Bridge Length-Dependent Ultrafast Electron Transfer from Re Polypyridyl Complexes to Nanocrystalline TiO2 Thin Films Studied by Femtosecond Infrared Spectroscopy

John B. Asbury, Encai Hao, Yongqiang Wang, Tianquan Lian

Research output: Contribution to journalArticle

186 Scopus citations

Abstract

Femtosecond infrared spectroscopy was used to study the electron injection dynamics of Re(CO)3CI(dcbpy) (ReC0A) and related derivatives on the surface of TiO2 nanocrystalline thin films. We prepared two derivatives of ReC0A by inserting 1 and 3 CH2 spacers (ReClA and ReC3A respectively) between the bipyridine rings and the carboxylate anchoring groups. We directly observed electron injection from the excited states of Re dyes to TiO2 by simultaneously measuring the broad absorption of injected electrons and the vibrational spectrum of the complex in its ground, excited, and oxidized states. Electron injection from ReC0A to TiO2 was found to occur on the <100-fs time scale, whereas the excited state vibrational spectrum evolved with a time constant of a few picoseconds, indicating that injection occurred before complete vibrational relaxation in this system. We found that the electron injection rate decreased by a factor of >200 from ReCOA to ReClA. This decrease is much larger than the predicted change for nonadiabatic electron transfer (ET) processes, in which ET rate depends exponentially on the length of CH2 spacers. This result as well as ultrafast injection rate indicate an adiabatic electron injection process in ReC0A-sensitized TiO2. In contrast, the electron injection rate decreased by a factor of 13.7 from ReClA to ReCSA, which agrees qualitatively with the trend predicted for nonadiabatic ET processes.

Original languageEnglish (US)
Pages (from-to)11957-11964
Number of pages8
JournalJournal of Physical Chemistry B
Volume104
Issue number50
StatePublished - Dec 21 2000

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Bridge Length-Dependent Ultrafast Electron Transfer from Re Polypyridyl Complexes to Nanocrystalline TiO<sub>2</sub> Thin Films Studied by Femtosecond Infrared Spectroscopy'. Together they form a unique fingerprint.

  • Cite this