Semiconducting and Metallic [5,5] Fullertube Nanowires: Characterization of Pristine D_5h(1)-C₉₀ and D_5d(1)-C₁₀₀

Abstract

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.

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

“…A 1g (10) at 1195 cm −1 is another medium-intensity Raman feature of C 100 largely originating from ungerade CNT vibration, this time B 2u (2) predicted at 1319 cm −1 . This CNT mode, mixed with B 1g (1) ( predicted at 1377 cm −1 ), also contributes to the second strongest non-resonant Raman feature of C 100 , A 1g (12) at 1301 cm −1 . In fact, the latter can be described as the Kekule vibration of the belt hexagons.…”

“…Fortuitously, the studies of tubular fullerenes, aka fullertubes, gained the new boost with the discovery of the isolation route based on their reduced chemical reactivity. 10,12 While fullerenes usually readily react with amino-alcohols, tubular fullerenes appeared to be significantly less reactive, which allowed their facile separation from other fullerenes. The main fullertubes obtained this way are C 90 -D 5h , C 96 -D 3d , and C 100 -D 5d (Fig.…”

A Metallofullertube of Ce2@C100 with a Carbon Nanotube Segment: Synthesis, Single‐Molecule Conductance and Supramolecular Assembly

“…Recently, Stevenson and Xie et al. successfully isolated several typical isomers of pristine fullertubes like D 5h (1)‐C 90 , D 3d (3)‐C 96 and D 5d (1)‐C 100 by selective chemical enrichment [6a,b] . Notably, the changes from semiconductors to metallic state have also been demonstrated, and such results indicate the unique electronic properties of fullertubes [6b] .…”

“…successfully isolated several typical isomers of pristine fullertubes like D 5h (1)‐C 90 , D 3d (3)‐C 96 and D 5d (1)‐C 100 by selective chemical enrichment [6a,b] . Notably, the changes from semiconductors to metallic state have also been demonstrated, and such results indicate the unique electronic properties of fullertubes [6b] . Chlorination is an effective strategy for capturing different isomers of fullertubes, but skeleton transformation usually occurs [7] .…”

Gigantic C120 Fullertubes: Prediction and Experimental Evidence for Isomerically Purified Metallic [5,5] C120-D5d(1) and Nonmetallic [10,0] C120-D5h(10766)

“…Of broad interest is whether fullertubes behave as fullerenes (C 60 , C 70 ), as single wall nanotubes (SWNTs), or neither. In 2021, a study showed a transition to metallic properties by inserting 10 carbon atoms from the shorter [5,5] C 90 -D 5h (1) fullertube to the longer [5,5] C 100 -D 5d (1) fullertube. In 2022, an excited state study of [5,5] C 90 -D 5h (1) fullertubes showed photophysical properties consistent with classical fullerenes.…”