Dye-sensitized electron transfer from TiO2 to oxidized triphenylamines that follows first-order kinetics

Two sensitizers, [Ru(bpy) 2 (dcb)] 2+ ( RuC ) and [Ru(bpy) 2 (dpb)] 2+ ( RuP ), where bpy is 2,2′-bipyridine, dcb is 4,4′-dicarboxylic acid-2,2′-bipyridine and dpb is 4,4′-diphosphonic acid-2,2′-bipyridine, were anchored to mesoporous TiO 2 thin films and utilized to sensitize the reaction of TiO 2...

Full description

Saved in:
Bibliographic Details
Published in:Chemical science (Cambridge) 2018-01, Vol.9 (4), p.94-949
Main Authors: DiMarco, Brian N, Troian-Gautier, Ludovic, Sampaio, Renato N, Meyer, Gerald J
Format: Article
Language:English
Subjects:
Chemistry
Electron transfer
Electrons
Kinetics
Rate constants
Reaction kinetics
Thin films
Titanium dioxide
Titanium oxides
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Two sensitizers, [Ru(bpy) 2 (dcb)] 2+ ( RuC ) and [Ru(bpy) 2 (dpb)] 2+ ( RuP ), where bpy is 2,2′-bipyridine, dcb is 4,4′-dicarboxylic acid-2,2′-bipyridine and dpb is 4,4′-diphosphonic acid-2,2′-bipyridine, were anchored to mesoporous TiO 2 thin films and utilized to sensitize the reaction of TiO 2 electrons with oxidized triphenylamines, TiO 2 (e − ) + TPA + → TiO 2 + TPA, to visible light in CH 3 CN electrolytes. A family of four symmetrically substituted triphenylamines (TPAs) with formal E o (TPA +/0 ) reduction potentials that spanned a 0.5 eV range was investigated. Surprisingly, the reaction followed first-order kinetics for two TPAs that provided the largest thermodynamic driving force. Such first-order reactivity indicates a strong Coulombic interaction between TPA + and TiO 2 that enables the injected electron to tunnel back in one concerted step. The kinetics for the other TPA derivatives were non-exponential and were modelled with the Kohlrausch-William-Watts (KWW) function. A Perrin-like reaction sphere model is proposed to rationalize the kinetic data. The activation energies were the same for all of the TPAs, within experimental error. The average rate constants were found to increase with the thermodynamic driving force, consistent with electron transfer in the Marcus normal region. Two sensitizers, [Ru(bpy) 2 (dcb)] 2+ ( RuC ) and [Ru(bpy) 2 (dpb)] 2+ ( RuP ), were anchored to mesoporous TiO 2 thin films and utilized to sensitize the reaction of TiO 2 electrons with oxidized triphenylamines to visible light in CH 3 CN electrolytes.
ISSN:2041-6520
2041-6539
DOI:10.1039/c7sc03839a