Towards Perfunctionalized Dodecahedranes—En Route to C₂₀ Fullerene

Abstract

"One-pot" substitution of the twenty hydrogen atoms in pentagonal dodecahedrane (C(20)H(20)) by OH, F, Cl, and Br atoms is explored. Electrophilic insertion of oxygen atoms with DMDO and TFMDO as oxidizing reagents ended, far off the desired C(20)(OH)(20), in complex polyol mixtures (up to C(20)H(10)(OH)(10) decols, a trace of C(20)H(OH)(19)?). Perfluorination was successful in a NaF matrix but (nearly pure) C(20)F(20) could be secured only in very low yield. "Brute-force" photochlorination (heat, light, pressure, time) provided a mixture of hydrogen-free, barely soluble C(20)Cl(16) dienes in high yield and C(20)Cl(20) as a trace component. Upon electron-impact ionization of the C(20)Cl(16) material sequential loss of the chlorine atoms was the major fragmentation pathway furnishing, however, only minor amounts of chlorine-free C(20) (+) ions. "Brute-force" photobrominations delivered an extremely complex mixture of polybromides with C(20)HBr(13) trienes as the highest masses. The MS spectra exhibited exclusive loss of the Br substituents ending in rather intense singly, doubly, and triply charged C(20)H(4-0) (+(2+)(3+)) ions. The insoluble approximately C(20)HBr(13) fraction (C(20)Br(14) trienes as highest masses) obtained along a modified bromination protocol, ultimately allowed the neat mass selection of C(20) (-) ions. The C(20)Cl(16) dienes and C(20)H(0-3)Br(14-12) tri-/tetraenes, in spite of their very high olefinic pyramidalization, proved resistant to oxygen and dimerization (polymerization) but added CH(2)N(2) smoothly. Dehalogenation of the respective cycloaddition products through electron-impact ionization resulted in C(22-24)H(4-8) (+(2+)) ions possibly constituting bis-/tris-/tetrakis-methano-C(20) fullerenes or partly hydrogenated C(22), C(23), and C(24) cages.

C20 Carbon Clusters: Fullerene–Boat–Sheet Generation, Mass Selection, Photoelectron Characterization

“…[33] Replacement of the strongly bound hydrogen atoms by weakly bound chlorine or even more weakly bound bromine atoms, dehalogenation by electron-impact ionization of the highly to extremely strained "halogen-balls" C 20 Cl 20 or C 20 Br 20 , mass-selection of the C 20 À ion and PE spectroscopic characterization of 1 had surfaced as "state-of-the-art" strategies. [10,11,13] The synthetic part presented in the preceding papers [23,34] was successful to the extent that through "forcing" to "brute-force" halogenations of 1 the hydrogen-free C 20 Cl 16 dienes 11 and the hydrogen-poor C 20 H 0-3 Br 14-12 tri-/ tetraenes 12 became reproducibly accessible. Both materials survived sublimation at 200-250 8C/10 À4 Torr unchanged and, unlike the parents 7-9 were oxygen-insensitive, and could be handled without precautions.…”

Polyhedral Phenylacetylenes: The Interplay of Aromaticity and Antiaromaticity in Convex Graphyne Substructures

“…Further work produced other less positively curved and less symmetrical allotropes such as C 70 , as well as linearly-extended nanotubes. Additionally, theoretical papers have subsequently described smaller, higher-energy fullerene-like molecules such as C 20 , C 36 , and C 48 [3][4][5][6] (the most symmetrical isomer of which is analogous to Archimedean solid A3, the great rhombicuboctahedron, with 48 vertices and Oh symmetry), though no reasonable strategy for their synthesis has been forthcoming [7][8][9][10][11].…”

Five Regioisomers of Dimethyl Dodecahedrane Derivatives: A Hybrid DFT B3LYP Study

“…It is interesting to compare the results above with the case of C 20 H 18 X 2 (X = F, Cl, Br, OH). In this case, except for the dihydroxy derivative, 1,2-disubstituted derivatives have the highest energy whereas 1,16-derivatives have the lowest energy; however, in the dihydroxy derivatives, the increasing order is reversed [20,37].…”