Sections
Personal tools
 

Spectroelectrochemistry

The studies of the molecules' response to the charge transfer by electrochemisrty and Vis-NIR/ESR spectroelectrochemistry give valuable information on the electronic properties. In close connection with the Center of Spectroelectrochemistry, we perform both experimental and theoretical studies of the charged states of endohedral metallofullerenes, their derivatives as well as derivatives of empty fullerenes. In the studies of EMFs, we are especially interested in the endohedral redox systems. In such molecules, electron transfer occurs "through" the carbon cage and changes the valence state of endohedral atoms. For instance, endohedral redox activity was recently discovered in CeLu2N@C80 (Ce(III) can be oxidized to Ce(IV)) and in TiSc2N@C80 (here Ti is active both in reduction and oxidation changing its oxidation state form Ti(II) to Ti(IV)). For Sc3N@C80 and its derivatives, 45-Sc hyperfine structure of ESR spectra of the anions gives rich information on the role of the cluster in the frontier molecular orbitals. For perfluoroalkylated fullerenes, our studies revealed correlations between addition patterns, localization of the LUMO, and reduction potentials. Localization of the LUMOs is also studied via 19-F hyperfine structure in ESR spectra C60,70(CF3)2n radical-anions.

 

For details on experimental equipment, see Center of Spectroelectrochemistry

 

Electrochemical and spectroelectrochemical studies of endohedral metallofullerenes

    ScCF3-cover        CeLu-cover

 ScCF3-ESR

(a) DFT-computed spin density distribution in the anion-radical Sc3N@C80−. and its CF3-derivatives;

(b-e) experimental and simulated ESR spectra of the anions-radicals Sc3N@C80(CF3)2−. (b), Sc3N@C80(CF3)23−. (c), Sc3N@C80(CF3)10−. (d), and Sc3N@C80(CF3)12−. (e).


Selected publications:

  1.  A. A. Popov, N. B. Shustova, A. L. Svitova, M. A. Mackey, C. E. Coumbe, J. P. Phillips, S. Stevenson, S. H. Strauss, O. V. Boltalina, L. Dunsch. Redox tuning endohedral fullerene spin states. From the dication to the trianion radical of Sc3N@C80(CF3)2 in five reversible single-electron steps. Chem. Eur. J. 2010, 16 (16), 4721-4724. DOI: 10.1002/chem.201000205. Inside cover DOI: 10.1002/chem.201090074
  2. L. Zhang, A. A. Popov, S. Yang, S. Klod, P. Rapta, L. Dunsch. An endohedral redox system in a fullerene cage: the Ce based mixed-metal cluster fullerene Lu2CeN@C80. Phys. Chem. Chem. Phys. 2010, 12, 7840-7847. DOI: 10.1039/c002918a. Inside cover DOI: 10.1039/C0CP90047H.
  3. 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/nn101115d
  4. 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
  5. 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
  6. P. Rapta, A. A. Popov, S. Yang, L. Dunsch. The Charged States of Sc3N@C68: An in situ Spectroelectrochemical Study of the Radical Cation and Radical Anion of a Non-IPR Fullerene. J. Phys. Chem. A 2008, 112 (26), 5858-5865. DOI: 10.1021/jp802655f

 

Electrochemical and spectroelectrochemical studies of empty fullerenes' derivatives

C60CF3-6_ESR

Experimental and simulated ESR spectra of C60(CF3)6−. radical anion (left) and its DFT-computed spin density (right). To simlate the ESR spectrum, hypefine coupling connstants computed at the DFT leve (B3LYP/aug-cc-pCVTZ) were used as initial guess for a fitting procedure.

 C60CF3-LUMO

The first reduction potential in a series of C60(CF3)2n derivatives plotted as a function of DFT-predicted LUMO energy (compounds are labelled by two numbers, the first щту shows the number of CF3 groups, the second one shows the number of the isomer). The inset shows the same potential plotted versus the number of CF3 groups. As can be seen, reduction potential exhibits virtually now dependence on the number of groups, but strongly depends on the addition pattern (for the isomers with the same number of attached groups, reduction potentials span the range up to 0.5 V).

 Selected publications:

  1. A. A. Popov, I. E. Kareev, N. B. Shustova, S. H. Strauss, O. V. Boltalina, L. Dunsch. Unraveling the Electron Spin Resonance Pattern of Nonsymmetric Radicals with 30 Fluorine Atoms: Electron Spin Resonance and Vis−Near-Infrared Spectroelectrochemistry of the Anion Radicals and Dianions of C60(CF3)2n (2n = 2–10) Derivatives and Density Functional Theory-Assisted Assignment. J. Am. Chem. Soc. 2010, 132 (33), 11709-11721. DOI: 10.1021/ja1043775
  2. A. A. Popov, N. B. Shustova, O. V. Boltalina, S. H. Strauss, L. Dunsch. ESR-Vis/NIR Spectroelectrochemical Study of C70(CF3)2−. and C70(C2F5)2−. Radical Anions. ChemPhysChem 2008, 9 (3), 431-438. DOI: 10.1002/cphc.200700708
  3. A. A. Popov, I. E. Kareev, N. B. Shustova, S. F. Lebedkin, S. H. Strauss, O. V. Boltalina, L. Dunsch. Synthesis, Spectroscopic and Electrochemical Characterization, and DFT Study of Seventeen C70(CF3)n Derivatives (n = 2, 4, 6, 8, 10, 12). Chem. Eur. J. 2007, 14 (1), 107-121. DOI: 10.1002/chem.200700970
  4. A. A. Popov, I. E. Kareev, N. B. Shustova, E. B. Stukalin, S. F. Lebedkin, K. Seppelt, S. H. Strauss, O. V. Boltalina, L. Dunsch. Electrochemical, Spectroscopic, and DFT Study of C60(CF3)n Frontier Orbitals (n = 2-18): The Link between Double Bonds in Pentagons and Reduction Potentials. J. Am. Chem. Soc. 2007, 129 (37), 11551-11568. DOI: 10.1021/ja073181e
  5. A. A. Popov, J. Tarabek, I. E. Kareev, S. F. Lebedkin, S. H. Strauss, O. V. Boltalina, L. Dunsch. Poly(trifluoromethyl)fullerene Radical Anions. An ESR/Vis-NIR Spectroelectrochemical Study of C60F2,4 and C60(CF3)2,10. J. Phys. Chem. A 2005, 109 (43), 9709-9711. DOI: 10.1021/jp0550006