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

Abstract

Two new single molecule magnets (SMMs), [Mn(12)O(12)(CHF(2)COO)(16)(H(2)O)(4)]·2CH(2)Cl(2)·4H(2)O (1) and [Mn(12)O(12)(m-FPhCOO)(16)(H(2)O)(4)]·2(m-FPhCOOH)·7CH(2)Cl(2) (2), based on a disc-shaped {Mn(12)O(12)}-framework with difluoromethylacetate (CHF(2)COO(-)) and m-fluorobenzoate (m-FPhCOO(-)) as polar ligands were prepared in CH(2)Cl(2). Structural analyses by X-ray diffraction at 100 K showed orientationally disordered fluorine atoms in the CHF(2)COO(-) 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(12)O(12)}-framework exhibited large thermal parameters even at 100 K, suggesting that thermally activated rotation of the -CHF(2) groups along the C-COO axis occurred in the CHF(2)COO(-) 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 H(2)O molecules and rotation of the -CHF(2) group in the CHF(2)COO(-) ligand.

Ionic Conductivities Induced by the Partial Solvent Molecule Removal from Diruthenium(II,III) Adamantanecarboxylate Salts

“…Linear alkyl chains and globular substituents also exhibit uniaxial rotations in crystals 9,10 and often affect the physical properties of the solids, such as thermal conductivities, 11 birefringences, 12,13 chirality, 14 and dielectricities. 15,16 In this work, we prepared dinuclear Ru(II,III) paddlewheels bearing substituted adamantyl groups as molecular rotators (Figure 1). They have been reported as useful functional building blocks with electron acceptability and magnetic anisotropy, and various functional metal−organic frameworks have been reported from their combinations with the bridging ligands coordinating to the axial sites of the Ru(II,III ions.…”

“…In the crystal, as the molecules are orientationally disordered, the crystal defects and diffusions increase, and it becomes plastic. Linear alkyl chains and globular substituents also exhibit uniaxial rotations in crystals , and often affect the physical properties of the solids, such as thermal conductivities, birefringences, , chirality, and dielectricities. , In this work, we prepared dinuclear Ru­(II,III) paddlewheels bearing substituted adamantyl groups as molecular rotators (Figure ). They have been reported as useful functional building blocks with electron acceptability and magnetic anisotropy, and various functional metal–organic frameworks have been reported from their combinations with the bridging ligands coordinating to the axial sites of the Ru­(II,III) 2 ions. − However, we found that the crystals of the discrete paddlewheels 1 – 3 also exhibit ionic conductivity along with the partial removal of the crystal solvent molecules.…”