Linking the ends of ligands in interwoven grids could prove useful for tuning systems that display spin-crossover behavior.
These results suggest that interwoven grids could form the basis of a general strategy for the rational synthesis of higher-order knots and links.
Interwoven grids are much rarer, 12 but the crossing of the ligand strands in such systems make them, in principle, suitable scaffolds for constructing various interlocked structures.
In the search for a new interwoven-grid-forming ligand, we identified 1 as a potential candidate (Scheme 1).
4e Connecting the adjacent termini of parallel ligand strands in an interwoven 2×2 grid should afford a Solomon link.
The diastereotopic splitting of protons H i confirmed that the two faces of each ligand were in different environments, an inherent property of an interwoven 2×2 grid.
The eight aromatic rings of each ligand strand are rendered virtually co-planar by coordination to octahedral zinc II) cations in the interwoven 2×2 grid motif.
A molecular Solomon link was synthesized through the assembly of an interwoven molecular grid consisting of four bis(benzimidazolepyridyl benzthiazolo[5,4-d]thiazole ligands and four zinc(II), iron(II), or cobenzimidazolepyridyl benzthiazolo[5,4-d]thiazolen metathesis.
The synthesis, in which each metal ion defines the crossing point of two ligand strands, suggests that interwoven molecular grids should be useful scaffolds for the rational construction of other topologically complex structures.
In our efforts to produce such a system, we initially investigated functionalized analogues of ligands previously shown to form interwoven 2×2 grids, but the derivatives we prepared had poor solubility profiles as either the free ligand or as metal complexes.
Here we report on the designed synthesis of a Solomon link utilizing an interwoven 2×2 molecular grid to create a crossing point at the site of each metal ion.
