Magnetic properties after irradiation of 1:4 complexes consisting of cox2, X = NCS-, Cl-, and NCO-, and phenylpyridyldiazomethane in dilute frozen solutions: Axial ligand effect in heterospin single-molecule magnets

Satoru Karasawa, Noboru Koga

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Abstract

The solutions of 1:4 complexes of Co(X)2- (D1py)4, X = Cl-, and NCO- and D1py = phenylpyridyldiazomethane, were photolyzed under cryogenic conditions, and their magnetic properties were investigated by direct current (DC) and alternating current (AC) magneto/susceptometries. After irradiation, the resulting cobalt-carbene complexes, Co- (X)2(C1py)4, exhibited the behaviors of heterospin singlemolecule magnets (SMMs) strongly depending on the axial ligands. In Co(X)2(C1py)4: X = Cl- and NCO -, the effective activation barriers, Ueff, for the reorientation of the magnetic moment and the resonant quantum tunneling time, τQ, characteristic to SMM properties were estimated to be 91 and 130 K, and 4 × 103 and 2 × 105 s, respectively. The τQ of Co(NCS)2(C1py)4 with U eff = 89 K was found to be 6 × 102 s. In Co(X) 2(C1py)4: X=Cl- and NCO-, temperature-dependent hysteresis loops were also observed below the blocking temperature (TB = 3.2 and 4.8 K, respectively) and the coercive forces, Hc, of 7.0 and 20 kOe at 1.9 K, respectively, were obtained. In a series of 1:4 complexes of Co(X)2(C1py)4, X = NCS-, Cl-, andNCO-, the axial ligands strongly affected the heterospinSMMproperties, and theNCO- ion having the large magnitude of the ligand-field splitting in a spectrochemical series, gave the largest Ueff and Hc and the longest τQ.

Original languageEnglish
Pages (from-to)5186-5195
Number of pages10
JournalInorganic Chemistry
Volume50
Issue number11
DOIs
Publication statusPublished - Jun 6 2011

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All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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