Realization of Organocerium-Based Fullerene Molecular Materials Showing Mott Insulator-Type Behavior
Electron-rich organocerium complexes (C5Me4H)(3)Ce and [(C5Me5)(2)Ce(ortho-oxa)], with redox potentials E-1/2 = -0.82 V and E-1/2 = -0.86 V versus Fc/Fc(+), respectively, were reacted with fullerene (C-60) in different stoichiometries to obtain molecular materials. Structurally characterized cocrystals: (C5Me4H)(3)Ce<middle dot>C-60 (1) and (C5Me5)(2)Ce(ortho-oxa)<middle dot>C-60 (2) of C-60 with cerium-based, molecular rare earth precursors are reported for the first time. The extent of charge transfer in 1 and 2 was evaluated using a series of physical measurements: FT-IR, Raman, solid-state UV-vis-NIR spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and magnetic susceptibility measurements. The physical measurements indicate that 1 and 2 comprise the cerium(III) oxidation state, with formally neutral C-60 as a cocrystal in both cases. Pressure-dependent periodic density functional theory calculations were performed to study the electronic structure of 1. Inclusion of a Hubbard-U parameter removes Ce f states from the Fermi level, opens up a band gap, and stabilizes FM/AFM magnetic solutions that are isoenergetic because of the large distances between the Ce(III) cations. The electronic structure of this strongly correlated Mott insulator-type system is reminiscent of the well-studied Ce2O3.
WOS:001192385500001
2024-03-27
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Funder | Grant Number |
Basic Energy Sciences | DE-SC0020169 |
Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Materials and Chemical Sciences Research for Quantum Information Science Program of the U.S. Department of Energy | |
Vagelos Institute for Energy Science and Technology for the graduate fellowship | DE-SC0020340 |
U.S. Department of Energy, Office of Science, Fusion Energy Sciences award entitled High Energy Density Quantum Matter | |
University of Pennsylvania | |
U.S. Department of Energy (DOE) | DE-SC0020169 |