High pressure and very low temperature effects on the crystal structures of some iron(II) complexes

The crystal structures at 30 K of two iron(II) complexes, and their compari son with higher temperature crystal structures indicate that outside of the spin transition range, the only intramolecular modification comes from dyn amical aspects. The contraction of the packing is strong from 110 to 30 K a nd similar in both complexes. The high pressure (0.16 GPa. 0.40 GPa) crysta l structures of another iron(II) complex of the same family show that stron g changes are induced cinder pressure within the packing but that to a firs t approximation, the effects of temperature (11 K) or pressure (0.40 GPa) o n the intermolecular contacts are very similar even though one S...C interm olecular contact is significantly different. Moreover, slight differences i n the cell parameter changes are noted. We also show that the deformation o f thr iron(II) coordination sphere does not depend on the applied constrain t but on the spin state only. (C) Academie des sciences , Editions scientif iques et medicales Elsevier SAS.