anionic guests; subsequent oxidation by AgNTf2 led to re-uptake of anions. In its reduced form, however, 1 was observed to bind neutral C60. The fullerene guest was subsequently ejected following cage re-oxidation. The guest release process was found to be facilitated by anion-mediated transport from organic to aqueous solution. Cage 1 thus employs electron transfer as a stimulus to control the uptake and release of both neutral and charged guests, through distinct pathways.
| S-EPMC8146419 | biostudies-literature
Project description:Redox reactions, substitutions, and metalations are reported for the iron carbido sulfide [Fe6C(CO)14(S)]2- ([1]2-). Dianion [1]2- oxidized to [Fe6C(CO)16(S)]0 ([2]0) upon treatment with of [Fe(C5H5)2]BF4 or HBF4 (H2 formation) under an atmosphere of CO. Reaction of [2]0 with tBuNC gave [Fe6C(S)(CO)13(tBuNC)5], consisting of Fe5C(CO)13 and [Fe(tBuNC)5]2+ subunits linked by a μ3-S2-. The Fe7CS cluster [Fe7C(CO)17(S)]2- formed upon treatment of (Ph4P)2[1] with Fe(benzylideneacetone)(CO)3. The Fe7 species is an edge-fused cluster with [Fe6C(CO)10(μ-CO)4] and Fe(CO)3 subunits joined by μ3-S and two Fe-Fe bonds. The analogous reaction using Mo(CO)4(norbornadiene) gave [MoFe6C(CO)18(S)]2-. In this cluster, the Mo center is located in the octahedral subunit. Treatment of [1]2- with SO2 afforded [Fe6C(S)(SO2)(CO)13]2-. This cluster features an Fe6C core decorated with μ3-S and μ2-SO2 ligands. These experiments were undertaken in an effort to connect organometallic clusters to FeMoco.
| S-EPMC8054992 | biostudies-literature