Controlling the rate of electron transfer between a quantum dot and a tri-ruthenium molecular cluster by tuning the chemistry of the interface

Adam J. Morris-Cohen, Kenneth O. Aruda, Andrew M. Rasmussen, Gabriele Canzi, Tamar Seideman, Clifford P. Kubiak, Emily A. Weiss

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Ultrafast transient absorption measurements reveal that the rate of photoinduced electron transfer (PET) from colloidal CdSe quantum dots (QDs) to oxo-centered triruthenium clusters (Ru 3O) depends on the structure of the chemical headgroup by which the Ru 3O clusters adsorb to the QDs. Complexes comprising QDs and Ru 3O clusters adsorbed through a pyridine-4-carboxylic acid ligand (nic-Ru 3O) have an intrinsic PET rate constant of (4.9 ± 0.9) × 10 9 s -1 whereas complexes comprising QDs and Ru 3O clusters adsorbed through a 4-mercaptopyridine ligand (thiol-Ru 3O) have an intrinsic PET rate constant of (36 ± 7) × 10 9 s -1. Cyclic voltammetry measurements of nic-Ru 3O and thiol-Ru 3O yield reduction potentials vs. Ag/AgCl of -0.93 V for both clusters, and density functional theory calculations of the nic-Ru 3O and thiol-Ru 3O clusters yield internal reorganization energies for the cluster radical anion of -0.17 eV and -0.19 eV, respectively. The small differences in driving force and reorganization energy between the two complexes rule out these parameters as possible explanations for the factor-of-seven difference in the rate constants for PET. The difference in the observed rates of PET for the two complexes is therefore attributable to a difference in donor-acceptor electronic coupling, which, according to electronic structure calculations, is modulated by the torsional angle between the Ru 3O core of the cluster and the functionalized pyridine ligand that bridges the cluster to the QD surface. This journal is

Original languageEnglish
Pages (from-to)13794-13801
Number of pages8
JournalPhysical Chemistry Chemical Physics
Volume14
Issue number40
DOIs
Publication statusPublished - Oct 28 2012

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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