Gold Fullerenes Au 32 : A 24-Carat Golden Fullerene** Mikael P. Johansson,* Dage Sundholm, and Juha Vaara For more than a decade, gold nanostructures have attracted the attention of experimentalists and theoreticians alike. Recent years have witnessed increased interest in gold- containing structures, as several fields of application have found the metal to be not only aesthetical, but also of practical use. [1] In contrast to carbon where the familiar buckminster- fullerene [2] came first, later to be followed by carbon nano- tubes, gold research started in reverse; gold nanotubes are already a synthetic reality. [3] Au 32 has to date been considered a moderately uninteresting molecule, just one among the many gold clusters. The most stable structure has been suggested to be space-filling, [4,5] like the majority of all metal clusters studied to date. Using relativistic quantum chemical calculations, we show the existence of another stable isomer: the icosahedral “golden” fullerene Au 32 , the first all-gold fullerenic species. It is spherical and hollow (with a diameter of  0.9 nm) and structurally very similar to C 60 . Au 32 has a record value of magnetic shielding at its center, and appears to be aromatic. Considering its place in the periodic table, gold is an unusually relativistic element. [6] Among other things, this is expressed in its bonding properties. The element manifests aurophilicity, which further enhances the strong gold–gold interactions. [7] Relativistic effects make many interesting pure gold species such as clusters and nanotubes possible. In addition, heterogenic species are also studied with great interest. The bimetallic icosahedron WAu 12 , first predicted by Pyykkö and Runeberg [8] and later synthesized by Li et al., [9] is representative of these. Recently, images of multiwalled gold nanowires were published. [3] No reports of pure “golden” fullerenes exist, however. The closest match is WAu 12 , where the Au 12 shell engulfs a tungsten atom. The icosahedral form of Au 12 is itself, however, unstable. [10] Few studies of Au 32 exist. Work with empirical potentials suggest that the global energy minimum for the molecule is a low-symmetry, lumplike structure of either C 2 [4] or D 2 sym- metry. [5] The scalar relativistic density functional theory (DFT) calculations presented here show that Au 32 has another minimum: the icosahedral fullerenic form. To determine the stability of the Au 32 fullerene, we first optimized its structure. Two different functionals, the popular generalized gradient approximation (GGA) functional BP86 [11] and the nonempir- ical hybrid GGA functional PBE0, [12] were used throughout this work. Au 32 is composed of triangles in icosahedral symmetry, making a near perfect rhombic triacontahedron. Each atom binds to either five or six neighboring gold atoms. Thus, the symmetry is the same as for the truncated icosahedron C 60 , with the vertices and planes interchanged. Figure 1 shows the structure of Au 32 , compared with C 60 . Au 32 is a closed-shell molecule with an appreciable energy gap between the frontier orbitals, factors important for stability. The gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is 1.7 and 2.5 eV as calculated with the BP86 and PBE0 functionals, respectively. The high symmetry of the molecule increases the density of states in the frontier orbital region; both the HOMO and LUMO are fourfold degenerate. The harmonic vibrational frequencies of the optimized molecular structure show the icosahedral form to be a minimum; no imaginary frequencies were obtained. A sta- tionary point on the potential energy surface (PES) does not Figure 1. The molecular structures of the Au 32 (above) and C 60 (below) fullerenes. The calculated Au Au bond lengths vary between 276 and 287 pm. The figure was prepared using the gOpenMol package. [32] [*] M. P. Johansson, Dr. D. Sundholm Laboratory for Instruction in Swedish Department of Chemistry, University of Helsinki P.O. Box 55, 00014 Helsinki (Finland) Fax: (+ 358)9-191-50169 E-mail: mikael.johansson@helsinki.fi Dr. J. Vaara Laboratory of Physical Chemistry Department of Chemistry, University of Helsinki P.O. Box 55, 00014 Helsinki (Finland) [**] We thank Prof. P. Pyykkö and M. Patzschke for inspiring discus- sions. D.S. and M.P.J. thank Prof. R. Ahlrichs for a copy of TURBOMOLE. CSC-Scientific Computing Ltd. provided ample computing time. This work was supported by the Magnus Ehrnrooth Foundation, the Emil Aaltonen Foundation, Waldemar von Frenckells stiftelse, and The Academy of Finland. Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Communications 2678 # 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/anie.200453986 Angew. Chem. Int. Ed. 2004, 43, 2678 –2681