Abstract
Three 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.
Original language | English |
---|---|
Pages (from-to) | 12603-12617 |
Number of pages | 15 |
Journal | Inorganic Chemistry |
Volume | 55 |
Issue number | 24 |
DOIs | |
State | Published - Dec 19 2016 |
Funding
We are grateful for financial support from the National Basic Research Program of China (No. 2013CB922102 to X.-T.C. and Y.S.), the Natural Science Grant of China (No. 21471078 to X.-T.C.), the Natural Science Foundation of Jiangsu Province of China (BK20151542), and the U.S. National Science Foundation (CHE-1362548 and CHE-1633870 to Z.-L.X.). Acknowledgment is also made to the donors of the American Chemical Society Petroleum Research Fund for partial support of this research.
Funders | Funder number |
---|---|
Natural Science Grant of China | 21471078 |
U.S. National Science Foundation | CHE-1633870, CHE-1362548 |
National Science Foundation | 1633870, 1362548 |
American Chemical Society Petroleum Research Fund | |
Natural Science Foundation of Jiangsu Province | BK20151542 |
National Basic Research Program of China (973 Program) | 2013CB922102 |