Nature of the magnetic interaction of Wurster's radicals in the solid state

Nature of the Magnetic Interaction in Organic Radical Crystals. 3. Galvinoxyl Radicals in 1-D Crystals,

“…∆ depends on the topology and the geometry of the stacks: ∆ is zero (or has small values) in the case of models of class (i); ∆ has finite values which increase with increasing slip angle R. Quantitatively, the same conclusion was drawn from theoretical investigations of the nature of the magnetic interaction of Wurster's radicals in the solid state. 16 The intermolecular magnetic coupling within the MRCs is 1 order of magnitude smaller in comparison with the intramo-lecular magnetic coupling between galvinoxyl radicals connected by meta-phenylene units in an 1-D polymer.…”

“…In contrast to galvinoxyl MRCs, the magnitude of the magnetic interaction (antiferromagnetic in nature) between neighboring Wurster's radicals in the 1-D stacks of Wurster's Red Bromide is large, J eff ∼ 0.1 eV. 16 This relative large absolute value of J eff is caused by the short interplanar distance between the Wurster's radicals in the stacks (R(exp) ) 3.105 Å 22 ).…”

“…Parametrization. A standard value β 0 ) -2.4 eV 15,16,26 has been used for the resonance integral between 2pπ-2pπ AOs of the carbon atoms at a distance R 0 ) 1.40 Å. β(C-O) ) -2.4 eV. The parameter used for the Coulomb integral of oxygen is R O ) R C -1.5β 0 .…”

“…In the first communications of this series 15,16 we have begun to study the correlation between the composition, topology, and geometry of MRCs and the nature of the exchange interaction using the band model. It was applied to 1-D crystals in which the EUs are radicals with delocalized π-electron systems.…”

Design of ferromagnetic alternating stacks of neutral and ion-radical hydrocarbons

“…Thus homo-radical stacks (Scheme 1a) are likely to exhibit anti-parallel spin alignment and zero net collective spin, as shown for neutral and charged Wurster-type radicals. 14,15 If a diamagnetic molecule (N) is inserted between each pair of radicals in the stack, its spin polarisation (SP), albeit weak, can lead to an effective ferrimagnetic ordering with the large spin-up/down densities on the radicals and small (induced) spin-down/-up density on the spacers (Scheme 1b).…”