Heck Coupling of Olefins to Mixed Methyl/Thienyl Monolayers on Si(111) Surfaces
Abstract
The Heck reaction has been used to couple olefins to a Si(111) surface that was functionalized with a mixed monolayer comprised of methyl and thienyl groups. The coupling method maintained a conjugated linkage between the surface and the olefinic surface functionality, to allow for facile charge transfer from the silicon surface. While a Si(111) surface terminated only with thienyl groups displayed a surface recombination velocity, S, of 670 ± 190 cm s^(–1), the mixed CH_3/SC_4H_3–Si(111) surfaces with a coverage of θ_(SC_4H_3) = 0.15 ± 0.02 displayed a substantially lower value of S = 27 ± 9 cm s^(–1). Accordingly, CH_3/SC_4H_3–Si(111) surfaces were brominated with N-bromosuccinimide, to produce mixed CH_3/SC_4H_2Br–Si(111) surfaces with coverages of θ_(Br–Si) < 0.05. The resulting aryl halide surfaces were activated using [Pd(PPh_3)_4] as a catalyst. After activation, Pd(II) was selectively coordinated by oxidative addition to the surface-bound aryl halide. The olefinic substrates 4-fluorostyrene, vinylferrocene, and protoporphyrin IX dimethyl ester were then coupled (in dimethylformamide at 100 °C) to the Pd-containing functionalized Si surfaces. The porphyrin-modified surface was then metalated with Co, Cu, or Zn. The vinylferrocene-modified Si(111) surface showed a linear dependence of the peak current on scan rate in cyclic voltammetry, indicating that facile electron transfer had been maintained and providing evidence of a robust linkage between the Si surface and the tethered ferrocene. The final Heck-coupled surface exhibited S = 70 cm s^(–1), indicating that high-quality surfaces could be produced by this multistep synthetic approach for tethering small molecules to silicon photoelectrodes.
Additional Information
© 2013 American Chemical Society. Received: March 10, 2013; Published: June 26, 2013. This work was supported by the National Science Foundation (CHE-1214152) and the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology. The Link Foundation Energy fellowship (L.E.O.), the NSF ACC-F (M.J.R., CHE-1042009), and the John and Maria Laffin Trust SURF (T.X.D.) are gratefully acknowledged for graduate, postdoctoral, and undergraduate fellowship support. We acknowledge Dr. Ronald Grimm and Ms. Judith Lattimer for insightful discussions.Attached Files
Supplemental Material - ja402495e_si_001.pdf
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Additional details
- Eprint ID
- 40989
- Resolver ID
- CaltechAUTHORS:20130829-095118486
- NSF
- CHE-1214152
- Caltech Beckman Institute
- Link Foundation
- NSF
- CHE-1042009
- John and Maria Laffin Trust
- Caltech Summer Undergraduate Research Fellowship (SURF)
- Created
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2013-08-29Created from EPrint's datestamp field
- Updated
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2023-03-16Created from EPrint's last_modified field