Main Group Molecular Switches with Swivel Bifurcated to Trifurcated Hydrogen Bond Mode of Action

Artificial molecular machines have captured the full attention of the scientific community since Jean-Pierre Sauvage, Fraser Stoddart, and Ben Feringa were awarded the 2016 Nobel Prize in Chemistry. The past and current developments in molecular machinery (rotaxanes, rotors, and switches) primarily rely on organic-based compounds as molecular building blocks for their assembly and future development. In contrast, the main group chemical space has not been traditionally part of the molecular machine domain. The oxidation states and valency ranges within the p-block provide a tremendous wealth of structures with various chemical properties. Such chemical diversity-when implemented in molecular machines-could become a transformative force in the field. Within this context, we have rationally designed a series of NH-bridged acyclic dimeric cyclodiphosphazane species, [(mu-NH){PE(mu-(NBu)-Bu-t)(2)PE((NHBu)-Bu-t)}(2)] (E = O and S), bis-(P2N2)-N-V, displaying bimodal bifurcated R-1(2)(8) and trifurcated R-1(3)(8,8) hydrogen bonding motifs. The reported species reversibly switch their topological arrangement in the presence and absence of anions. Our results underscore these species as versatile building blocks for molecular machines and switches, as well as supramolecular chemistry and crystal engineering based on cyclophosphazane frameworks.

Automated summary

Artificial molecular machines, primarily using organic compounds, have received significant attention in the scientific community. However, the main group chemical space has been less explored in this field. This study introduces NH-bridged acyclic dimeric cyclodiphosphazane species as versatile building blocks for molecular machines and switches, opening up new possibilities for supramolecular chemistry and crystal engineering.