Bindungsmuster zweier C₉₀‐Isomere, bestimmt durch Strukturaufklärung von C₉₀Cl₃₂

Abstract

Seit der Entdeckung der Fullerene C 60 und C 70 sind die Isolierung und Charakterisierung der stabilen Isomere höherer Fullerene ein bedeutendes Forschungsgebiet. Wegen des sehr geringen Gehalts an höheren Fullerenen im fullerenhaltigen Ruß sind allerdings vielstufige HPLC-Verfahren für ihre Abtrennung nötig. Ihre (allerdings nicht immer eindeutige) Charakterisierung erfolgt üblicherweise 13 C-NMR-spektroskopisch, unterstützt durch Berechnungen ihrer relativen Stabilität.[1] Eine weitere Methode zur Charakterisierung höherer Fullerene macht von ihren Derivaten Gebrauch, die in der Regel viel leichter getrennt werden können. So sind in letzter Zeit die Strukturen einiger Isomere von C 74 ,[2] C 76 , [3] C 78 , [2,4] C 80 [5] und C 84 [6] in Form ihrer halogenierten, trifluormethylierten oder anderer Derivate untersucht worden.Für noch höhere Fullerene ergibt sich ein weiteres Problem aus der steigenden Zahl ihrer Käfigisomere, die der Regel der isolierten Pentagons (Isolated Pentagon Rule, IPR) folgen.[7] So traten im Fall von C 90 , das eine "magische" 6n-Zahl von C-Atomen sowie 46 mögliche IPR-Isomere aufweist, [7,8] Unsicherheiten bei der Zuordnung von 13 C-NMRSpektrallinien in Isomerengemischen auf.[

Isolation of a Small Carbon Nanotube: The Surprising Appearance of D5h(1)‐C90

“…[15,16] To further compare D 5h (1)-C 90 with C 70 , we examined the pyramidalization (POAV) angles for the carbon atoms in these fullerenes. [17] For C 60 , the POAV angle is 11.64 (10). [17] For D 5h (1)-C 90 , the POAV angles are: a, 11.91(8); b, 11.95(9); c, 11.70(15); d, 10.37 (19); e, 7.2(2); f, 5.51(15)8; the corresponding angles for C 70 are: a, 11.87(9); b, 12.01(9); c, 11.44 (16); d, 10.18 (17); e, 8.66(16)8.…”

“…The 13 C NMR spectroscopic studies of Achiba et al [3] produced no evidence for the presence of D 5h (1)-C 90 in their samples, and the products obtained upon functionalization did not reveal the presence of the D 5h isomer either. [9,10] It has been reported that the incorporation of metal salts in the graphite rods used in the electric-arc synthesis can change the composition of fullerenes formed. For example, the addition of gadolinium to the graphite electrodes led to the isolation of isomers D 3d -C 84 and D 6h -C 84 .…”

“…[9] The chlorination of a mixture of higher fullerenes through treatment with SbCl 5 yielded a crystalline material containing C 90 Cl 32 . [10] Crystallographic analysis revealed that a single crystal contained a mixture of two isomers that utilized the C 2v (46)-C 90 and C s (34)-C 90 cages.Carbon soot was obtained by vaporizing a graphite rod filled with Sm 2 O 3 and graphite powder in an electric arc as outlined previously. [11,12] The carbon soot was extracted with o-dichlorobenzene, and the soluble extract was subjected to a multistage high pressure liquid chromatographic (HPLC) isolation process involving three complementary chromatographic columns (Buckyprep-M, Buckyprep, and 5PBB) with either chlorobenzene or toluene as the eluent.…”

“…[9] The chlorination of a mixture of higher fullerenes through treatment with SbCl 5 yielded a crystalline material containing C 90 Cl 32 . [10] Crystallographic analysis revealed that a single crystal contained a mixture of two isomers that utilized the C 2v (46)-C 90 and C s (34)-C 90 cages.…”

The Most Stable IPR Isomer of C88 Fullerene, Cs‐C88 (17), Revealed by X‐ray Structures of C88Cl16 and C88Cl22

“…Generally, triple Cl···Cl contacts in fullerene chlorides destabilize the whole molecule; they are absent even in more overcrowded chlorinated molecules such as C 76 Cl 34 , [10] and C 90 Cl 32 . [11] Notably, so far triple Cl···Cl contacts were found in only one case, C 78 (1)Cl 30 . [12] The addition pattern in C s -C 88 (17)Cl 22 with a chain attachment on one pole and more distant attachment on the second pole closely resembles that seen in C 76 Cl 18 [9a] or C 76 Cl 24 .…”