Secondary hierarchical complexity in double-stranded cluster helicates covered by NNNNN type pincer ligands

We designed and synthesized a new tripyridine dipyrrolide pincer ligand, which could be doubly deprotonated to provide five-nitrogen-donor sites and then utilized to prepare a subnanometric chiral silver cluster. The cluster belongs to an S-4 point group and shows a double-stranded helicate. DFT calculations were performed to analyze the electronic structure of the cluster. Interestingly, through hierarchical intercluster interactions, the cluster helicates evolve into complex secondary structures including a right-handed helix and a folded sheet, both of which are reminiscent of secondary structures of proteins, i.e., an alpha-helix and an antiparallel beta-sheet.

Automated summary

We synthesized a new tripyridine dipyrrolide pincer ligand and used it to prepare a subnanometric chiral silver cluster. The cluster exhibited a double-stranded helicate structure. Interestingly, through hierarchical intercluster interactions, the cluster helicates evolved into complex secondary structures resembling protein secondary structures.