Design of new anionic, anion-radical and coordination compounds of endometallo- and endometallonitrides of fullerenes with perspective magnetic and conducting properties

• Applicant: Dr. Alexey A. Popov
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation ; Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 386027243

• Final Report Year: 2021

Final Report Abstract

The project was aimed at a better understanding of the structural and electronic properties of endohedral metallofullerenes (EMFs), particularly in their anionic forms, and was performed in collaboration with the Institute of Problems of Chemical Physics of the Russian Academy of Science (Chernogolovka, Moscow region; IPCP hereafter). The main achievements of the project performed included (1) the synthesis of magnetic and non-magnetic EMFs and characterization of their anionic states; (2) structural and spectroscopic studies of EMF crystals; (3) the studies of magnetic properties of EMFs. Series of nitride clusterfullerenes (NCFs) with different metals were synthesized. A systematic exploration of the synthesis of mixed-metal Dy-M nitride clusterfullerenes (NCFs, M = Gd, Er, Tm, Lu) was performed, and the factors affecting the relative yields of mixed-metal species were determined. The compounds were isolated by chromatography, characterized by single-crystal X-ray diffraction, and studied by SQUID magnetometry, with a particular focus on single-molecule magnetism. Molecular structure and dynamics of Sc3N@C70 in the crystal were studied by variable-temperature single-crystal X-ray diffraction. Dimetallofullerenes with single-electron metal-metal bonds formed another group of EMFs comprehensively studies in the project. We synthesized a series of M2@C80(CH2Ph) compounds (M2 = Gd2, Tb2, Ho2, Er2, Sc2, TbY, and TbGd) and studied their magnetic and redox properties. Di-EMFs with Dy and Tb were found to be single-molecule magnets with high blocking temperatures of magnetization and broad magnetic hysteresis. These properties could be attributed to the exceptionally strong exchange interaction between lanthanide ions mediated by unpaired electron residing on the M-M bonding orbital. This orbital was shown to be redox-active. In particular, electrochemical or chemical reduction of M2@C80(CH2Ph) species was demonstrated to proceed via population of the M-M orbital with the second electrons, leading to a strong metal dependence of reduction potentials. Stable anions could be obtained in solutions, and changes of their magnetic properties with respect to neutral compounds demonstrated that di-EMFs represent a special class of magnetic redox switches.

Publications

• "Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal-metal bond." Nat. Commun. 2019, 10, 571
  F. Liu, G. Velkos, D. S. Krylov, L. Spree, M. Zalibera, R. Ray, N. A. Samoylova, C.-H. Chen, M. Rosenkranz, S. Schiemenz, F. Ziegs, K. Nenkov, A. Kostanyan, T. Greber, A. U. B. Wolter, M. Richter, B. Büchner, S. M. Avdoshenko, A. A. Popov
  
• "Mixed dysprosium-lanthanide nitride clusterfullerenes DyM2N@C80-Ih and Dy2MN@C80-Ih (M = Gd, Er, Tm, and Lu): synthesis, molecular structure, and quantum motion of the endohedral nitrogen atom." Nanoscale 2019, 11, 13139-13153
  C. Schlesier, F. Liu, V. Dubrovin, L. Spree, B. Büchner, S. M. Avdoshenko, A. A Popov
  
• "Mixed dysprosium-lanthanide nitride clusterfullerenes DyM2N@C80-Ih and Dy2MN@C80-Ih (M = Gd, Er, Tm, and Lu): synthesis, molecular structure, and quantum motion of the endohedral nitrogen atom." Nanoscale 2019, 11, 13139-13153
  C. Schlesier, F. Liu, V. Dubrovin, L. Spree, B. Büchner, S. M. Avdoshenko, A. A Popov
  
• "Molecular structure, magnetic and optical properties of endometallonitridofullerene Sc3N@Ih‐C80 in neutral, radical anion and dimeric anionic forms." Chem. Eur. J. 2019, 25 (65), 14858-14869
  D. Konarev, A. A. Popov, L. V. Zorina, S. S. Khasanov, R. N. Lyubovskaya
  
• "Single-electron lanthanidelanthanide bonds inside fullerenes towards robust redox-active molecular magnets." Acc. Chem. Res. 2019, 52 (10), 2981-2993
  F. Liu, L. Spree, D. S. Krylov, G. Velkos, S. M. Avdoshenko, A. A. Popov
  
• "Caught in Phase Transition: Snapshot of the Metallofullerene Sc3N@C70 Rotation in the Crystal." J. Am. Chem. Soc. 2021, 143 (2), 612–616
  Y. Hao, Y. Wang, V. Dubrovin, S. M. Avdoshenko, A. A. Popov, F. Liu