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Enhancing the Blocking Temperature in Single-Molecule Magnets by Incorporating 3d-5d Exchange Interactions
- Source :
- Chemistry-A European Journal
- Publication Year :
- 2010
- Publisher :
- Wiley, 2010.
-
Abstract
- We report the first single-molecule magnet (SMM) to incorporate the [Os(CN)(6)](3-) moiety. The compound (1) has a trimeric, cyanide-bridged Mn(III)-Os(III)-Mn(III) skeleton in which Mn(III) designates a [Mn(5-Brsalen)(MeOH)](+) unit (5-Brsalen=N,N'-ethylenebis(5-bromosalicylideneiminato)). X-ray crystallographic experiments reveal that 1 is isostructural with the Mn(III)-Fe(III)-Mn(III) analogue (2). Both compounds exhibit a frequency-dependent out-of-phase χ''(T) alternating current (ac) susceptibility signal that is suggestive of SMM behaviour. From the Arrhenius expression, the effective barrier for 1 is found to be Δ(eff)/k(B)=19 K (τ(0)=5.0×10(-7) s; k(B)=Boltzmann constant), whereas only the onset (1.5 kHz, 1.8 K) of χ''(T) is observed for 2, thus indicating a higher blocking temperature for 1. The strong spin-orbit coupling present in Os(III) isolates the E'(1g(1/2))(O(h)*) Kramers doublet that exhibits orbital contributions to the single-ion anisotropy. Magnetic susceptibility and inelastic neutron-scattering measurements reveal that substitution of [Fe(CN)(6)](3-) by the [Os(CN)(6)](3-) anion results in larger ferromagnetic, anisotropic exchange interactions going from quasi-Ising exchange interactions in 2 to pure Ising exchange for 1 with J(parallel)(MnOs)=-30.6 cm(-1). The combination of diffuse magnetic orbitals and the Ising-type exchange interaction effectively contributes to a higher blocking temperature. This result is in accordance with theoretical predictions and paves the way for the design of a new generation of SMMs with enhanced SMM properties.
- Subjects :
- Arrhenius equation
010405 organic chemistry
Stereochemistry
Organic Chemistry
Exchange interaction
chemistry.chemical_element
General Chemistry
010402 general chemistry
01 natural sciences
Magnetic susceptibility
Catalysis
0104 chemical sciences
Ion
symbols.namesake
Crystallography
Ferromagnetism
chemistry
symbols
Molecule
Osmium
Isostructural
Subjects
Details
- ISSN :
- 09476539
- Volume :
- 16
- Database :
- OpenAIRE
- Journal :
- Chemistry - A European Journal
- Accession number :
- edsair.doi.dedup.....78dfafc860f6b33ee4939c64e07200f4