ic6b01544_si_003.cif (27.98 kB)
Slow Magnetic Relaxations in Cobalt(II) Tetranitrate Complexes. Studies of Magnetic Anisotropy by Inelastic Neutron Scattering and High-Frequency and High-Field EPR Spectroscopy
dataset
posted on 2016-12-06, 22:03 authored by Lei Chen, Hui-Hui Cui, Shelby E. Stavretis, Seth C. Hunter, Yi-Quan Zhang, Xue-Tai Chen, Yi-Chen Sun, Zhenxing Wang, You Song, Andrey A. Podlesnyak, Zhong-Wen Ouyang, Zi-Ling XueThree
mononuclear cobalt(II) tetranitrate complexes (A)2[Co(NO3)4] with different countercations, Ph4P+ (1), MePh3P+ (2), and Ph4As+ (3), have
been synthesized and studied by X-ray single-crystal diffraction,
magnetic measurements, inelastic neutron scattering (INS), high-frequency
and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations.
The X-ray diffraction studies reveal that the structure of the tetranitrate
cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while
the central Co(II) ion of 3 is in a distorted-dodecahedral
configuration. The sole magnetic transition observed in the INS spectroscopy
of 1–3 corresponds to the zero-field
splitting (2(D2 + 3E2)1/2) from 22.5(2) cm–1 in 1 to 26.6(3) cm–1 in 2 and
11.1(5) cm–1 in 3. The positive sign
of the D value, and hence the easy-plane magnetic
anisotropy, was demonstrated for 1 by INS studies under
magnetic fields and HF-EPR spectroscopy. The combined analyses of
INS and HF-EPR data yield the D values as +10.90(3),
+12.74(3), and +4.50(3) cm–1 for 1–3, respectively. Frequency- and temperature-dependent alternating-current
magnetic susceptibility measurements reveal the slow magnetization
relaxation in 1 and 2 at an applied dc field
of 600 Oe, which is a characteristic of field-induced single-molecule
magnets (SMMs). The electronic structures and the origin of magnetic
anisotropy of 1–3 were revealed by
calculations at the CASPT2/NEVPT2 level.
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Keywords
3 E 2seven-coordinate geometriestetranitrate cobalt anionD valueX-ray diffraction studiessusceptibility measurementsanisotropyHF-EPR dataINS studiesINS spectroscopyinelastic neutronmagnetization relaxationX-ray single-crystal diffractiontemperature-dependent alternating-current600 OecmInelastic Neutron ScatteringSMMhigh-field EPRdc fieldcalculationHF-EPR spectroscopyCoCASPTPh 4countercationHigh-Field EPR SpectroscopyD values2 exhibitdistorted-dodecahedral configurationMagnetic AnisotropyPh 4 Pfield-induced single-molecule magnets
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