Quantum chemical computations of fullerenes and their derivaties

Endohedral metallofullerenes:

Selected publications

Endohedral metallofullerenes synhtesized in IFW Dresden, whose structures were determined with the help of DFT computations

For details on synthesis of EMFs in IFW Dresden, see Synthesis of Nanomaterials

The figure plots normalized energy (per carbon atom) for the most stable hexaanions of fullerenes C_2n versus the number of carbon atoms. Smooth decrease of the energy is observed (because of the decrease of the on-site Coulomb repulsion and steric strain with the increase of the cage size). However, C₈₀-I_h shows significant deviation from the curve pointing to the enhanced stability of this cage isomer in the hexaanionic state. As a result, if an endohedral cluster transfers six electron to the fullerene (such as M₃N, Sc₄C₂, La₂, etc), C₈₀-I_h isomer is obtained in much higher yield than all other structures.  Note that to find the most stable isomers for each 2n, extensive computations with consideration of up to 20000 isomers were performed.

The figure plots the number of non-IPR isomers and IPR isomers among the 10 most stable C_2n^6- structures for each 2n. The stuctures with different number of adjacent pentagon pairs (APPs) is shown by different colors. For IPR isomer, total number of possible isomers for given 2n is listed The non-IPR isomers can compete in stability with IPR structres up to C₈₄: for relatively small cages (2n<72), 3 APPs are preferable; the structures with two APPs are dominating among the most stable isomers for C₇₂-C₇₈; the isomers with one APP can be expected for C₈₀-C₈₄; for the larger cages, formation of non-IR isomers is not expected, IPR isomers are much more stable.

Selected publications.

Derivatives of empty fullerenes:

Selected publications

¹⁹F NMR spectroscopy of CF₃-derivatives of fullerenes can give information on the relative position of CF₃ groups, but exact addition patterns still remain unclear. Using ¹⁹F NMR data to reduce the number of possible isomers and applying extended computations at the AM1 and DFT levels of theory, we are able to determine molecular structures of CF₃-derivatives with very high degree of certainty comparable to that of single-crystal X-ray diffraction studies (in fact, many structures wich were first determined by NMR/DFT studies, were then confirmed by X-ray). The figure above shows addition patterns of several CF₃ derivatives of "insoluble" higher fullerenes determined by NMR/DFT studies. Importantly, such "insoluble" fullerenes remain in the soot after standard extraction procedure and hence cannot be characterized. However, they can be solubilized by trifuoromethylation thus making their further structural characterization possible. Our study proved that some fullerene isomers are indeed formed in the arc-discharge process (C₇₄-D_3h, C₇₆-T_d, C₇₈-D_3h(5)), even though they have been never characterized in the pristine underivatized form.

The studies of the fullerene derivatives are performed in close collaboration with Strauss/Boltalina research group in Colorado State University (Fort Collins, USA)

 Selected publications

Derivatives of endohedral metallofullerenes:

1.  N. B. Shustova, D. V. Peryshkov, I. V. Kuvychko, Y.-S. Chen, M. A. Mackey, C. E. Coumbe, D. T. Heaps, B. S. Confait, T. Heine, J. P. Phillips, S. Stevenson, L. Dunsch, A. A. Popov, S. H. Strauss, O. V. Boltalina. Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc₃N@C₈₀(CF₃)_n (n = 2−16) and Their Radical Anions. J. Am. Chem. Soc. 2011, 133 (8), 2672–2690. DOI: 10.1021/ja109462j
2. N. B. Shustova, Y.-S. Chen, M. A. Mackey, C. E. Coumbe, J. P. Phillips, S. Stevenson, A. A. Popov, O. V. Boltalina, S. H. Strauss. Sc₃N@(C₈₀-I_h(7))(CF₃)₁₄ and Sc₃N@(C₈₀-I_h(7))(CF₃)₁₆. Endohedral Metallofullerene Derivatives with Exohedral Addends on Four and Eight Triple-Hexagon Junctions. Does the Sc₃N Cluster Control the Addition Pattern or Vice Versa? J. Am. Chem. Soc. 2009, 131 (48), 17630-17637. DOI: 10.1021/ja9069216
3. N. B. Shustova, A. A. Popov, M. A. Mackey, C. E. Coumbe, J. P. Phillips, S. Stevenson, S. H. Strauss, O. V. Boltalina. Radical Trifluoromethylation of Sc₃N@C₈₀. J. Am. Chem. Soc. 2007, 129 (38), 11676-11677. DOI: 10.1021/ja074332g

Boranes:

Computational studies of boranes are performed in close collaboration with Strauss/Boltalina research group in Colorado State University (Fort Collins, USA)

1. D. Peryshkov, A. A. Popov, S. H. Strauss. Latent Porosity in Potassium Dodecafluoro-closo-dodecaborate(2−). Structures and Rapid Room Temperature Interconversions of Crystalline K₂B₁₂F₁₂, K₂(H₂O)₂B₁₂F₁₂, and K₂(H₂O)₄B₁₂F₁₂ in the Presence of Water Vapor. J. Am. Chem. Soc. 2010, 132 (39), 13902-13913. DOI: 10.1021/ja105522d
2. D. V. Peryshkov, A. A. Popov, S. H. Strauss. Direct Perfluorination of K₂B₁₂H₁₂ in Acetonitrile Occurs at the Gas Bubble−Solution Interface and Is Inhibited by HF. Experimental and DFT Study of Inhibition by Protic Acids and Soft, Polarizable Anions. J. Am. Chem. Soc. 2009, 131 (51), 18393-18403. DOI: 10.1021/ja9069437
3. Y. Kobayashi, A. A. Popov, S. M. Miller, O. P. Anderson, S. H. Strauss. Synthesis and Structure of Ag(1-Me-12-SiPh₃-CB₁₁F₁₀): Selective F12 Substitution in 1-Me-CB₁₁F₁₁^- and the First Ag(arene)₄⁺ Tetrahedron. Inorg. Chem. 2007, 46 (21), 8505-8507. DOI: 10.1021/ic701606p
4. Y. Kobayashi, S. V. Ivanov, A. A. Popov, S. M. Miller, O. P. Anderson, K. A. Solntsev, S. H. Strauss. Tetrabutylammonium salt of the B₂₄F₂₂^4– anion. Two B₁₂F₁₁^2– icosahedra linked by a 2c-2e B-B bond and surrounded by a sheath of CH· · ·FB hydrogen bonds. Heteroatom Chemistry 2006, 17 (3), 181-187. DOI: 10.1002/hc.20220