NoteSynthesis and characterization of Fe(III)(3-CH3O-qsal)2PF6 · nH2O (n = 0, 2)
Graphical abstract
Compounds FeIII(3-CH3O-qsal)2PF6 · nH2O (n = 0, 2) were synthesized and characterized. The hydrated one present properties characteristic of high-spin Fe(III), while the dry one of low-spin Fe(III). The dry compound has a beginning of spin crossover at high temperatures.
Introduction
Some transition metal complexes, e.g. some of iron (III), present a spin crossover (SCO) phenomenon induced by the application of an external stimulus such as temperature, pressure or light. This transition is indicated by a magnetic and structural change, and depends strongly on the cooperativity between building blocks [1]: the phenomenon may be tuned through changes in, e.g. ligand, counter-ion or even the presence of solvates. The coordination environment FeN4O2 is able to produce several complexes with SCO properties [1]. An example is [FeIII(qsal)2]+ (Hqsal = N-(8-quinolyl)salicylaldimine) (see e.g. Refs. [2], [3]). Several other Fe(III) complexes with a N2O-donor set are also able to exhibit SCO properties, however, as far as we know, regarding the qsal, only the unsubstituted one and the derivated qnal (Hqnal = N-(8-quinolyl)-2-hydroxy-1-naphthaldimine) were reported [1], [4]. Recently we have started to use ligands derived from qsal in order to obtain new SCO Fe(III) complexes. The chosen substituents are expected to lead to an increase of the interaction between the Fe(III) complexes and, in this way, to the enhancement of the cooperativity of the SCO transitions. This is included in a much broader effort that is taking place: the search of multifunctionality, either through the introduction of the appropriate counter-ion or through the modification of the ligands. In the present paper we report the introduction of a CH3O-group in the qsal ligand (see Scheme 1), where this electron donor group is expected to favor the stabilization of the high-spin (HS) configuration relative to the complex with the unsubstituted ligand. This group is also expected to lead to the increase of the interactions between the Fe(III) complexes through H-bonding.
Section snippets
General procedures
Commercial solvents were used without further purification unless otherwise specified. Although the synthesis of FeIII(3-CH3O-qsal)2Cl · H2O and of 3-CH3O-qsal ligand were not previously described they were prepared according to an adapted literature procedure [2]. The purity of the complexes was verified determining the carbon, hydrogen and nitrogen content by the ITN Elemental Analysis Service. X-ray diffraction experiments were performed with a Bruker AXS APEX CCD detector diffractometer using
Results and discussion
Fig. 1 shows the standard ORTEP [10] with 40% thermal ellipsoids and atom numbering scheme cation residue of compound 1, the crystallographic parameters are presented in Table 1 and selected bond lengths and angles in Table 2. The compound crystallizes in the triclinic space, space group . The asymmetric unit contains one cationic unit lying on a general position and two halves of anionic units with the P atom lying on centers of symmetry. The coordination bond lengths around the Fe(III) ion
Acknowledgements
This work was partially supported by Fundação para a Ciência e Tecnologia (Portugal) under contract PTDC/QUI/65379/2006 and grant SFRH/BPD/21873/2005. This work also benefited from MAGMANet network of excellence.
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