Programmable dynamic covalent nanoparticle building blocks with complementary reactivity† †Electronic supplementary information (ESI) available: Synthetic procedures and characterization data for all compounds and nanoparticles (in situ and ex situ NMR, TEM, TGA, LDI-MS); stability tests on AuNP-6; kinetic analysis experimental methods and data for all experimental replicates; nanoparticle assembly experimental methods and monitoring by UV-Vis absorption spectroscopy, dynamic light scattering an

• Published in: Chemical science (Cambridge) Vol. 11; no. 2; pp. 372 - 383
• Main Authors: Marro, Nicolas, della Sala, Flavio, Kay, Euan R.
• Format: Journal Article
• Language: English
• Published: Royal Society of Chemistry 14.11.2019
• Subjects: Chemistry
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c9sc04195h

A toolkit of two complementary dynamic covalent nanoparticles enables programmable and reversible nanoparticle functionalization and construction of adaptive binary assemblies. Nanoparticle-based devices, materials and technologies will demand a new era of synthetic chemistry where predictive principles familiar in the molecular regime are extended to nanoscale building blocks. Typical covalent strategies for modifying nanoparticle-bound species rely on kinetically controlled reactions optimised for efficiency but with limited capacity for selective and divergent access to a range of product constitutions. In this work, monolayer-stabilized nanoparticles displaying complementary dynamic covalent hydrazone exchange reactivity undergo distinct chemospecific transformations by selecting appropriate combinations of ‘nucleophilic’ or ‘electrophilic’ nanoparticle-bound monolayers with nucleophilic or electrophilic molecular modifiers. Thermodynamically governed reactions allow modulation of product compositions, spanning mixed-ligand monolayers to exhaustive exchange. High-density nanoparticle-stabilizing monolayers facilitate in situ reaction monitoring by quantitative 19 F NMR spectroscopy. Kinetic analysis reveals that hydrazone exchange rates are moderately diminished by surface confinement, and that the magnitude of this effect is dependent on mechanistic details: surface-bound electrophiles react intrinsically faster, but are more significantly affected by surface immobilization than nucleophiles. Complementary nanoparticles react with each other to form robust covalently connected binary aggregates. Endowed with the adaptive characteristics of the dynamic covalent linking process, the nanoscale assemblies can be tuned from extended aggregates to colloidally stable clusters of equilibrium sizes that depend on the concentration of a monofunctional capping agent. Just two ‘dynamic covalent nanoparticles’ with complementary thermodynamically governed reactivities therefore institute a programmable toolkit offering flexible control over nanoparticle surface functionalization, and construction of adaptive assemblies that selectively combine several nanoscale building blocks.