Single molecule magnets with m-fluorobenzoate and difluoromethylacetate as polar ligands

Norihisa Hoshino, Takuya Shiga, Hiroki Oshio, Tomoyuki Akutagawa

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Two new single molecule magnets (SMMs), [Mn12O 12(CHF2COO)16(H2O) 4]·2CH2Cl2·4H2O (1) and [Mn12O12(m-FPhCOO)16(H2O) 4]·2(m-FPhCOOH)·7CH2Cl2 (2), based on a disc-shaped {Mn12O12}-framework with difluoromethylacetate (CHF2COO-) and m-fluorobenzoate (m-FPhCOO-) as polar ligands were prepared in CH2Cl 2. Structural analyses by X-ray diffraction at 100 K showed orientationally disordered fluorine atoms in the CHF2COO- and m-FPhCOO- ligands of crystals 1 and 2, respectively. In crystal 1, the fluorine atoms at the axial coordination sites of the disc-like {Mn 12O12}-framework exhibited large thermal parameters even at 100 K, suggesting that thermally activated rotation of the -CHF2 groups along the C-COO axis occurred in the CHF2COO- ligands. The SMMs behaviors of crystals 1 and 2 showed magnetization hysteresis at 1.8 K and frequency-dependent in-phase and out-of-phase ac magnetic susceptibilities, characteristic of SMMs. Frequency-dependent dielectric responses as well as two Debye-type relaxation processes at ∼100 and ∼220 K were observed in crystal 1, while such responses were not observed in crystal 2. The activation energy and blocking temperature of the relaxation process for 1 were 12 kJ mol-1 and 48 K, respectively, at ∼100 K, whereas those at ∼220 K were 66 kJ mol-1 and 153 K, respectively. In 1, the two polarization types at ∼100 and ∼220 K were associated with thermally activated fluctuations of the hydrogen-bonded crystalline H2O molecules and rotation of the -CHF2 group in the CHF2COO- ligand.

Original languageEnglish
Pages (from-to)4377-4385
Number of pages9
JournalDalton Transactions
Volume42
Issue number13
DOIs
Publication statusPublished - 2013 Apr 7

ASJC Scopus subject areas

  • Inorganic Chemistry

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