Peripherally multi-functionalised metallosupramolecular grids: assembly, decoration, building blocks for dynamic covalent architectures

Abstract

The sequential assembly of first terminally functionalized bishydrazone ligands followed by their coordination with Zn(II) metal cations yields peripherally multi-functionalized [2 × 2] grid-type complexes. In particular, the introduction of aldehyde functional groups results in the generation of octavalent grids bearing eight reactive aldehyde units positioned in-plane on its outer rim. Their successful condensation with various amines and hydrazines introduces reversibly connected imine/hydrazone side chains. It points to their potential as a metallosupramolecular platform for executing diverse “second-shell” dynamic covalent decorations and for their implementation as building block for dynamic architectures. Thus, connection of two of the bishydrazone ligands in the grid complex with a difunctional covalent linker led to the formation of folded molecular grids of “double hairpins” geometry. These double hairpins grid architectures present two faces accessible for functionalization and two orthogonal ones that are blocked by the bent linker. This directionality was exploited in the second generation of folded grids/double hairpins, which were purposely decorated with aldehyde groups in order to perform multi-functional dynamic covalent chemistry and give access to novel complex architectures such as “grid of grids” arrays. The promising conjunction of a spatial organization of grids together with the endless diversity of imine dynamic chemistry provides an appealing basis for further development along various fields of interest (e.g.: multivalency, dynamic assembly of grids arrays, multifunctional decoration, etc.).