Charge-Transfer Effects in Ligand Exchange Reactions of Au25 Monolayer-Protected Clusters.
Reported here are second-order rate constants of associative ligand exchanges of Au25L18 nanoparticles (L = phenylethanethiolate) of various charge states, measured by proton nuclear magnetic resonance at room temperature and below. Differences in second-order rate constants (M(-1) s(-1)) of ligand exchange (positive clusters ∼1.9 × 10(-5) versus negative ones ∼1.2 × 10(-4)) show that electron depletion retards ligand exchange. The ordering of rate constants between the ligands benzeneselenol > 4-bromobenzene thiol > benzenethiol reveals that exchange is accelerated by higher acidity and/or electron donation capability of the incoming ligand. Together, these observations indicate that partial charge transfer occurs between the nanoparticle and ligand during the exchange and that this is a rate-determining effect in the process.
Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
Tessa M
TM
Carducci
Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
Raymond E
RE
Blackwell
Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
Royce W
RW
Murray
NMR; charge state; nanoparticle; rate constant; selenolate