Unstable Isomer of C90Fullerene Isolated as Chloro Derivatives, C90(1)Cl10/12

Vibrational anatomy of C90, C96, and C100 fullertubes: probing Frankenstein's skeletal structures of fullerene head endcaps and nanotube belt midsection

Fullertubes are tubular fullerenes with nanotube-like middle section and fullerene-like endcaps. To understand how this intermediate form between spherical fullerenes and nanotubes is reflected in the vibrational modes, we performed comprehensive studies of IR and Raman spectra of fullertubes C₉₀-D_5h, C₉₆-D_3d, and C₁₀₀-D_5d. An excellent agreement between experimental and DFT-computed spectra enabled a detailed vibrational assignment and allowed an analysis of the localization degree of the vibrational modes in different parts of fullertubes. Projection analysis was performed to establish an exact numerical correspondence between vibrations of the belt midsection and fullerene headcaps to the modes of nanotubes and fullerene C₆₀-I_h. As a result, we could not only identify fullerene-like and CNT-like vibrations of fullertubes, but also trace their origin in specific vibrational modes of CNT and C₆₀-I_h. IR spectra were found to be dominated by vibrations of fullerene-like caps resembling IR-active modes of C₆₀-I_h, whereas in Raman spectra both caps and belt vibrations are found to be equally active. Unlike the resonance Raman spectra of CNTs, in which only two single-phonon bands are detected, the Raman spectra of fullertubes exhibit several CNT-like vibrations and thus provide additional information on nanotube phonons.

Fullertubes: Cylindrical Carbon with Half-Fullerene End-Caps and Tubular Graphene Belts, Their Chemical Enrichment, Crystallography of Pristine C90-D5h(1) and C100-D5d(1) Fullertubes, and Isolation of C108, C120, C132, and C156 Cages of Unknown Structures

We report a chemical separation method to isolate fullertubes: a new and soluble allotrope of carbon whose structure merges nanotube, graphene, and fullerene subunits. Fullertubes possess single-walled carbon nanotube belts resembling a rolled graphene midsection, but with half-fullerene end-caps. Unlike nanotubes, fullertubes are reproducible in structure, possess a defined molecular weight, and are soluble in pristine form. The high reactivity of amines with spheroidal fullerene cages enables their removal and allows a facile isolation of C₉₆-D_3d(3), C₉₀-D_5h(1), and C₁₀₀-D_5d(1) fullertubes. A nonchromatographic step (Stage 1) uses a selective reaction of carbon cages with aminopropanol to permit a highly enriched sample of fullertubes. Spheroidal fullerenes are reacted and removed by attaching water-soluble groups onto their cage surfaces. With this enriched (100-1000 times) fullertube mixture, Stage 2 becomes a simple HPLC collection with a single column. This two-stage separation approach permits fullertubes in scalable quantities. Characterization of purified C₁₀₀-D_5d(1) fullertubes is done with samples isolated in pristine and unfunctionalized form. Surprisingly, C₆₀ and C₁₀₀-D_5d(1) are both purplish in solution. For X-ray crystallographic analysis, we used decapyrrylcorannulene (DPC). Isomerically purified C₉₀ and C₁₀₀ fullertubes were mixed with DPC to obtain black cocrystals of 2DPC{C₉₀-D_5h(1)}·4(toluene) and 2DPC{C₁₀₀-D_5d(1)}·4(toluene), respectively. A serendipitous outcome of this chemical separation approach is the enrichment and purification of several unreported larger carbon species, e.g., C₁₂₀, C₁₃₂, and C₁₅₆. Isolation of these higher cage species represents a significant advance in the unknown experimental arena of C₁₀₀-C₂₀₀ structures. Our findings represent seminal experimental evidence for the existence of two mathematically predicted families of fullertubes: one family with an axial hexagon with the other series based on an axial pentagon ring. Fullertubes have been predicted theoretically, and herein is their experimental evidence, isolation, and initial characterization.

Skeletal Transformation of a Classical Fullerene C88 into a Nonclassical Fullerene Chloride C84Cl30 Bearing Quaternary Sequentially Fused Pentagons

A classical fullerene is composed of hexagons and pentagons only, and its stability is generally determined by the Isolated-Pentagon-Rule (IPR). Herein, high-temperature chlorination of a mixture containing a classical IPR-obeying fullerene C₈₈ resulted in isolation and X-ray crystallographic characterization of non-IPR, nonclassical (NC) fullerene chloride C₈₄(NC2)Cl₃₀ (1) containing two heptagons. The carbon cage in C₈₄(NC2)Cl₃₀ contains 14 pentagons, 12 of which form two pairs of fused pentagons and two groups of quaternary sequentially fused pentagons, which have never been observed in reported carbon cages. All 30 Cl atoms form an unprecedented single chain of ortho attachments on the C₈₄ cage. A reconstruction of the pathway of the chlorination-promoted skeletal transformation revealed that the previously unknown IPR isomer C₈₈(3) is converted into 1 by two losses of C₂ fragments followed by two Stone-Wales rearrangements, resulting in the formation of very stable chloride with rather short C-Cl bonds.