Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 10, 2013 | Supplemental Material
Journal Article Open

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

Files

ja402495e_si_001.pdf
Files (1.9 MB)
Name Size Download all
md5:5a16bc8dc2344a172db017949b817343
1.9 MB Preview Download

Additional details

Created:
August 19, 2023
Modified:
October 24, 2023