Actas de congresos
Structural Studies of Iron(III) Complexes with N4O2 Coordination Sphere
Fecha
2014Institución
Resumen
The Spin-Crossover (SCO) phenomenon implicates a switchable between a low-spin (LS) diamagnetic state, which is stable at low
temperatures and a paramagnetic high-spin state (HS), which is stable at higher temperatures. This transition is generated by an
external perturbation such as temperature, pressure or light. In general, the switching process in solid-state systems is controlled by
cooperative intermolecular interactions. The correlation of structure with physical properties is crucial to the identification of these
interactions and ultimately the understanding of the complex processes that control the SCO phenomenon[1]. With the aim of
developing new SCO materials, we carried out the syntheses and crystal structure analysis of seven iron(III) complexes, mixing 5-
bromo-salicylaldehyde or 5-chloro-salicylaldehyde and ethylendiamine with iron(III) chloride and/or ammonium hexafluorophosphate
solutions by slow diffusion or reflux in methanol or 2-propanol (figure 1). The crystal structures show the iron(III) centre is
hexacoordinated (FeN4O2) and the coordination polyhedron can be described as a distorted octahedron formed by the 4 N
atoms of the ethylenediamine fragment and 2 hydroxyl O atoms from the salicylaldehyde fragment, this distortion was evaluated at
120 and 298 K, the major distortion were observed in complexes [2]+ PF6–· MeOH, [2]+ PF6–·iPrOH and [1]+ PF6–·MeOH, which is
characteristic in HS states, while the complexes [2]+ Cl–·iPrOH, [1]+ PF6–·iPrOH [2]+ and [2]+ClO4–, shows a minor distortion
according to LS states. On the other hand, [1]+ClO4– is a SCO complex with a typical geometry for both spin states at 120 K (LS) and
298 K (HS). Finally, we studied the intermolecular interactions using Crystal Explorer Software[2] between the iron complexes, the
counterion and/or the solvate molecule, for instance, in the [2]+PF6–·MeOH complex, the most remarkable feature observed are
Br···Br intermolecular interactions (figure 2).