TY - JOUR
T1 - Effect of Axial Ligands on Easy-Axis Anisotropy and Field-Induced Slow Magnetic Relaxation in Heptacoordinated FeII Complexes
AU - Mondal, Arpan
AU - Wu, Shu Qi
AU - Sato, Osamu
AU - Konar, Sanjit
N1 - Funding Information:
A.M. thanks the IISER Bhopal for an SRF fellowship and S.K. thanks the CSIR (project no. 01(2974)/19/EMR‐II), the Government of India, and the IISER Bhopal for generous financial support. A.M. and S.K. also thank Dr. R. S. Singh, Department of Physics, IISER Bhopal, for performing the XPS measurements. The staff of the high‐performance computing (HPC) facility at IISER Bhopal is gratefully acknowledged for facilitating the computational work.
Publisher Copyright:
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/4/9
Y1 - 2020/4/9
N2 - A rational approach to modulating easy-axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated FeII complexes has been explored. In this series of complexes with formulae of [Fe(H4L)(NCS)2]⋅3 DMF⋅0.5 H2O (1), [Fe(H4L)(NCSe)2]⋅3 DMF⋅0.5 H2O (2), and [Fe(H4L)(NCNCN)2]⋅DMF⋅H2O (3) [H4L=2,2′-{pyridine-2,6-diylbis(ethan-1-yl-1-ylidene)}bis(N-phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen-based π-donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy-axis magnetic anisotropy for all of the complexes, with 1 [Ueff=21 K, τ0=1.72×10−6 s] and 2 [Ueff=25 K, τ0=2.25×10−6 s] showing field-induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts.
AB - A rational approach to modulating easy-axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated FeII complexes has been explored. In this series of complexes with formulae of [Fe(H4L)(NCS)2]⋅3 DMF⋅0.5 H2O (1), [Fe(H4L)(NCSe)2]⋅3 DMF⋅0.5 H2O (2), and [Fe(H4L)(NCNCN)2]⋅DMF⋅H2O (3) [H4L=2,2′-{pyridine-2,6-diylbis(ethan-1-yl-1-ylidene)}bis(N-phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen-based π-donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy-axis magnetic anisotropy for all of the complexes, with 1 [Ueff=21 K, τ0=1.72×10−6 s] and 2 [Ueff=25 K, τ0=2.25×10−6 s] showing field-induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts.
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U2 - 10.1002/chem.201905166
DO - 10.1002/chem.201905166
M3 - Article
C2 - 31943399
AN - SCOPUS:85082762653
SN - 0947-6539
VL - 26
SP - 4780
EP - 4789
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 21
ER -