Experimental and Density Functional Theory Analysis of Serial Introductions of Electron-Withdrawing Ligands into the Ligand Shell of a Thiolate-Protected Au-25 Nanoparticle

Joseph F. Parker, Katarzyna A. Kacprzak, Olga Lopez-Acevedo, Hannu Hakkinen, Royce W. Murray*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The progress of ligand exchange reactions between the ligands of Au-25(SR)(18)(-) nanoparticles (SR = S(CH2)(2)Ph) and thiols with electron-withdrawing substituents (HSPh-p-X; X = Br, NO2) was monitored using nuclear magnetic resonance. As the reactions proceed, the introduction of the electron withdrawing SPhX ligands into the nanoparticle ligand shell causes a shift of the nanoparticle redox waves (Au25(1+/0)) and Au-25(0/1-)) to more positive potentials. Combining the NMR and electrochemical results reveals a nearly linear shift of the redox formal potentials as a function of the average number of exchanged ligands: similar to 42 and 25 mV/ligand for X = NO2 and Br, respectively. Using a simple model electron-withdrawing ligand (-SCH2Cl), density functional theory (DFT) was used to study in detail the effects on the nanoparticle electronic structure caused by exchange of this ligand for -SCH3. The calculations show how the electronegative X group changes the polarization of the nanoparticle and the chargedistribution among the ligands, the protecting (-SR-Au-SR-Au-SR) semirings, and the Au-13 core. The HOMO-LUMO gap is unchanged by the ligand exchanges; both states are equally stabilized by the presence of each incoming ligand, by 60 mV/ligand. Charge analysis suggests no significant changes in the Au-13 core, even after complete exchange. Rather, the charge is transferred inside the ligands, mostly from nearest-neighbor atoms of the semirings.

Original languageEnglish
Pages (from-to)8276-8281
Number of pages6
JournalJournal of Physical Chemistry C
Volume114
Issue number18
DOIs
Publication statusPublished - 13 May 2010
MoE publication typeA1 Journal article-refereed

Keywords

  • CRYSTAL-STRUCTURE
  • REDOX POTENTIALS
  • ELECTROCHEMISTRY
  • SUBSTITUENT
  • CLUSTER
  • LUMINESCENCE
  • COMPLEXES
  • ENERGIES
  • SYSTEM
  • AU-38

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