Abstract
The high-spin CoII complex (PPh4)2[Co(N3)4] (Co-N3) has been investigated using advanced spectroscopic techniques [far-IR magneto-spectroscopy (FIRMS), high-frequency and high-field EPR (HFEPR), and inelastic neutron scattering (INS)] to study its zero-field-splitting (ZFS), giving spin-Hamiltonian (SH) parameters. The analysis of multi-frequency HFEPR reveals the easy-axis anisotropy with a D value of −10.39(5) cm−1 and a rhombic ratio (E/D) of 0.21(1). The magnetic properties have also been probed by direct-current (DC) magnetometry, suggesting minor differences in anisotropy from the previously reported polymorph (Co-N3′). Ligand-field theory (LFT) analysis indicates that the structures of Co-N3 and Co-N3′ are closer to D2d symmetry than other symmetries considered. Alternate-current (AC) susceptibility reveals slow magnetic relaxation under an applied field, indicating that Co-N3 is a field-induced single-ion magnet (SIM). While both Co-N3 and Co-N3′ were studied by DC magnetometry, one unusual aspect of the current work on Co-N3 is that advanced spectroscopies HFEPR, FIRMS, and INS were used to directly observe transitions between ZFS split states, giving accurate SH parameters.
| Original language | English |
|---|---|
| Pages (from-to) | 17084-17098 |
| Number of pages | 15 |
| Journal | New Journal of Chemistry |
| Volume | 49 |
| Issue number | 39 |
| DOIs | |
| State | Published - Oct 6 2025 |
Funding
The US National Science Foundation [CHE-2055499 and CHE2349345 to Z.-L. X. and DGE-2152159 for an NRT (Research Traineeship Program) fellowship to A. T. H.] is acknowledged for support of the research. Both DC and AC magnetic property studies were conducted in part by J. X. and R. J. supported by Grant No. DE-SC0024501 funded by the U.S. Department of Energy, Office of Science and in part by the Center for Nanophase Materials Sciences, which was sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. We thank Dr A. Ozarowski for his EPR software package SPIN and Prof Jesper Bendix, University of Copenhagen, for Ligfield software. Part of this work was performed at the National High Magnetic Field Laboratory, which was supported by NSF Cooperative Agreement No. DMR-2128556 and the State of Florida. Neutron scattering experiments were conducted at the VISION beamline at ORNL’s Spallation Neutron Source, which is supported by the Scientific User Facilities Division, Office of Basic Energy Sciences (BES), the U.S. Department of Energy (DOE), under Contract No. DE-AC0500OR22725 with UT Battelle, LLC. The authors thank Michael J. Jenkins and Miranda A. Phillips for assistance.