Stabilization of 2D water sheets in a supramolecular metal–organic Schiff base complex: Reversible structural transformation upon dehydration–rehydration

A new metal–organic complex {[Ni(HL1)Cl]2·5H2O} has been synthesized using a Schiff base ligand H2L1 [where H2L1 = N,N′-(2-hydroxy)propylenebis(2-imino-3-oximino)butane] and characterized by single crystal X-ray crystallographic, IR and thermal studies. Structural analysis reveals that the complex crystallizes in achiral C2/c space group and it has 3D supramolecular structure. Hydrogen bonding interactions among the metal–organic moieties form 2D supramolecular sheets within the crystallographic ab-plane. These 2D sheets are packed along crystallographic c-axis with formation of 1D supramolecular channels along crystallographic a-axis and thus the complex behaves like metal–organic supramolecular host (MOSH). Five guest water molecules get stability within the supramolecular channels through hydrogen bonding interactions. Hydrogen bonding interactions among the guest water molecules produce 2D supramolecular sheets within the ab-plane with (H2O)12 morphology. These supramolecular water sheets are of two different types: one contains only right handed helical chains and the other contains only left handed helical chains. The complex undergoes reversible structural transformation upon dehydration–rehydration.

A metal organic supramolecular host (MOSH) based on metal–organic complex {[Ni(HL1)Cl]2·5H2O} [where H2L1 = N,N′-(2-hydroxy)propylenebis(2-imino-3-oximino)butane] gives stability to a 2D water layer through hydrogen bonding interactions. Water molecules also form both right and left handed supramolecular helical chains by hydrogen bonding interactions. The complex undergoes reversible structural transformation upon desorption and adsorption of guest water molecules.Figure optionsDownload as PowerPoint slideHighlights
► Metal–organic supramolecular host.
► Water pentamer.
► 2D supramolecular sheet of water.
► Supramolecular helical chain.
► Reversible structural transformation.