TY - JOUR
TI - Magnetic Properties and Electronic Structure of the S = 2 Complex [MnIII(OPPh2)2N3] Showing Field-Induced Slow Magnetization Relaxation
AU - Sanakis, Y.
AU - Krzystek, J.
AU - Maganas, D.
AU - Grigoropoulos, A.
AU - Ferentinos, E.
AU - Kostakis, M.G.
AU - Petroulea, V.
AU - Pissas, M.
AU - Thirunavukkuarasu, K.
AU - Wernsdorfer, W.
AU - Neese, F.
AU - Kyritsis, P.
JO - ISRN Inorganic Chemistry
PY - 2020
VL - 59
TODO - 18
SP - 13281-13294
PB - American Chemical Society
SN - 2314-470X
TODO - 10.1021/acs.inorgchem.0c01636
TODO - Calculations;  Chlorine compounds;  Computation theory;  Electron spin resonance spectroscopy;  Electronic properties;  Electronic structure;  Gallium compounds;  Ground state;  Hysteresis;  Hysteresis loops;  Magnetic fields;  Magnetic materials;  Magnetic susceptibility;  Magnetization;  Paramagnetic resonance;  Quantum chemistry;  Relaxation processes;  Single crystals;  Spectroscopic analysis;  Spin orbit coupling;  SQUIDs;  Wave functions, Electron paramagnetic resonances (EPR);  External magnetic field;  Ground state wavefunctions;  Magnetic and electronic properties;  Magnetization relaxation;  Quantum chemical calculations;  Quantum tunneling of magnetization;  Spin Hamiltonian parameters, Manganese compounds
TODO - The high-spin S = 2 Mn(III) complex [Mn(OPPh2)2N3] (1Mn) exhibits field-induced slow relaxation of magnetization (Inorg. Chem. 2013, 52, 12869). Magnetic susceptibility and dual-mode X-band electron paramagnetic resonance (EPR) studies revealed a negative value of the zero-field-splitting (zfs) parameter D. In order to explore the magnetic and electronic properties of 1Mn in detail, a combination of experimental and computational studies is presented herein. Alternating-current magnetometry on magnetically diluted samples (1Mn/1Ga) of 1Mn in the diamagnetic gallium analogue, [Ga(OPPh2)2N3], indicates that the slow relaxation behavior of 1Mn is due to the intrinsic properties of the individual molecules of 1Mn. Investigation of the single-crystal magnetization of both 1Mn and 1Mn/1Ga by a micro-SQUID device reveals hysteresis loops below 1 K. Closed hysteresis loops at a zero direct-current magnetic field are observed and attributed to fast quantum tunneling of magnetization. High-frequency and-field EPR (HFEPR) spectroscopic studies reveal that, apart from the second-order zfs terms (D and E), fourth-order terms (B4m) are required in order to appropriately describe the magnetic properties of 1Mn. These studies provide accurate spin-Hamiltonian (sH) parameters of 1Mn, i.e., zfs parameters |D| = 3.917(5) cm-1, |E| = 0.018(4) cm-1, B04 = B42 = 0, and B44 = (3.6 ± 1.7) × 10-3 cm-1 and g = [1.994(5), 1.996(4), 1.985(4)], and confirm the negative sign of D. Parallel-mode X-band EPR studies on 1Mn/1Ga and CH2Cl2 solutions of 1Mn probe the electronic-nuclear hyperfine interactions in the solid state and solution. The electronic structure of 1Mn is investigated by quantum-chemical calculations by employing recently developed computational protocols that are grounded on ab initio wave function theory. From computational analysis, the contributions of spin-spin and spin-orbit coupling to the magnitude of D are obtained. The calculations provide also computed values of the fourth-order zfs terms B4m, as well as those of the g and hyperfine interaction tensor components. In all cases, a very good agreement between the computed and experimentally determined sH parameters is observed. The magnetization relaxation properties of 1Mn are rationalized on the basis of the composition of the ground-state wave functions in the absence or presence of an external magnetic field. © 2020 American Chemical Society.
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