Modular “Click” Chemistry for Electrochemically and Photoelectrochemically Active Molecular Interfaces to Tin Oxide Surfaces

Abstract

We demonstrate the use of "click" chemistry to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) nanoparticle thin films. By using photochemical grafting to link a short-chain alcohol to the surface followed by conversion to a surface azide group, we enable use of the Cu(I)-catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC) reaction, a form of "click" chemistry, on metal oxide surfaces. Results are shown with three model compounds to test the surface chemistry and subsequent ability to achieve electrochemical and photoelectrochemical charge transfer. Surface-tethered ferrocene groups exhibit good electron-transfer characteristics with thermal rates estimated at >1000 s(-1). Time-resolved surface photovoltage measurements using a ruthenium terpyridyl coordination compound demonstrate photoelectron charge transfer on time scales of nanoseconds or less, limited by the laser pulse width. The results demonstrate that the CuAAC "click" reaction can be used to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) and other metal oxide semiconductors.

CuAAC-based assembly and characterization of a ruthenium–copper dyad containing a diimine–dioxime ligand framework

“…For these reasons, CuAAC has been applied to the construction of sophisticated molecular architectures in order to study photoinduced processes 21–23. This strategy has been particularly utilized for the functionalization of ruthenium polypyridine photoactive units24 by various organic moieties,25–27 nickel28, 29 or iron30 complexes and for their attachment onto surfaces 31–33. However, to the best of our knowledge, CuAAC has never been employed to assemble a Ru tris-diimine photosensitizer with a copper complex, although copper also displays interesting redox properties.…”

Optically Functionalized Grid‐Type Complexes by a Post‐Assembly Strategy

“…This allows for modification and diversification in a post‐synthetic or post‐assembly approach while keeping the grid and the attached molecules separate to avoid changing the electronic properties and therefore complexation behavior of the ligand. While in general oligopyridines and oligopyridine complexes bearing alkyne or azide functionalities can be functionalized using the copper‐catalyzed CuAAC reaction this proved to be problematic in our case leading to the formation of insoluble precipitates and disassembly of the grid structure. Even though first attempts of copper‐free reactions with our grids and a SPAAC reagent were successful, we chose instead to pursue the use of electronically activated alkynes as the high costs, limited accessibility and steric demand of the resulting linkages of SPAAC octynes and similar reagents were seen as disadvantages.…”

Artificial photosynthesis with metal and covalent organic frameworks (MOFs and COFs): challenges and prospects in fuel‐forming electrocatalysis

“…Alternative functionalization strategies that result in highly stable interfaces include the photochemical grafting of alkenes on oxides surfaces such as ITO (Li and Zuilhof 2012), SnO 2 (Benson et al 2011) and TiO 2 (Franking et al 2009), as well as the electrochemical grafting of diazonium salts (Pinson and Podvorica 2005). Methods for suppressing often-observed multilayer formation during electrografting have been developed, and fast ICT can be achieved, possibly due to improved electronic coupling or the conjugated nature of the interface (Harris et al 2018b).…”