Efficient Synthesis of Isoxazolidine-Tethered Monolayer-Protected
Gold Nanoparticles (MPGNs) via 1,3-Dipolar Cycloadditions under
High-Pressure Conditions
Jun Zhu,Brandon M. Lines,Michael D. Ganton,Michael A. Kerr, andMark S. Workentin*
Department of Chemistry, The University of Western Ontario, London, ON, Canada N6A 5B7
mworkent@uwo.ca
Received November 12, 2007
Abstract:
A maleimide-modified 2.5 ± 0.5 nm mixed monolayer protected gold nanoparticle (2-C12MPGN)
containing approximately 30% maleimide-terminated dodecanethiolate/dodecanethiolate ligands was
prepared. The 2-C12MPGN was reacted with a series of nitrones (a-i) at both atmospheric and hyperbaric
(11 000 atm) conditions to form the corresponding isoxazolidine-modified nanoparticles (3-C12MPGN)
via an interfacial 1,3-dipolar cycloaddition. At atmospheric pressures, the reaction proceeds slowly (if at
all) and makes this reaction impractical for the synthetic modification of the nanoparticles. However, by
performing the reaction under the high-pressure conditions, the reaction proceeds efficiently and
quantitatively. TEM shows that the use of high pressure does not affect the size of the gold nanoparticle
core. The 3-C12MPGNs were characterized by 1H NMR spectroscopy by comparing the spectra obtained
with those of model reactions utilizing N-dodecylmaleimide (4) with the same nitrones (a-i) to form 5.
Additionally, the cycloaddition reaction also occurs more readily with 4 than with 2-C12MPGN with all
nitrones, indicating that the environment of the latter affects the cycloaddition reaction.
