Magnetic properties of 1:4 complexes of CoCl2 and pyridines carrying carbenes (S0 = 4/2, 6/2, and 8/2) in diluted frozen solution; Influence of carbene multiplicity on heterospin single-molecule magnets

Satoru Karasawa, Kimihiro Nakano, Jun Ichi Tanokashira, Noriko Yamamoto, Takahito Yoshizaki, Noboru Koga

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Abstract

The microcrystalline sample of a parent complex, [CoCl2(py) 4], showed a single-molecule magnet (SMM) behavior with an effective activation barrier, Ueff/kB, of 16 K for reversal of the magnetism in the presence of a dc field of 3 kOe. Pyridine ligands having 2-4 diazo moieties, DYpy; Y = 2, 3l, 3b, and 4, were prepared and confirmed to be quintet, septet, septet, and nonet in the ground state, respectively, after irradiation. The 1:4 complexes, CoCl2(DYpy)4; Y = 2, 3l, 3b, and 4 in frozen solutions after irradiation showed the magnetic behaviors of SMMs with total spin multiplicity, Stotal = 17/2, 25/2, 25/2, and 33/2, respectively. Hysteresis loops depending on the temperature were observed and the values of coercive force, Hc, at 1.9 K were 12, 8.4, 11, and 8.1 kOe for CoCl2(CYpy)4; Y = 2, 3l, 3b, and 4, respectively. In dynamic magnetic susceptibility experiments, ac magnetic susceptibility data obeyed the Arrhenius law to give Ueff/k B values of 94, 92, 93, and 87 K for CoCl2(CYpy) 4; Y = 2, 3l, 3b, and 4, respectively, while the relaxation times for CoCl2(CYpy)4; Y = 2 and 3l, obtained by dc magnetization decay in the range of 3.5-1.9 K slightly deviated downward from Arrhenius plots on cooling. The dynamic magnetic behaviors for CoCl2(CYpy) 4 including [CoCl2(py)4] and CoCl 2(C1py)4 suggested that the generated carbenes interacted with the cobalt ion to increase the relaxation time, τq, due to the spin quantum tunneling magnetization, which became larger with increasing Stotal of the complex.

Original languageEnglish
Pages (from-to)13656-13667
Number of pages12
JournalDalton Transactions
Volume41
Issue number44
DOIs
Publication statusPublished - Nov 28 2012

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Pyridines
Magnetic susceptibility
Relaxation time
Magnets
Magnetization
Magnetic properties
Irradiation
Arrhenius plots
Molecules
Magnetism
Hysteresis loops
Cobalt
Coercive force
Ground state
Chemical activation
Ions
Ligands
Cooling
Experiments
Temperature

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

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Magnetic properties of 1:4 complexes of CoCl2 and pyridines carrying carbenes (S0 = 4/2, 6/2, and 8/2) in diluted frozen solution; Influence of carbene multiplicity on heterospin single-molecule magnets. / Karasawa, Satoru; Nakano, Kimihiro; Tanokashira, Jun Ichi; Yamamoto, Noriko; Yoshizaki, Takahito; Koga, Noboru.

In: Dalton Transactions, Vol. 41, No. 44, 28.11.2012, p. 13656-13667.

Research output: Contribution to journalArticle

Karasawa, Satoru ; Nakano, Kimihiro ; Tanokashira, Jun Ichi ; Yamamoto, Noriko ; Yoshizaki, Takahito ; Koga, Noboru. / Magnetic properties of 1:4 complexes of CoCl2 and pyridines carrying carbenes (S0 = 4/2, 6/2, and 8/2) in diluted frozen solution; Influence of carbene multiplicity on heterospin single-molecule magnets. In: Dalton Transactions. 2012 ; Vol. 41, No. 44. pp. 13656-13667.
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abstract = "The microcrystalline sample of a parent complex, [CoCl2(py) 4], showed a single-molecule magnet (SMM) behavior with an effective activation barrier, Ueff/kB, of 16 K for reversal of the magnetism in the presence of a dc field of 3 kOe. Pyridine ligands having 2-4 diazo moieties, DYpy; Y = 2, 3l, 3b, and 4, were prepared and confirmed to be quintet, septet, septet, and nonet in the ground state, respectively, after irradiation. The 1:4 complexes, CoCl2(DYpy)4; Y = 2, 3l, 3b, and 4 in frozen solutions after irradiation showed the magnetic behaviors of SMMs with total spin multiplicity, Stotal = 17/2, 25/2, 25/2, and 33/2, respectively. Hysteresis loops depending on the temperature were observed and the values of coercive force, Hc, at 1.9 K were 12, 8.4, 11, and 8.1 kOe for CoCl2(CYpy)4; Y = 2, 3l, 3b, and 4, respectively. In dynamic magnetic susceptibility experiments, ac magnetic susceptibility data obeyed the Arrhenius law to give Ueff/k B values of 94, 92, 93, and 87 K for CoCl2(CYpy) 4; Y = 2, 3l, 3b, and 4, respectively, while the relaxation times for CoCl2(CYpy)4; Y = 2 and 3l, obtained by dc magnetization decay in the range of 3.5-1.9 K slightly deviated downward from Arrhenius plots on cooling. The dynamic magnetic behaviors for CoCl2(CYpy) 4 including [CoCl2(py)4] and CoCl 2(C1py)4 suggested that the generated carbenes interacted with the cobalt ion to increase the relaxation time, τq, due to the spin quantum tunneling magnetization, which became larger with increasing Stotal of the complex.",
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AU - Nakano, Kimihiro

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