Iron(ii) pillared-layer responsive frameworks via “kagomé dual” (kgd) supramolecular tessellations

Abstract

Supramolecular tessellation represents a newly emerging powerful tool for constructing crystalline and quasicrystalline structural aesthetics with molecular polygons/planigons. In turn, expanding such 2-periodic tessellation as tectonic layer to 3-periodic architecture of frameworks, promises the sublimation from visual beauty for pure appreciation to sophisticated performance of porous materials for real application, enabling us to build macroscopic behavior at the molecular scale. With the above foresight, we introduce herein a new discovery that integrating supramolecular tessellation and pillared-layer strategy assembles supramolecular frameworks (SFs). The tectonic layers are based on rhombille tessellation of hydrogen-bondings between Fe^II molecular building blocks and interstitial water molecules, showing a rare kagomé dual (kgd) net. Under this strategy, we first observed that a new zlg 3D topology was born by pillaring with kgd layer. These SFs offer potential channel/voids for guests’ respiration, inducing a reversible allosteric transformation from ligand substitution. The transformation alters significantly the spin state which was quantified by ⁵⁷Fe Mössbauer spectroscopy, NMR, magnetic dilution and DFT calculations. These compounds show magnetic and chromatic bistability (see TOC), providing a broad scope towards multifuctional frameworks via multifarious supramolecular tessellation.