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Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate
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Slow magnetic relaxation in five-coordinate spin-crossover cobalt(ii) complexes
Hui-Hui Cui1, Jing Wang, Xue-Tai Chen
1State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. xtchen@nju.edu.cn.
Chemical Communications (Cambridge, England)
|July 25, 2017
Summary
This study reveals the first instances of slow magnetic relaxation and spin-crossover occurring together in cobalt(II) complexes. These findings in five-coordinate cobalt(II) complexes provide new insights into magnetic phenomena.
Area of Science:
- Coordination Chemistry
- Magnetochemistry
- Materials Science
Background:
- Spin-crossover (SCO) is a phenomenon where transition metal complexes can switch between low-spin and high-spin states.
- Slow magnetic relaxation is crucial for developing molecular magnetic materials and memory devices.
Purpose of the Study:
- To investigate the coexistence of field-induced slow magnetic relaxation and spin-crossover in novel five-coordinate cobalt(II) complexes.
- To characterize the magnetic properties of these complexes under varying conditions.
Main Methods:
- Synthesis of five-coordinate cobalt(II) complexes: [Co(12-TMC)(CH3CN)](X)2, where 12-TMC is 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane and X = BF4- or PF6-.
- Direct-current (dc) magnetic susceptibility measurements to analyze spin-crossover behavior.
- Alternating-current (ac) magnetic susceptibility measurements under an applied dc field to study slow magnetic relaxation.
Main Results:
- The synthesized cobalt(II) complexes exhibit gradual and incomplete spin-crossover at higher temperatures.
- Frequency- and temperature-dependent ac magnetic susceptibility was observed under a 2500 Oe dc field, indicating slow magnetic relaxation.
- The observed magnetic relaxation originates from the S = 1/2 spin state of the cobalt(II) ions.
Conclusions:
- The study successfully demonstrates the simultaneous occurrence of slow magnetic relaxation and spin-crossover in the investigated cobalt(II) complexes.
- These findings represent the first examples of such a dual magnetic behavior in five-coordinate cobalt(II) systems.
- The results contribute to the understanding of complex magnetic phenomena in coordination compounds and their potential applications.
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