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Chemical Bonding

Electronic structure of endohedral metallofullerenes is usually described as a result of the electron transfer from metal atoms to the carbon cage with purely ionic bonding. Although this description enables explanation of many properties of EMFs (such as carbon cage isomerism), it is oversimplified. There is also a significant covalent component in the metal-cage bonding. We study these phenomena applying topological analysis of the electronic density (Bader's quantum theory of atoms-in-molecules, QTAIM) or electron localization function (ELF). For Y3@C80, topological analysis also revealed a non-nuclear attractor (maximum of the electron density, i.e. a "pseudoatom")

NNA

Molecular graphs of Y3@C80 (left) and Y3N@C80 (right). Yttrium atoms are violet, carbon atoms are gray or pink (if bonded to Y); bond, ring, and cage critical points are red, yellow, and green, respectively. Bader volumes of the non-nuclear attractor in Y3@C80 and the nitrogen atom in Y3N@C80 are shown in blue.

  

 ELF


Spatial distribution of electron localization function (ELF):

(a-d) ELF (isovalue 0.72) in Y3@C80+ (a, b), Y2@C82 (c) and Y3N@C80 (d);

color code for basins: yellow – valence disynaptic V(C,C) basins, light green – core C(C) basins, light blue – valence trisynaptic V(Y,C,C), basins orange – core C(Y), dark blue/green –  valence V(Y,Y,Y), V(Y,Y) and V(N,Y,Y); valence V(C,C) and core C(C) basins are not shown in (b-d);

(d-f) Enlarged view of ELF in the Y3 (e) and Y3N (f) clusters; one V(Y,Y,Y) for Y3 and two V(N,Y,Y) basins for Y3N are not shown;

(g-h) 2D map of ELF in Y3@C80+ (g) and Y3N@C80 (h) in the plane of the yttrium atoms. Shell structure of the N and Y atoms can be clearly seen.

 

Publications:

  1. 1. L. Dunsch, S. Yang, L. Zhang, A. Svitova, S. Oswald, A. A. Popov. Metal Sulfide in a C82 Fullerene Cage: A New Form of Endohedral Clusterfullerenes. J. Am. Chem. Soc. 2010, 132, 5413-5421. DOI: 10.1021/ja909580j
  2. A. A. Popov, C. Chen, S. Yang, F. Lipps, L. Dunsch. The Spin-Flow Vibrational Spectroscopy of Molecules with Flexible Spin Density: Electrochemistry, ESR, Cluster and Spin Dynamics, and Bonding in TiSc2N@C80. ACS Nano 2010, 4 (8), 4857-4871. DOI: 10.1021/nn101115
  3. A. A. Popov, L. Zhang, L. Dunsch. A pseudoatom in a cage: trimetallofullerene Y3@C80 mimics Y3N@C80 with nitrogen substituted by a pseudoatom. ACS Nano 2010, 4(2), 795-802. DOI: 10.1021/nn901422z
  4. A. A. Popov, L. Dunsch. Bonding in Endohedral Metallofullerenes as Studied by Quantum Theory of Atoms in Molecules. Chem. Eur. J. 2009, 15 (38), 9707-9729. DOI: 10.1002/chem.200901045
  5. A. A. Popov. Metal-Cage Bonding, Molecular Structures and Vibrational Spectra of Endohedral Fullerenes: Bridging Experiment and Theory. J. Comput. Theor. Nanosci. 2009, 6 (2), 292-317 (review). DOI: 10.1166/jctn.2009.1037 ask for reprint
  6. A. A. Popov, L. Dunsch. Hindered Cluster Rotation and 45Sc Hyperfine Splitting Constant in Distonoid Anion-Radical Sc3N@C80−, and Spatial Spin-Charge Separation as a General Principle for Anions of Endohedral Fullerenes with Metal-Localized Lowest Unoccupied Molecular Orbital. J. Am. Chem. Soc. 2008, 130 (52), 17726-17742. DOI: 10.1021/ja804226a
  7. A. A. Popov, L. Dunsch. Structure, Stability, and Cluster-Cage Interactions in Nitride Clusterfullerenes M3N@C2n (M = Sc, Y; 2n = 68-98): a Density Functional Theory Study. J. Am. Chem. Soc. 2007, 129 (38), 11835-11549. DOI: 10.1021/ja073809l