[Zurück]

I. Nemec, R. Herchel, Z. Trávníček, I. Svoboda, W. Linert:
"Spin transition in iron(III) complexes with pseudohalide terminal ligands";
Poster: 26th European Crystallographic Meeting, Damstadt; 29.08.2010 - 02.09.2010; in: "26th European Crystallographic Meeting, ECM 26, Darmstadt, 2010", Acta Cryst., A66 (2010), ISSN: 0108-7673; S. 255.

Spin transition (ST) is well documented for coordination compounds of the first transition row with d4-d7 configuration of valence shell [1] and it is observed in most cases for iron(II) and iron(III) complexes . Recently, we have reported about magnetic properties of the dinuclear cyanido-bridged Fe(III) complexes where ST is heavily influenced by strong antiferromagnetic exchange interaction through the cyanido linkage [2]. Despite the present cooperative interactions, spin-transition is of a very gradual character. In order to remove the strong exchange coupling, the dinuclear compounds were transformed into mononuclear ones by substitution of a cyanido linkage with appropriate terminal ligand, which would maintain presence of ST. We decided to use pentadentate Schiff base ligands L5 with {N3O2} donor set and as a substitution to a cyanido ligand the pseudohalide ligands were chosen. This also offers possibility to carry out very fine tuning of the overall ligand field by single substitution with respect to known spectrochemical row of ligands. The X-ray analysis and magnetic measurements confirmed the spin transition in some of the prepared compounds and ST is only secondarily influenced by clathrated solvent molecules. Different solvent molecules lead to different packing motives and those lead to different geometries of L5. The molecules which do not undergo ST have different dihedral angle between the least square planes of aromatic rings of L5 ligand from those that exhibit ST. This was also observed for compounds of iron(III) with hexadentate Schiff based ligands [3]. The compounds which show ST were structurally characterized at different temperatures and temperature dependence of their lattice parameters was done.