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

Abstract

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, [(μ-NH){PE(μ-NtBu)2PE(NHtBu)}2] (E = O and S), bis-PV 2N2, displaying bimodal bifurcated R2 1(8) and trifurcated R3 1(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.

Ligand-enforced geometric constraints and associated reactivity in p-block compounds

“…239,240 In the context of growing the multidentate frameworks used, chemists may find motivation from the field of ion sensing, where cooperative binding by construction of rigid hemispheric or macrocyclic molecules is a well-established strategy for boosting ion affinities. 241,242 Development of even bulkier ligands is also expected, but in order to enforce non-classical geometries by repulsion, strong (attractive) dispersion donors such as aryl groups must be avoided. 25,29,243,244 Studies revealing the influence of geometry on stoichiometric and catalytic reactivity described in preceding sections have to-date focused exclusively on molecular systems.…”