Double spin transition in a two dimensional Fe(ii) coordination network.

In the two dimensional network [Fe(ebbtr)2(CH3CN)2](ClO4)2·4CH3CN a sequence of LS → HS → LS → HS transitions occurs as the exclusive result of the change in temperature. This property results from the extraordinary flexibility/elasticity manifested in the hierarchical arrangement of structural events involving the reorientation of coordinated/noncoordinated molecules as well as with the deformation and the mutual shift of the polymeric units.