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2.
Chem Commun (Camb) ; 56(27): 3867-3870, 2020 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-32134078

RESUMO

A mixed actinide-lanthanide cluster fullerene, Sc2UC@Ih(7)-C80, was isolated and fully characterized. For the first time, the single crystal X-ray crystallographic analysis confirms a novel actinide-lanthanide cluster Sc2UC stabilized inside an Ih(7)-C80 cage. Moreover, the U[double bond, length as m-dash]C double bond distance is 2.01 Å, the shortest U[double bond, length as m-dash]C bond confirmed by crystallography so far.

3.
J Am Chem Soc ; 141(51): 20249-20260, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31793304

RESUMO

Novel actinide cluster fullerenes, U2C2@Ih(7)-C80 and U2C2@D3h(5)-C78, were synthesized and fully characterized by mass spectrometry, single-crystal X-ray crystallography, UV-vis-NIR, nuclear magnetic resonance spectroscopy (NMR), X-ray absorption spectroscopy (XAS), Raman spectroscopy, IR spectroscopy, as well as density functional and multireference wave function calculations. The encapsulated U2C2 is the first example of a uranium carbide cluster featuring two U centers bridged by a C≡C unit. The U-C bond distances in these U2C2 clusters are in the range between 2.130 and 2.421 Å. While the U2C2 cluster in U2C2@C80 adopts a butterfly-shaped geometry with a U-C2-U dihedral angle of 112.7° and a U-U distance of 3.855 Å, the U-U distance in U2C2@C78 is 4.164 Å and the resulting U-C2-U dihedral angle is increased to 149.1°. The combined experimental and quantum-chemical results suggest that the formal U oxidation state is +4 in the U2C2 cluster, and each U center transfers three electrons to the C2n cage and one electron to C2. Different from the strong U═C covalent bonding reported for U2C@C80, the U-C bonds in U2C2 are less covalent and predominantly ionic. The C-C triple bond is somewhat weaker than in HCCH, and the C-C π bonds undergo donation bonding with the U centers. This work demonstrates that the combination of the unique encapsulation effect of fullerene cages and the variable oxidation states of actinide elements can lead to the stabilization of novel actinide clusters, which are not accessible by conventional synthetic methods.

4.
Inorg Chem ; 58(24): 16722-16726, 2019 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-31773950

RESUMO

For the first time, Th@Td(19151)-C76, a highly symmetric C76 cage encapsulating an actinide metal ion, has been synthesized and characterized by single-crystal X-ray crystallography, mass spectrometry, UV-vis-NIR spectroscopy, and cyclic voltammetry. The single-crystal crystallographic analysis unambiguously assigned the fullerene cage as Td(19151)-C76 and confirmed Th@Td(19151)-C76 as the first IPR (isolated-pentagon rule) C76-based monometallofullerene. The crystallographic results further revealed that the optimal Th site resides over a sumanene-type hexagon, similar to that of the Th@C1(11)-C86 but different from the previously reported Th@C3v(8)-C82. In addition, electrochemical study found that Th@Td(19151)-C76 processes an unusually low first oxidation potential (0.03 V), suggesting its strong electron donating ability.

5.
Adv Sci (Weinh) ; 6(20): 1901352, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31637168

RESUMO

A new class of single-molecule magnets (SMMs) based on Dy-oxide clusterfullerenes is synthesized. Three isomers of Dy2O@C82 with C s(6), C 3v(8), and C 2v(9) cage symmetries are characterized by single-crystal X-ray diffraction, which shows that the endohedral Dy-(µ2-O)-Dy cluster has bent shape with very short Dy-O bonds. Dy2O@C82 isomers show SMM behavior with broad magnetic hysteresis, but the temperature and magnetization relaxation depend strongly on the fullerene cage. The short Dy-O distances and the large negative charge of the oxide ion in Dy2O@C82 result in the very strong magnetic anisotropy of Dy ions. Their magnetic moments are aligned along the Dy-O bonds and are antiferromagnetically (AFM) coupled. At low temperatures, relaxation of magnetization in Dy2O@C82 proceeds via the ferromagnetically (FM)-coupled excited state, giving Arrhenius behavior with the effective barriers equal to the AFM-FM energy difference. The AFM-FM energy differences of 5.4-12.9 cm-1 in Dy2O@C82 are considerably larger than in SMMs with {Dy2O2} bridges, and the Dy∙∙∙Dy exchange coupling in Dy2O@C82 is the strongest among all dinuclear Dy SMMs with diamagnetic bridges. Dy-oxide clusterfullerenes provide a playground for the further tuning of molecular magnetism via variation of the size and shape of the fullerene cage.

6.
Chem Commun (Camb) ; 55(63): 9271-9274, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31298675

RESUMO

A novel actinide endohedral fullerene with an unexpected chiral cage, Th@C1(11)-C86, was synthesized and characterized. DFT calculations suggest that this low symmetry cage was favoured as a consequence of the strong interaction between Th and the cage, which makes the predictions by the ionic model less reliable for these endohedral mono-metallofullerenes.

7.
J Am Chem Soc ; 140(51): 18039-18050, 2018 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-30453733

RESUMO

For the first time, actinide endohedral metallofullerenes (EMFs) with non-isolated-pentagon-rule (non-IPR) carbon cages, U@C80, Th@C80, and U@C76, have been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffractometry, UV-vis-NIR and Raman spectroscopy, and cyclic voltammetry. Crystallographic analysis revealed that the U@C80 and Th@C80 share the same non-IPR cage of C1(28324)-C80, and U@C76 was assigned to non-IPR U@ C1(17418)-C76. All of these cages are chiral and have never been reported before. Further structural analyses show that enantiomers of C1(17418)-C76 and C1(28324)-C80 share a significant continuous portion of the cage and are topologically connected by only two C2 insertions. DFT calculations show that the stabilization of these unique non-IPR fullerenes originates from a four-electron transfer, a significant degree of covalency, and the resulting strong host-guest interactions between the actinide ions and the fullerene cages. Moreover, because the actinide ion displays high mobility within the fullerene, both the symmetry of the carbon cage and the possibility of forming chiral fullerenes play important roles to determine the isomer abundances at temperatures of fullerene formation. This study provides what is probably one of the most complete examples in which carbon cage selection occurs through thermodynamic control at high temperatures, so the selected cages do not necessarily coincide with the most stable ones at room temperature. This work also demonstrated that the metal-cage interactions in actinide EMFs show remarkable differences from those previously known for lanthanide EMFs. These unique interactions not only could stabilize new carbon cage structures, but more importantly, they lead to a new family of metallofullerenes for which the cage selection pattern is different to that observed so far for nonactinide EMFs. For this new family, the simple ionic A q+@C2 n q- model makes predictions less reliable, and in general, unambiguously discerning the isolated structures requires the combination of accurate computational and experimental data.

8.
Zhonghua Er Ke Za Zhi ; 52(4): 292-7, 2014 Apr.
Artigo em Chinês | MEDLINE | ID: mdl-24915918

RESUMO

OBJECTIVE: To analyze the relationship between the ictal onset zone and dominant interictal epileptiform foci in tuberous sclerosis complex (TSC) patients. METHOD: Clinical data of 20 patients with TSC which had epileptic seizures during Video-EEG monitoring was assessed. Consistency and dominance of focal interictal epileptiform activity and the ictal onset zone were identified. Concordance between interictal and ictal findings was analyzed. RESULT: Of the 20 patients, 7 were female, and 13 were male. The age of epilepsy onset was from 15 d to 6 years. The Video-EEG monitoring age was from 6 months to 11 years. Family history was found in three cases. Abnormality in neuroimaging existed in 17 of 18 patients who were examined. Interictal EEG showed hypsarrhythmia in 3 patients, multifocal epileptiform activity with a dominant focus in 12 patients, both focal and generalized discharges in 2 patients, and only focal discharges in 3 patients. The seizures types during EEG monitoring included epileptic spasms, partial seizure, atypical absence, and generalized or focal myoclonic seizure. The most common seizure type was partial seizure and then epileptic spasms. EEG in 4 patients with epileptic spasms showed ictal generalized discharges and interictal hypsarrhythmia or generalized discharges. Clinical manifestation of epileptic spasms was asymmetric in 3 patients. Lateralization and location of interictal and ictal discharges were consistent in 2 of the 3 patients, while only lateralization consistency in 1 of the 3 patients. Partial seizures as the only seizure type were monitored in 13 patients. Of the 13 patients, lateralization and location of interictal and ictal discharges were inconsistent in 2 patients (15%), consistent in 8 patients (62%), lateralization or location consistent in 2 patients (15%). One case could not be analyzed because of uncertainty of lateralization and location of seizure onset. CONCLUSION: In the majority of patients with TSC, multifocal interictal epileptiform activity is present, in which a most dominance of focal epileptiform activity could be found. For some epileptic seizures or the majority of partial seizures, the ictal onset zone is concordant with the dominance of focal interictal epileptiform foci. The concordance might have positioning reference significance for preoperative evaluation of epilepsy surgery.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/fisiopatologia , Eletroencefalografia/estatística & dados numéricos , Convulsões/diagnóstico , Esclerose Tuberosa/diagnóstico , Encéfalo/patologia , Córtex Cerebral/patologia , Córtex Cerebral/fisiopatologia , Criança , Pré-Escolar , Epilepsias Parciais/diagnóstico , Epilepsias Parciais/etiologia , Epilepsias Parciais/fisiopatologia , Feminino , Humanos , Lactente , Recém-Nascido , Imagem por Ressonância Magnética , Masculino , Valor Preditivo dos Testes , Estudos Retrospectivos , Convulsões/etiologia , Convulsões/fisiopatologia , Esclerose Tuberosa/complicações , Esclerose Tuberosa/fisiopatologia
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