AVS 57th International Symposium & Exhibition
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuA

Paper NS-TuA4
Spectroscopic Identification of Bond Strain and P Interactions in a Series of Saturated Carbon-Cage Molecules: Adamantane, Twistane, Octahedrane, and Cubane

Tuesday, October 19, 2010, 3:00 pm, Room La Cienega

Session: Carbon-Based Nanomaterials
Presenter: T.M. Willey, Lawrence Livermore National Lab
Authors: T.M. Willey, Lawrence Livermore National Lab
J.R.I. Lee, Lawrence Livermore National Lab
D. Brehmer, SLAC National Accelerator Lab
L. Landt, Lawrence Livermore National Lab
P.R. Schreiner, Justus-Liebig Univ. Giessen, Germany
A.A. Fokin, Justus-Liebig Univ. Giessen, Germany
B.A. Tkachenko, Justus-Liebig Univ. Giessen, Germany
N.A. Fokina, Justus-Liebig Univ. Giessen, Germany
T. van Buuren, Lawrence Livermore National Lab
Correspondent: Click to Email
Novel nanocarbons such as fullerenes, nanotubes, graphene, and nanodiamond reside at the cutting edge of nanoscience and technology. Along with chemical functionalization, geometrical constraints (such as extreme curvature in nanotubes or graphene, or defects within or at the surfaces of nanodiamond crystallites) can modify the electronic states of the nanocarbon material. Understanding the effects of bond strain on electronic structure is critical to developing nanoelectronic applications based on these materials. This paper presents a fundamental study of how bond strain affects electronic structure in a benchmark series of novel saturated carbon cage compounds. Adamantane, C10H16, the smallest diamondoid, and arguably the smallest nanodiamond crystallite, has carbon atoms essentially commensurate with diamond lattice positions and possesses by far the least bond strain of the series. Twistane has the same stoichiometry (C10H16), but introduces some strain into the cage. Octahedrane (C12H12) and cubane (C8H8) contain increasing amounts of bond strain, culminating in cubane where carbon-carbon bonds lie either parallel, or orthogonal to one another. Using gas-phase near-edge x-ray absorption fine structure spectroscopy to probe the unoccupied electronic states, we observe two major progressions across this series. First, a broad C-C σ* resonance in the absorption splits into two more narrow and intense resonances with increasing strain. Second, the first manifold of states previously associated with tertiary C-H σ* in the diamondoid series appears to broaden and shift to lower energy. This feature is more than twice as intense in cubane as octadedrane, even though these two molecules have similar stoichiometries (CxHx). We attribute the additional intensity to π* states, indicating a high degree of π interaction between parallel C-C bonds in the cubane.