NH-bridged Dimeric Phosphazanes: Inorganic Molecular Switches based on Anion Responsive Bifurcated to Trifurcated Hydrogen Bond Transitions

Molecular machines and switches, supramolecular chemistry, and crystal engineering are vibrant areas of research. Organic chemists have devoted considerable efforts to develop a wide range of complex functional building blocks with enhanced properties and chemically responsive properties to advance these fields. However, the rational design of topologically versatile and chemically responsive building blocks in the main group arena is largely unexplored. Within this context, we have rationally designed a series of NH-bridged acyclic dimeric cyclodiphosphazanes species, [(μ-NH){PE(μ-NtBu)2PE(NHtBu)}2] (E= O and S), displaying bimodal bifurcated R21(8) and trifurcated R31(8,8) hydrogen bonding motifs. The reported species reversibly switch their topological arrangement in the presence 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.