Exploring the Scope of cluster-surface reactive Ag-Nanocluster

Nils Hermann Vogeler, The University of Western Ontario

Abstract

Nanomaterials like nanoparticles or nanoclusters are finding more interest in applications of material science, medicine and catalysis. The field of nanocluster research continues to provide new structures of differing stoichiometries and properties. New cluster frameworks can be targeted by altering the synthetic conditions or the stabilizing surface ligands. The direct synthesis of cluster species and the ligand exchange reactions on the clusters bring problems with them, that can lead to changes in composition as well as the decomposition of the desired cluster. Much less focus has been on modifying cluster surfaces post-synthesis while maintaining the cluster core. Our group’s recent efforts have been directed at preparing metal nanoclusters with reactive surface substrates to serve as templates and exploring the cluster-surface reactivity to alter their function post-synthesis while maintaining the core structure.

This work targets atomically precise CO₃^2- templated Ag₂₀ nanoclusters (NCs) with 8 and 6 surface moieties containing reactive surface functionalities based on the previous reported [CO₃@Ag₂₀(StBu)₁₀((NO₃)₈(DMF)₄] by Gao et al.. To synthesize these Ag₂₀NC`s the procedure for the preparation of [CO₃@Ag₂₀(StBu)₁₀((NO₃)₈(DMF)₄] was modified with the addition of desired functional benzoate derivatives (O₂CC₆H₄-R) that substitute the surface nitrate ions. In this thesis, the family of cluster surface-reactive [CO₃@Ag₂₀(StBu)₁₀((O₂CC₆H₄-R)_8-x(NO₃)_x(DMF)₄] was elaborated to include photochemically reactive cluster-surface moieties and here is described the synthesis, photochemical isomerization of aryl-azo-groups, trifluoromethyl-aryldiazirine moieties for the generation of reactive carbene on the cluster surface of the Ag₂₀-moiety, and perfluorinated phenylazide capable of subsequent cluster surface (CS) functionalization via click reactions.

The surface aryl-azo-groups were used to investigate the photostability of the Ag₂₀ core as well as the isomerization of the azo bond between its Z and E isomers. The trifluoromethyl-aryldiazirine Ag₂₀-NC provides a photochemical route to cluster surface reactive carbenes that insert into X-H bonds and add to alkenes to deliver functionality for applications for catalysis and medicine. The perfluorinated phenylazide surface functionality was used to show with model phosphines the possibility for surface click reaction via Staudinger and Staudinger-Bertozzi ligations to decorate the cluster surface under mild conditions for application in medicine or catalysis.