A rare case of a zero-field single-ion magnet in a cerium(III) pseudo-icosahedral complex
Jarrod R Thomas1, Marcus J Giansiracusa2, Jonathan T Mifsud1
1School of Chemistry, The University of New South Wales (UNSW), Kensington, Sydney, 2052, Australia. s.sulway@unsw.edu.au.
Abstract:
The synthesis and structural characterisation of [Ln(Tp2-Fu)2]I (1-Ln; Ln = La, Ce, Pr, Nd) (Tp2-Fu = hydrotris(3-(2'-furyl)-pyrazol-1-yl)borate) have been reported as an isomorphous series adopting pseudo-icosahedral ligand field geometries. Continuous shape measurement (CShM) analyses on the crystal field environments of 1-Ln show the smallest values yet reported for complexes employing two hexadentate ligands (e.g. bis-scorpionate environments), with the smallest belonging to 1-La. Single-ion magnetism for 1-Ce, 1-Pr and 1-Nd was probed with ac magnetic susceptibility studies revealing slow magnetic relaxation for 1-Nd in applied magnetic fields and in zero-applied field for 1-Ce, which is a rare observation for Ce(III)-based single-ion magnets. The energy barrier to magnetic relaxation for 1-Ce was experimentally determined to be Ueff = 30(5) cm-1, which is comparable to that of other cerium-based single-molecule magnets in the literature, where these systems stablise the m = ±5/2 state and possess large energy gaps between the ground and first excited state that do not agree with the experimentally determined barrier.
Related Concept Videos
03:26Electron Configuration of Multielectron Atoms
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:42Valence Bond Theory
01:30Paramagnetism