Endohedral nitride cluster fullerenes

Dunsch, Lothar; Krause, Matthias; Noack, Joachim; Georgi, P.

doi:10.1016/j.jpcs.2003.03.002

Cited by 171 publications

(355 citation statements)

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“…EMFs were obtained by arc-discharge synthesis under He atmosphere with as mall amount of CH 4 gas using graphite rods packed with am ixture of Ti,lanthanide (Y,Ce, Nd, Gd, Dy,Er, or Lu), and agraphite powder.T he role of CH 4 in this type of synthesis is similar to that of NH 3 [2] in the synthesis of nitride clusterfullerenes:the reactive gas increases selectivity of the process by suppressing the formation of empty fullerenes and making the EMFs with desired central atom(s) the main products.F igure 1s hows that under optimized conditions,carbide clusterfullerenes are the most abundant EMF products for Lu, Dy,Er, Y, and Gd. However, the yield of these EMFs decreases with the ionic radius faster than the yield of M 2 TiC@C 80 -I, and Dy 2 TiC@C 80 -I can be produced with ahigh degree of selectivity and relatively high absolute yield.…”

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“…[1] Theu se of NH 3 as areactive gas instead of molecular nitrogen resulted in much higher selectivity in the synthesis of nitride clusterfullerenes as the yield of empty fullerenes in such conditions decreased dramatically. [2] Discovery of nitride clusterfullerenes triggered exhaustive studies of other clusterfullerenes, resulting in av ariety of EMF families with endohedral S, [3] O,…”

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Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy₂TiC@C₈₀ and Its Congener Dy₂TiC₂@C₈₀

et al. 2015

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The use of methane as ar eactive gas dramatically increases the selectivity of the arc-discharge synthesis of M-Ticarbide clusterfullerenes (M = Y, Nd, Gd, Dy,E r, Lu). Optimization of the process parameters allows the synthesis of Dy 2 TiC@C 80 -I and its facile isolation in asingle chromatographic step.An ew type of cluster with an endohedral acetylide unit, M 2 TiC 2 @C 80 ,i sd iscovered along with the second isomer of M 2 TiC@C 80 .D y 2 TiC@C 80 -(I,II) and Dy 2 TiC 2 @C 80 -I are shown to be single-molecule magnets (SMM), but the presence of the second carbon atom in the cluster Dy 2 TiC 2 @C 80 leads to substantially poorer SMM properties.The field of endohedral metallofullerene (EMF) research was revolutionized in 1999, when it was discovered that the presence of small amounts of nitrogen gas in the arc-discharge generator afforded Sc 3 N@C 80 ,anew type of EMF with at rimetalnitride cluster inside the carbon cage.[1] Theu se of NH 3 as areactive gas instead of molecular nitrogen resulted in much higher selectivity in the synthesis of nitride clusterfullerenes as the yield of empty fullerenes in such conditions decreased dramatically.[2] Discovery of nitride clusterfullerenes triggered exhaustive studies of other clusterfullerenes, resulting in av ariety of EMF families with endohedral S, [3] O,[4] C 2 , [5] CH, [6] CN, [7] and other nonmetal units.[8]One of the advantages of the trimetallic cluster in nitride clusterfullerenes is the possibility of combining two or even three different metals within one EMF molecule.M ixedmetal nitride clusterfullerenes may exhibit new properties not present in homometallic nitride clusterfullerenes.E xamples include unusual redox behavior, [9] stabilization of unconventional carbon cages, [10] and strong variation of chemical reactivity [11] and magnetization behavior [12] depending on the number of lanthanide ions in the cluster.H owever, ad isadvantage of the mixed-metal EMFs is the increased complexity of their chromatographic separation.Whereas nitride clusterfullerenes are usually formed with Group III metals,s uch as Sc, Y, and trivalent lanthanides, [13] Yang et al. demonstrated that as ingle Ti ion can be introduced into the mixed-metal nitride cluster together with Sc or Y. [14] Due to the trivalent Ti,M 2 TiN@C 80 clusterfullerenes have unusual electronic and chemical properties. [15] Recently,i na na ttempt to obtain Ti-based nitride clusterfullerenes with Lu using NH 3 as ar eactive gas or melamine as as olid organic nitrogen source,w eh ave discovered an ew type of clusterfullerene,L u 2 TiC@C 80 , which has an endohedral m 3 -carbide ion and aT i ÀCd ouble bond.[16] Them olecule is an isostructural analogue of Lu 2 ScN@C 80 ,i nw hich the Sc-N fragment is replaced by the isoelectronic Ti = Cfragment. Unfortunately,inthe Lu/Ti/NH 3 and Lu/Ti/melamine syntheses,L u 2 TiC@C 80 is only am inor by-product;t he products are predominantly Lu 3 N@C 2n nitride clusterfullerenes,which precludes further exploration of this new type of clusterfullerenes.H ...

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Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy₂TiC@C₈₀ and Its Congener Dy₂TiC₂@C₈₀

et al. 2015

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“…I ncorporation of magnetic ions in molecular clusters can lead to the formation of so-called single-molecule magnets (SMMs). 1 These molecules are characterized by slow magnetic relaxation, making them candidates for applications in quantum computing, spintronics, and high-density storage devices. Dy, 3a,b or Ho 3c ) were the first mononuclear complexes shown to exhibit SMM behavior.…”

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An Endohedral Single-Molecule Magnet with Long Relaxation Times: DySc₂N@C₈₀

et al. 2012

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The magnetism of DySc 2 N@C 80 endofullerene was studied with X-ray magnetic circular dichroism (XMCD) and a magnetometer with a superconducting quantum interference device (SQUID) down to temperatures of 2 K and in fields up to 7 T. XMCD shows hysteresis of the 4f spin and orbital moment in Dy III ions. SQUID magnetometry indicates hysteresis below 6 K, while thermal and nonthermal relaxation is observed. Dilution of DySc 2 N@C 80 samples with C 60 increases the zero-field 4f electron relaxation time at 2 K to several hours. I ncorporation of magnetic ions in molecular clusters can lead to the formation of so-called single-molecule magnets (SMMs).1 These molecules are characterized by slow magnetic relaxation, making them candidates for applications in quantum computing, spintronics, and high-density storage devices. Investigations on the magnetism of single ions inside fullerenes started with Gd@C 82 , which turned out to be paramagnetic down to 3 K. 9a For Dy@C 82 , superconducting quantum interference device (SQUID) and X-ray magnetic circular dichroism (XMCD) measurements revealed paramagnetic behavior down to 1.8 K.9b−e The observed magnetic moment is reduced in this system compared to the free trivalent Dy ion, which is attributed to a quenched orbital moment due to the crystal field splitting from the carbon cage and/or electron back-donation from the cage to the Dy ion. In contrast, C 80 NCFs have a carbon cage with a closed shell, and less coupling between the moments of the metal ions and a diamagnetic cage is expected. SQUID magnetization measurements on Ln 3 N@C 80 (Ln = Tb and Ho) 10a,b are in line with a model where the LF of the N 3− ion induces an easy axis for the individual Ln III moments directed along the respective Ln−N bond. In this model the magnetic anisotropy due to the LF is strong enough that the Ln III moments do not align with the external field but instead parallel to the bond directions. ) and Er x Sc 3−x N@ C 80 10d (x = 1, 2) above 1.8 K showed paramagnetism without hysteresis.In the present case we have a single Dy III ion in a diamagnetic carbon cage (see Figure 1). Since Sc III ions are not paramagnetic, the LF due to the N 3− ion will result in magnetic anisotropy directed along the Dy−N bond. Furthermore, if the LF stabilizes a ground state with a large J z , the prerequisite for magnetic bistability is fulfilled.

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“…[1][2][3][4][5] They exhibit a variety of new structural, magnetic, and electronic properties that are important for potential applications in electronics and medicine. [1][2][3][4][5][6][7] Numerous endohedral fullerenes with various encaged species and various forms of the carbon cage have been isolated recently. The latter exhibits a large variety of cavity sizes ranging from C 60 to C 100 .…”

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“…The latter exhibits a large variety of cavity sizes ranging from C 60 to C 100 . [1][2][3][4][5][6][7][8][9][10][11][12] There have even been cages reported that do not obey the isolated pentagon rule (IPR). These non-IPR cages include Sc 2 @C 66 , [8] Sc 3 N@C 68 , [9, 11c] Sc 2 C 2 @C 68 , [13] and La 2 @C 72 .…”

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Violating the Isolated Pentagon Rule (IPR): The Endohedral Non‐IPR C₇₀ Cage of Sc₃N@C₇₀

2007

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Endohedral nitride cluster fullerenes

Cited by 171 publications

References 10 publications

Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy₂TiC@C₈₀ and Its Congener Dy₂TiC₂@C₈₀

Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy₂TiC@C₈₀ and Its Congener Dy₂TiC₂@C₈₀

An Endohedral Single-Molecule Magnet with Long Relaxation Times: DySc₂N@C₈₀

Violating the Isolated Pentagon Rule (IPR): The Endohedral Non‐IPR C₇₀ Cage of Sc₃N@C₇₀

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Endohedral nitride cluster fullerenes

Cited by 171 publications

References 10 publications

Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy2TiC@C80 and Its Congener Dy2TiC2@C80

Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy2TiC@C80 and Its Congener Dy2TiC2@C80

An Endohedral Single-Molecule Magnet with Long Relaxation Times: DySc2N@C80

Violating the Isolated Pentagon Rule (IPR): The Endohedral Non‐IPR C70 Cage of Sc3N@C70

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Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy₂TiC@C₈₀ and Its Congener Dy₂TiC₂@C₈₀

Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy₂TiC@C₈₀ and Its Congener Dy₂TiC₂@C₈₀

An Endohedral Single-Molecule Magnet with Long Relaxation Times: DySc₂N@C₈₀

Violating the Isolated Pentagon Rule (IPR): The Endohedral Non‐IPR C₇₀ Cage of Sc₃N@C₇₀