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Structural Tailoring Effects on the Magnetic Behavior of Symmetric and Asymmetric Cubane‐Type Ni complexes
Author(s) -
Ponomaryov Alexey N.,
Kim Namseok,
Hwang Jaewon,
Nojiri Hiroyuki,
van Tol Johan,
Ozarowski Andrew,
Park Jena,
Jang Zeehoon,
Suh Byoungjin,
Yoon Sungho,
Choi KwangYong
Publication year - 2013
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201300054
Subject(s) - cubane , electron paramagnetic resonance , chemistry , steric effects , hysteresis , paramagnetism , magnetization , crystallography , magnetic hysteresis , magnetic susceptibility , condensed matter physics , magnetic field , nuclear magnetic resonance , stereochemistry , crystal structure , physics , quantum mechanics
Using two kinds of carboxylate ligands with small but significant differences in steric size, symmetric and asymmetric Fe II and Ni II cubanes have been synthesized in a controlled fashion. Fast sweeping pulsed field measurements showed magnetization hysteresis loops for two cubane‐type molecular complexes, [Ni 4 (μ‐OMe) 4 (O 2 CAr 4F‐Ph ) 4 (HOMe) 8 ] and [Ni 4 (μ‐OMe) 4 (O 2 CAr Tol ) 4 (HOMe) 6 ], thus suggesting single‐molecule magnet behavior. To differentiate the magnetic properties between the symmetric and asymmetric cubanes, detailed electron paramagnetic resonance (EPR) measurements were performed. From the EPR data, taken at various frequencies and temperatures, zero‐field splitting parameters D , E , and other higher‐order parameters for both cubane samples were extracted. Compared to the symmetric Ni‐cubane, the asymmetric one shows an increase in the D and E values by about 20 %, thereby suggesting structural engineering effects on the magnetic properties. By using the magnetic parameters determined by EPR, a static magnetization curve at 2 K and a temperature dependence of the magnetic susceptibility were simulated. A good agreement between theoretical and experimental data confirms the validity of the values obtained from EPR measurements.