RESUMEN
While the strong interaction between the internal unit and the fullerene cage inside metallofullerenes is widely acknowledged, how the cage transformation interacts with the cluster configuration remains elusive. For this purpose, we herein synthesized three metallofullerene molecules with an easy-to-compare cluster configuration and cage arrangement, namely Lu3N@Cs(17 490)-C76, Lu3N@C2(22 010)-C78, and Lu3N@D3h(5)-C78. The three lutetium-based nitride clusterfullerenes (NCFs) with small C76-78 carbon cages were synthesized by a modified arc-discharge method and their structures were unambiguously confirmed by X-ray crystallography. Notably, the cage transformation from Cs(17 490)-C76 to C2(22 010)-C78via a simple C2-unit insertion leads to a remarkable configuration change of the encapsulated Lu3N cluster from an unusual asymmetric plane to a common symmetric one. This close correlation between the cluster configuration and cage transformation is further confirmed by the pyramidal Lu3N cluster in Lu3N@D3h(5)-C78 other than the symmetric planar Lu3N unit in Lu3N@C2(22 010)-C78, as a result of an even larger difference in the cage arrangement. Astonishingly, such a cluster shrinkage, accompanied by an increase in the cage size from Cs(17 490)-C76 to D3h(5)-C78, is dramatically opposite to the cluster expansion with cage elongation found in La2C2- or Y2C2-based metallofullerenes.
RESUMEN
Four silver thiolate clusters, [H3 O][(Ag3 S3 )(BF4 )@Ag27 (tBuS)18 (hfac)6 H2 O]â H2 O (1; hfac = hexafluoroacetylacetone), [(Ag3 S3 )(CF3 CO2 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]â CF3 CO2 â 4 CH3 CN (2), [(Ag3 S3 )(MoO4 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]â 2 CH3 CN (3), and [(Ag3 S3 )(CrO4 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]â 4 CH3 CN (4), were isolated. They have similar nestlike structures assembled by an [Ag3 S3 ]3- template together with one of the BF4 - , CF3 CO2 - , MoO4 2- , or CrO4 2- anions. Interestingly, the solid-state emissions of 2-4 are dependent on the templating anions and are tunable from green to orange and then to red by changing the template from CF3 CO2 - to MoO4 2- and to CrO4 2- , and this may be correlated to the charge transfer between these templates to metal atoms. This work helps to understand the templating role of heteroanions and the relationship between structure and properties.
RESUMEN
The single-crystal micro/nanostructures of fullerene species, namely C60 and C70 , have been previously studied, but studies on the morphology and properties of higher fullerenes have rarely been reported due to the limited amount of samples and their ellipsoidal isomeric structures. Herein, we report the formation of three-dimensional (3D) micro-cubes and micro-dice of a higher fullerene (C78 ) via a facile liquid-liquid interfacial precipitation (LLIP) method. The micro-cubes were prepared by regulating the concentration of C78 in trimethylbenzene (TMB) and the volume ratio of TMB and isopropanol. Interestingly, the micro-cubes are transformed into micro-dice with an open-hole on each crystal face by simply shaking the solution. X-ray diffraction and Fourier-transform infrared spectroscopic studies revealed a simple cubic unit cell with a lattice constant of 10.6â Å and intercalated TMB molecules in both crystals. The C78 cubic and dice-like microstructures exhibited enhanced photoelectrochemical and photoluminescence properties compared with pristine C78 powder, indicating their potential applications as photodetectors and photoelectric devices.
RESUMEN
A novel radical reaction of monometallofullerene Y@C2v(9)-C82 with N-arylbezamidine (1) is successfully conducted through catalysis with silver carbonate. The high-performance liquid chromatographic and mass spectrum results demonstrate that the reaction is highly regioselective to afford only one monoadduct (2) with an imidazoline group added on C82 cage, and computations through density functional theory reveal the addition group is attached to a specific [5, 6]-bond (C20-C76) near the Y atom. Furthermore, the analysis of prymidalization angle of the carbon atoms demonstrates the geometry of carbon cage is in favor of the regioselective formation of isomer (20, 76).
RESUMEN
Fullerene cages are ideal hosts to encapsulate otherwise unstable metallic clusters to form endohedral metallofullerenes (EMFs). Herein, a novel Ti2C2 cluster with two titanium atoms bridged by a C2-unit has been stabilized by three different fullerene cages to form Ti2C2@D3h(5)-C78, Ti2C2@C3v(8)-C82, and Ti2C2@Cs(6)-C82, representing the first examples of unsupported titanium carbide clusters. Crystallographic results show that the configuration of the Ti2C2 cluster changes upon cage variation. In detail, the Ti2C2 cluster adopts a butterfly shape in Ti2C2@C3v(8)-C82 and Ti2C2@Cs(6)-C82 with Ti-C2-Ti dihedral angles of 156.35 and 147.52° and Ti-Ti distances of 3.633 and 3.860 Å, respectively. In sharp contrast, a stretched planar geometry of Ti2C2 is observed in Ti2C2@D3h(5)-C78, where a Ti-C2-Ti angle of 176.87° and a long Ti-Ti distance of 5.000 Å are presented. Consistently, theoretical calculations reveal that the cluster configuration is very sensitive to the cage shape which eventually determines the electronic structures of the hybrid EMF-molecules, thus adding new insights into modern coordination chemistry.
RESUMEN
Encapsulating one to three metal atoms or a metallic cluster inside fullerene cages affords endohedral metallofullerenes (EMFs) classified as mono-, di-, tri-, and cluster-EMFs, respectively. Although the coexistence of various EMF species in soot is common for rare-earth metals, we herein report that europium tends to prefer the formation of mono-EMFs. Mass spectroscopy reveals that mono-EMFs (Eu@C2n ) prevail in the Eu-containing soot. Theoretical calculations demonstrate that the encapsulation energy of the endohedral metal accounts for the selective formation of mono-EMFs and rationalize similar observations for EMFs containing other metals like Ca, Sr, Ba, or Yb. Consistently, all isolated Eu-EMFs are mono-EMFs, including Eu@D3h (1)-C74 , Eu@C2v (19138)-C76 , Eu@C2v (3)-C78 , Eu@C2v (3)-C80 , and Eu@D3d (19)-C84 , which are identified by crystallography. Remarkably, Eu@C2v (19138)-C76 represents the first Eu-containing EMF with a cage that violates the isolated-pentagon-rule, and Eu@C2v (3)-C78 is the first C78 -based EMF stabilized by merely one metal atom.
RESUMEN
A series of Er-based nitride clusterfullerenes (NCFs), Er3N@C80-88, have been successfully synthesized and isolated. In particular, Er3N@Ih(7)-C80, Er3N@D5h(6)-C80, Er3N@C2v(9)-C82, Er3N@Cs(51365)-C84, and Er3N@D2(35)-C88 have been characterized by single-crystal X-ray diffraction (XRD) for the first time. The planar configuration of the inserted Er3N cluster is identified unambiguously and the Er-N distances increase in accordance with cage expansion to maintain strong metal-cage interactions. Additionally, the electrochemical properties of the Er3N@C80-88 series are studied by means of cyclic voltammetry. It is found that the first reduction potentials are roughly similar for all compounds under study, while the first oxidation potentials are cathodically shifted along with the increase of the cage size in the Er3N@C2n (2n = 80, 84, 86, 88) series, leading to a decrease in the corresponding electrochemical band gaps. Nevertheless, for Er3N@C2v(9)-C82, a good electron donating ability is manifested by its relatively small first oxidation potential, which results from the relatively higher energy level of the highest occupied molecular orbital. The redox behaviors observed in such Er3N-based NCFs may promise their great potential applications in donor-acceptor systems.
RESUMEN
Interactions between the inner and outer units through a fullerene cage are of fundamental importance for the creation of molecular spintronics and machines, but the mechanism of such through-cage interplay is still unclear. In this work, we have designed and synthesized two prototypical compounds which contain only a single europium atom inside the cage and merely a tungsten atom coordinating outside to clarify the interactions between the endohedral and exohedral metallic units. They are obtained by reacting a tungsten complex W(CO)4(Ph2PC2H4PPh2) (1) with the corresponding metallofullerenes in a highly regioselective manner (2a for Eu@C 2(5)-C82 and 2b for Eu@C 2(13)-C84). On the one hand, the endohedral Eu-doping has changed the LUMO distribution on C 2(5)-C82/C 2(13)-C84 dramatically, via electron transfer, which governs the addition pattern of the exohedral tungsten resulting in surprisingly high regioselectivity. On the other hand, the exohedral tungsten coordination with Eu@C 2(5)-C82/Eu@C 2(13)-C84 has restricted the motion of the internal europium ion to some extent by changing the electrostatic potentials, as confirmed by the X-ray results of 2a, 2b and the corresponding pristine metallofullerenes cocrystallized with Ni(OEP) (OEP is the dianion of octaethylporphyrin). We now make it clear that the interplay between the endohedral and exohedral metallic units can be realized in a single system by means of intramolecular charge transfer, which may arouse interest in the design and utilization of novel metallofullerene-based molecular devices.
RESUMEN
Charge transfer in metallofullerene/porphyrin cocrystals is revealed for the first time. Originated from the different solvents for crystallization, distinct stacking manners are presented in the two types of cocrystals. It is demonstrated that intermolecular packing, next to the nature of the corresponding electron donors and acceptors, dominates the charge transfer processes.
RESUMEN
Revealing the transformation routes among existing fullerene isomers is key to understanding the formation mechanism of fullerenes which is still unclear now because of the absence of typical key links. Herein, we have crystallographically identified four new fullerene cages, namely, C 2(27)-C88, C 1(7)-C86, C 2(13)-C84 and C 2(11)-C84, in the form of Eu@C2n , which are important links to complete a transformation map that contains as many as 98% (176 compounds in total) of the reported metallofullerenes with clear cage structures (C2n , 2n = 86-74). Importantly, the mutual transformations between the metallofullerene isomers included in the map require only one or two well-established steps (Stone-Wales transformation and/or C2 insertion/extrusion). Moreover, structural analysis demonstrates that the unique C 2(27)-C88 cage may serve as a key point in the map and is directly transformable from a graphene fragment. Thus, our work provides important insights into the formation mechanism of fullerenes.
RESUMEN
The sub-nanometer cavity of fullerene cages is an ideal platform to accommodate otherwise unstable species for accurate structural characterization with, for example, rather accurate single crystal X-ray diffraction (XRD) crystallography. Herein, we report the successful entrapment of an isolated Ti3C3 moiety inside the icosahedral-C80 cage to form Ti3C3@Ih-C80 via an arc-evaporation process in the gas phase. The single crystal XRD crystallographic results unambiguously reveal that the C3-unit adopts an unprecedented cyclopropane-like structure which coordinates with the three titanium atoms in an unexpected fashion where the triangular C3-unit is nearly perpendicular to the Ti3-plane. The intercalation of a cyclopropanated C3-unit into the titanium layer is thus unambiguously confirmed. The theoretical results reveal that the Ti3C3 cluster transfers six electrons to the Ih-C80 cage so that each titanium atom has a positive charge slightly above +2 and the C3-unit is negatively charged with about -1. It is noteworthy that this is the first observation of the cyclopropane-coordination fashion in any reported organometallic complex, providing new insights into coordination chemistry.