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Issue 40, 2012
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Controlling the rate of electron transfer between a quantum dot and a tri-ruthenium molecular cluster by tuning the chemistry of the interface

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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 (Ru3O) depends on the structure of the chemical headgroup by which the Ru3O clusters adsorb to the QDs. Complexes comprising QDs and Ru3O clusters adsorbed through a pyridine-4-carboxylic acid ligand (nic-Ru3O) have an intrinsic PET rate constant of (4.9 ± 0.9) × 109 s−1 whereas complexes comprising QDs and Ru3O clusters adsorbed through a 4-mercaptopyridine ligand (thiol-Ru3O) have an intrinsic PET rate constant of (36 ± 7) × 109 s−1. Cyclic voltammetry measurements of nic-Ru3O and thiol-Ru3O yield reduction potentials vs. Ag/AgCl of −0.93 V for both clusters, and density functional theory calculations of the nic-Ru3O and thiol-Ru3O 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 Ru3O core of the cluster and the functionalized pyridine ligand that bridges the cluster to the QD surface.

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

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Publication details

The article was received on 15 Mar 2012, accepted on 23 Apr 2012 and first published on 23 Apr 2012


Article type: Paper
DOI: 10.1039/C2CP40827A
Citation: Phys. Chem. Chem. Phys., 2012,14, 13794-13801
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    Controlling the rate of electron transfer between a quantum dot and a tri-ruthenium molecular cluster by tuning the chemistry of the interface

    A. J. Morris-Cohen, K. O. Aruda, A. M. Rasmussen, G. Canzi, T. Seideman, C. P. Kubiak and E. A. Weiss, Phys. Chem. Chem. Phys., 2012, 14, 13794
    DOI: 10.1039/C2CP40827A

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