(481d) Surface Plasmon Resonance Spectroscopy As a Tool for Distinguishing Homogeneous Versus Heterogeneous Catalytic Pathways for Metal Nano-Catalyzed C-C Coupling Reactions

Carbon-Carbon (C-C) coupling reactions are the most widely used reactions used for making variety of molecules, including polymers and pharmaceuticals. These reactions have been traditionally carried out using homogeneous, expensive and toxic palladium (Pd) catalysts. Nano-metal catalyzed cross-coupling reactions will have several advantages as they can be used as a platform to develop energy efficient and environmentally friendly flow processes. Recently, promising results have been reported in the literature on the use of less toxic metal nanocatalysts such as gold (Au) and copper (Cu) for cross-coupling reactions. However, identifying the catalytic pathway (i.e., heterogeneous versus homogeneous pathway) and monitoring the stability of functioning nanocatalysts remain highly challenging tasks.

In this contribution, we show that localized surface plasmon resonance (LSPR) spectroscopy can be used as platform to distinguish homogeneous and heterogeneous pathways, and monitor stability of functioning nanocatalysts in nano-metal catalyzed cross-coupling reactions. Using finite-difference time-domain (FDTD) optical simulations, we show the use of UV-Vis extinction spectra to distinguish catalytic pathways and monitor nanoparticle stability. We demonstrate that for a variety of nanocatalysts including monometallic catalysts (e.g., Au, Pd and Cu), and bimetallic core/shell nanocatalysts (e.g., Au/Pd and Ag/Pd), there is a measurable SPR peak shift, change in SPR intensity and full-width at half-maximum (FWHM) in the surface plasmon extinction spectrum. This novel and simple UV-Vis surface plasmon spectroscopic technique will help to (a) fundamentally understand the catalytic pathway, and (b) develop environmental friendly metal nanocatalysts for C-C, C-N, C-S and C-O coupling reactions.

Reference

1. Mohammadparast et.al “C-C Coupling Reactions Catalyzed by Gold Nanoparticles: Evidence for Substrate-Mediated Leaching of Surface Atoms Using Localized Surface Plasmon Resonance Spectroscopy”, J. Phys. Chem. C, 2019, In press. https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.8b12453