| Autor: |
Yang EC; Department of Chemistry, Fu-Jen Catholic University Hsinchuang, New Taipei City 242062, Taiwan, Republic of China., Tsai YT; Department of Chemistry, Fu-Jen Catholic University Hsinchuang, New Taipei City 242062, Taiwan, Republic of China., Chang PY; National Synchrotron Radiation Research Center, Hsinchu 300092, Taiwan, Republic of China., Ozerov M; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Krzystek J; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Chien SY; Instrumentation Centre College of Science, National Taiwan University, Taipei 10617, Taiwan, Republic of China., He JX; Department of Chemistry, Fu-Jen Catholic University Hsinchuang, New Taipei City 242062, Taiwan, Republic of China., Kuo TS; Centre of National Taiwan Normal University, Taipei 11677, Taiwan, Republic of China., Sheu HS; National Synchrotron Radiation Research Center, Hsinchu 300092, Taiwan, Republic of China. |
| Abstrakt: |
In this study, we synthesized a new Co(II) complex, [NMe 4 ] 2 [Co(bpyO 2 ) 2 ] ( 1 ), using deprotonated 2,2'-bipyridine-6,6'-diol ligands (bpyO 2 2- ). This compound exhibits a significant zero-field splitting ( D ) value. The far-infrared magneto spectroscopy and high-frequency and field electron paramagnetic resonance (HFEPR) measurements indicated that compound 1 possesses D = -54.8 cm -1 and E ∼ 0 cm -1 . These findings were subsequently confirmed by other experimental data, including DC magnetic susceptibilities and variable temperature and variable magnetic field reduced magnetizations. Additionally, we conducted a series of AC magnetic susceptibility measurements to investigate the kinetics of magnetization relaxation. Below 6.6 K and under zero external magnetic field, fast quantum tunneling of magnetization (QTM) dominates (∼570 Hz), and temperature-independent out-of-phase signals are observed. Above 8.1 K, temperature-dependent behavior is observed. Furthermore, we examined the AC magnetic susceptibility behavior under external magnetic fields ranging from 300 to 4000 G. The effect of QTM is significantly reduced in the presence of an external magnetic field. Temperature-dependent behavior is primarily governed by Raman relaxation. Through structural analysis of compound 1 and a series of pure nitrogen-coordinated single-ion magnets (SIMs), we propose that the oxo substituents from the double-deprotonated form of the 2,2'-bipyridine-6,6'-diol ligands donate their negative charge to the pyridine ring, forming amido anion sites. This triggers a more pronounced out-of-phase signal than that observed in pure pyridine-coordinated compounds. Moreover, we observed intermolecular interactions, including intermolecular hydrogen bonding, which, to some extent, influenced the slow relaxation of molecules. Therefore, we speculate that the slow relaxation phenomenon of compound 1 may be attributed to the combination of oxo back-donating effects and intermolecular interactions.
Competing Interests: The authors declare no competing financial interest.
(© 2024 The Authors. Published by American Chemical Society.) |
