Actas de congresos
Structural Studies Of Iron (Iii) Complexes Containing Schiff Base N4o2 Ligands
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).
REFERENCES
[1] Tissot, R Bertoni, E2. Collet, L. Toupet, M-L Boillot, (2011) J. Mater. Chem. , 21, 18347-18353.
[2] M. A. Spackman, D. Jayatilaka, (2009) CrystEngcomm 11, 19.