3 research outputs found
Synthesis, Structure, and Magnetic Properties of 1D {[Mn<sup>III</sup>(CN)<sub>6</sub>][Mn<sup>II</sup>(dapsc)]}<sub><i>n</i></sub> Coordination Polymers: Origin of Unconventional Single-Chain Magnet Behavior
Two one-dimensional
cyano-bridged coordination polymers, namely,
{[Mn<sup>II</sup>(dapsc)]Â[Mn<sup>III</sup>(CN)<sub>6</sub>]Â[KÂ(H<sub>2</sub>O)<sub>2.75</sub>(MeOH)<sub>0.5</sub>]}<sub><i>n</i></sub>·0.5<i>n</i>(H<sub>2</sub>O) (<b>I</b>) and {[Mn<sup>II</sup>(dapsc)]Â[Mn<sup>III</sup>(CN)<sub>6</sub>]Â[KÂ(H<sub>2</sub>O)<sub>2</sub>(MeOH)<sub>2</sub>]}<sub><i>n</i></sub> (<b>II</b>), based on alternating high-spin
Mn<sup>II</sup>(dapsc) (dapsc = 2,6-diacetylpyridine bisÂ(semicarbazone))
complexes and low-spin orbitally degenerate hexacyanomanganateÂ(III)
complexes were synthesized and characterized structurally and magnetically.
Static and dynamic magnetic measurements reveal a single-chain magnet
(SCM) behavior of <b>I</b> with an energy barrier of <i>U</i><sub>eff</sub> ≈ 40 K. Magnetic properties of <b>I</b> are analyzed in detail in terms of a microscopic theory.
It is shown that compound <b>I</b> refers to a peculiar case
of SCM that does not fall into the usual Ising and Heisenberg limits
due to unconventional character of the Mn<sup>III</sup>–CN–Mn<sup>II</sup> spin coupling resulting from a nonmagnetic singlet ground
state of orbitally degenerate complexes [Mn<sup>III</sup>(CN)<sub>6</sub>]<sup>3–</sup>. The prospects of [Mn<sup>III</sup>(CN)<sub>6</sub>]<sup>3–</sup> complex as magnetically anisotropic
molecular building block for engineering molecular magnets are critically
analyzed
Multifunctional Compound Combining Conductivity and Single-Molecule Magnetism in the Same Temperature Range
We report the first
highly conducting single-molecule magnet, (BEDO)<sub>4</sub>[ReF<sub>6</sub>]·6H<sub>2</sub>O [<b>1</b>; BEDO = bisÂ(ethylenedioxo)Âtetrathiafulvalene],
whose conductivity and single-molecule magnetism coexist in the same
temperature range. The compound was synthesized by BEDO electrocrystallization
in the presence of (Ph<sub>4</sub>P)<sub>2</sub>[ReF<sub>6</sub>]·2H<sub>2</sub>O and characterized by crystallography and measurements of
the conductivity and alternating-current magnetic susceptibility
The Conducting Spin-Crossover Compound Combining Fe(II) Cation Complex with TCNQ in a Fractional Reduction State
The radical anion
salt [FeÂ{HCÂ(pz)<sub>3</sub>}<sub>2</sub>]Â(TCNQ)<sub>3</sub> demonstrates
conductivity and spin-crossover (SCO) transition associated with FeÂ(II)
complex cation subsystem. It was synthesized and structurally characterized
at temperatures 100, 300, 400, and 450 K. The compound demonstrates
unusual for 7,7,8,8,-tetracyanoquinodimethane (TCNQ)-based salts quasi-two-dimensional
conductivity. Pronounced changes of the in-plane direct-current resistivity
and intensity of the electron paramagnetic resonance (EPR) signal,
originated from TCNQ subsystem, precede the SCO transition at the
midpoint <i>T</i>* = 445 K. The boltzmannian growth of the
total magnetic response and structural changes in the vicinity of <i>T</i>* uniquely show that half [FeÂ{HCÂ(pz)<sub>3</sub>}<sub>2</sub>] cations exist in high-spin state. Robust broadening of the EPR
signal triggered by the SCO transition is interpreted in terms of
cross relaxation between the TCNQ and FeÂ(II) spin subsystems