We report a chemical separation method to isolate f ullertubes: 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 C 96 -D 3d (3), C 90 -D 5h (1), and C 100 -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 C 100 -D 5d (1) fullertubes is done with samples isolated in pristine and unfunctionalized form. Surprisingly, C 60 and C 100 -D 5d (1) are both purplish in solution. For X-ray crystallographic analysis, we used decapyrrylcorannulene (DPC). Isomerically purified C 90 and C 100 fullertubes were mixed with DPC to obtain black cocrystals of 2DPC{C 90 -D 5h (1)}•4(toluene) and 2DPC{C 100 -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., C 120 , C 132 , and C 156 . Isolation of these higher cage species represents a significant advance in the unknown experimental arena of C 100 -C 200 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.

Although fullerenes were discovered nearly 35 years ago, scientists still struggle to isolate "single molecule" tubular fullerenes larger than C 90 . In similar fashion, there is a paucity of reports for pristine single-walled carbon nanotubes (SWNTs). In spite of Herculean efforts, the isolation and properties of pristine members of these carbonaceous classes remain largely unfulfilled. For example, the low abundance of spherical and tubular higher fullerenes in electric-arc extracts (<0.01−0.5%) and multiplicity of structural isomers remain a major challenge. Recently, a new isolation protocol for highly tubular f ullerenes, also called f ullertubes, was reported. Herein, we describe spectroscopic characterization including 13 C NMR, XPS, and Raman results for purified [5,5] fullertube family members, D 5h -C 90 and D 5d -C 100 . In addition, DFT computational HOMO−LUMO gaps, polarizability indices, and electron density maps were also obtained. The Raman and 13 C NMR results are consistent with semiconducting and metallic properties for D 5h -C 90 and D 5d -C 100 , respectively. Our report suggests that short [5,5] fullertubes with aspect ratios of only ∼1.5−2 are metallic and could exhibit unique electronic properties.

We report the first experimental characterization of isomerically pure and pristine C120 fullertubes, [5,5] C120-D5d(1) and [10,0] C120-D5h(10766). These new molecules represent the highest aspect ratio fullertubes isolated to date; for example, the prior largest empty cage fullertube was [5,5] C100-D5d(1). This increase of 20 carbon atoms represents a gigantic leap in comparison to three decades of C60–C90 fullerene research. Moreover, the [10,0] C120-D5d(10766) fullertube has an end-cap derived from C80-Ih and is a new fullertube whose C40 end-cap has not yet been isolated experimentally. Theoretical and experimental analyses of anisotropic polarizability and UV–vis assign C120 isomer I as a [5,5] C120-D5d(1) fullertube. C120 isomer II matches a [10,0] C120-D5h(10766) fullertube. These structural assignments are further supported by Raman data showing metallic character for [5,5] C120-D5d(1) and nonmetallic character for C120-D5h(10766). STM imaging reveals a tubular structure with an aspect ratio consistent with a [5,5] C120-D5d(1) fullertube. With microgram quantities not amenable to crystallography, we demonstrate that DFT anisotropic polarizability, augmented by long-accepted experimental analyses (HPLC retention time, UV–vis, Raman, and STM) can be synergistically used (with DFT) to down select, predict, and assign C120 fullertube candidate structures. From 10 774 mathematically possible IPR C120 structures, this anisotropic polarizability paradigm is quite favorable to distinguish tubular structures from carbon soot. Identification of isomers I and II was surprisingly facile, i.e., two purified isomers for two possible structures of widely distinguishing features. These metallic and nonmetallic C120 fullertube isomers open the door to both fundamental research and application development.

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...

The goal of this research is to explore the world of larger size carbon cage clusters in the range of C100-C200. Despite the isolation of C60 nearly 30 years ago, many of these higher fullerenes remain a mystery. The paucity of scientific literature for these species is attributed to the following: their low yield in typical soot extracts, proliferation of structural isomers that create a separation nightmare, HPLC co-elution of contaminant fullerene and metallofullerene species, and lack of an efficient separation method. In this presentation, we discuss our recent advances in separation science that allows us to now isolate an emerging number of carbon cages in the range of C100-C200. Whether these structures are tubular (FullerTubes) or spheroidal remains to be seen.