9 research outputs found
Helical Folding-Induced Stabilization of Ferromagnetic Polyradicals Based on Triarylmethyl Radical Derivatives
Magnetic ordering
in purely organic Ļ-conjugated materials is a challenging, rare,
and desirable event. The interest lies on the unique magnetic properties
derived from high-spin carbon-based polymers/macromolecules tailored
through appropriate synthetic routes. Ground-breaking achievements
have been reported regarding magnetic ordering in an organic polymer
using spin clusters as building blocks. This strategy leads to two-dimensional
extended polyradicals with a concomitant loss of appealing macroscopic
properties such as expected magnetic anisotropy in elongated shaped
macromolecules containing carbon-bearing radicals. Here we provide
compelling evidence of a secondary structure-induced stabilization
of ferromagnetic polyradicals with robust magnetic properties and
strongly suggest revisiting a discarded attempt to obtain polymeric
linear-like radicals. An alternative synthetic approach is also proposed,
based on polyradicals obtained from discrete molecular precursors
(oligomers) long enough to ensure a secondary structure, rather than
from polymerization processes
Spin adapted versus broken symmetry approaches in the description of magnetic coupling in heterodinuclear complexes
The performance of a series of wave function and density functional theory based methods in predicting the magnetic coupling constant of a family of heterodinuclear magnetic complexes has been studied. For the former, the accuracy is similar to other simple cases involving homodinuclear complexes, the main limitation being a sufficient inclusion of dynamical correlation effects. Nevertheless, these series of calculations provide an appropriate benchmark for density functional theory based methods. Here, the usual broken symmetry approach provides a convenient framework to predict the magnetic coupling constants but requires deriving the appropriate mapping. At variance with simple dinuclear complexes, spin projection based techniques cannot recover the corresponding (approximate) spin adapted solution. Present results also show that current implementation of spin flip techniques leads to unphysical results.close2