Functional (Supra)Molecular Nanostructures - ruben-group

Habilitation Dr. Mario Ruben
ULP Strasbourg
state in order to reveal the influence of the nature of ligand L on the magnetic behavior of the
complexes.
Figure 17. Schematic representation of the two series of [2x2] Fe II 4L 1 4 complexes 5-9
varying substituent R 1 and 10-12 varying substituent R 2 of L 1 .
In a first series of compounds (compounds 5-9 [Fe4 II L 1 4](X)8), the coordination
sphere of the [2x2] grid-type complexes was varied by changing the substituent R 1 in the 2-
position of the pyrimidine of the incorporated ligands L 1 (L = C-G with R 1 = H, OH, Me, Ph,
p-PhNMe2). In a second series of compounds (compounds 10-12 [Fe4 II L 1 4](X)8), the ligands
were additionally altered at the periphery. Thus, in complexes 10 and 11 S- n propyl groups
were introduced in the 4`-position of the ligands (complex 10 [Fe4 II H4](PF6)8 and complex 11
[Fe4 II I4](ClO4)8). In complex 12, [Fe4 II J4](BF4)8, the peripheral pyridyl ring of the ligand
backbone was exchanged by a 5´´-aminopyrazin-2´´yl group yielding ligand J (Figure 17).
The investigations have shown that the occurrence of spin transition in [2x2] grid-
like complexes of the type [Fe II 4L 1 4](X)8 depends directly on the nature of the substituent R 1
in the 2-position of the ligand L 1 . All compounds with substituents in this position favoring
strong ligand fields (R 1 = H; OH) remain completely in the LS state at all temperatures
studied. Only complexes bearing substituents which attenuate the ligand field by steric (and to
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