Gigantic C₁₂₀ Fullertubes: Prediction and Experimental Evidence for Isomerically Purified Metallic [5,5] C₁₂₀-D_5d(1)...

We report the first experimental characterization of isomerically pure and pristine C₁₂₀ fullertubes, [5,5] C₁₂₀-D_5d(1) and [10,0] C₁₂₀-D_5h(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-D_5d(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-D_5d(10766) fullertube has an end-cap derived from C₈₀-I_h 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-D_5d(1) fullertube. C₁₂₀ isomer II matches a [10,0] C₁₂₀-D_5h(10766) fullertube. These structural assignments are further supported by Raman data showing metallic character for [5,5] C₁₂₀-D_5d(1) and nonmetallic character for C₁₂₀-D_5h(10766). STM imaging reveals a tubular structure with an aspect ratio consistent with a [5,5] C₁₂₀-D_5d(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.