From 2D to 3D solids: stacking of transition metal nitroprusside layers through intermolecular physical interactions

This contribution reports the preparation and study of a series of hybrid inorganic-organic solids obtained by intercalation of pyridine molecules between neighboring layers of 2D transition metal nitroprussides, T[Fe(CN)₅NO]. The pyridine molecule coordinated to the axial positions for the metal (T) linked at the N ends of the equatorial CN ligands. From such regular pyridine molecule disposition at the layer and the attractive dispersive interactions and dipole-dipole coupling between neighboring molecules in the interlayer region, the formation of a long range 3D framework results. The refined crystal structure and the magnetic measurements shed light on the interaction between intercalated neighboring molecules. In the resulting 3D framework, the hybrid material preserves its 2D identity because no formation of chemical bonds is involved in the stacking process. Such structural features are properly supported by the refined crystal structures and computational studies for the interaction of the organic molecule with the metal (T) center. This series of hybrid solids crystallizes with an orthorhombic unit cell in the Ic2m space group. The unit cell volume shows a slight dependence of the metal (T), Ni < Co < Zn < Mn, which is related to the metal polarizing power and follows the order found for the T-N_CN and T-N_Py bond distances. The results herein discussed are relevant for hybrid inorganic-organic materials design, preparation and applications.