A Flexible Coordination Polymer Crystal Providing Reversible Structural and Magnetic Conversions

Structural flexibility is a remarkable characteristic of coordination polymers and significant for
the attainment of environmental responsivity. We have prepared a 2D cyanide-bridged MnIICrIII coordination
polymer, [Mn(NNdmenH)(H2O)][Cr(CN)6]·H2O (1; NNdmen = N,N-dimethylethylenediamine), with sophisticatedly arranged removable water coligands. The compound clearly showed a reversible single-crystal-to-single-crystal transformation between the 2D sheet and a 3D pillared-sheet framework of dehydrated
[Mn(NNdmenH)][Cr(CN)6] (1a). The structural change was reversible and accompanied with generation/cleavage of CN−Mn bonds between 2D sheets by dehydration/hydration. Compounds 1 and 1a also
exhibited a ferrimagnetic ordering at 35.2 and 60.4 K, respectively, and the magnetic characteristics were
reversibly converted by guest adsorption/desorption. In addition, the dehydrated 1a demonstrated a size-selective solvent adsorption linking chemi- and physisorption processes and shrinkage/expansion of its
framework. The flexible magnetic framework incorporating removable coligands delivered multifunctions
with chemical response.