Magnetic Relaxation in Single-Electron Single-Ion Cerium(III) Magnets: Insights from Ab Initio Calculations.
Detailed ab initio calculations were performed on two structurally different cerium(III) single-molecule magnets (SMMs) to probe the origin of magnetic anisotropy and to understand the mechanism of magnetic relaxations. The complexes [Ce(III){Zn(II)(L)}2(MeOH)]BPh4 (1) and [Li(dme)3][Ce(III)(cot'')2] (1; L=N,N,O,O-tetradentate Schiff base ligand; 2; DME=dimethoxyethane, COT''=1,4-bis(trimethylsilyl)cyclooctatetraenyldianion), which are reported to be zero-field and field-induced SMMs with effective barrier heights of 21.2 and 30 K respectively, were chosen as examples. CASSCF+RASSI/SINGLE_ANISO calculations unequivocally suggest that mJ|±5/2〉 and |±1/2〉 are the ground states for complexes 1 and 2, respectively. The origin of these differences is rooted back to the nature of the ligand field and the symmetry around the cerium(III) ions. Ab initio magnetisation blockade barriers constructed for complexes 1 and 2 expose a contrasting energy-level pattern with significant quantum tunnelling of magnetisation between the ground state Kramers doublet in complex 2. Calculations performed on several model complexes stress the need for a suitable ligand environment and high symmetry around the cerium(III) ions to obtain a large effective barrier.
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 (India).
Saurabh Kumar
SK
Singh
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 (India).
Tulika
T
Gupta
Division of Quantum and Physical Chemistry, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F 3001 Heverlee, Leuven (Belgium). liviu.ungur@chem.kuleuven.be.
Liviu
L
Ungur
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 (India). rajaraman@chem.iitb.ac.in.
Gopalan
G
Rajaraman
cerium; density functional calculations; ligand effects; magnetic properties