Scheme 1. Synthetic Strategy for Immobilization of a Ru(II) Polypyridyl Chromophore, 12+, on nanoITO or nanoTiO2 Electrodes Based on (i) Silane Surface Functionalization and (ii) CuAAC Click Chemistry

Silane and Click Chemistry

Binding functional molecules to nanostructured mesoporous metal oxide surfaces provides a way to derivatize metal oxide semiconductors for applications in dye-sensitized photoelectrosynthesis cells, DSPECs. The commonly used anchoring groups, phosphonates and carboxylates, are unstable as surface links to oxide surfaces at neutral and high pH, leading to rapid desorption of appended molecules.

Published in ACS Applied Materials & Interfaces, researchers from the Thomas J. Meyer group, in collaboration with colleagues from Shenzhen University's College of Chemistry & Environmental Engineering, describe a synthetically versatile molecular attachment strategy based on initial surface modification with a silyl azide followed by click chemistry. This technique has been used for the stable installation of surface-bound metal complexes, and the resulting surfaces are highly stabilized toward complex loss with excellent thermal, photochemical, and electrochemical stabilities.

The procedure involves binding 3-azidopropyltrimethoxysilane, APTMS, to nanostructured mesoporous TiO2 or tin-doped indium oxide, ITO, electrodes by silane attachment followed by azide-terminated, Cu(I)-catalyzed azide-alkyne cycloaddition, CuAAC, reactions with an alkyne-derivatized ruthenium(II) polypyridyl complex.

The chromophore-modified electrodes display enhanced photochemical and electrochemical stabilities compared to phosphonate surface binding with extended photoelectrochemical oxidation of hydroquinone for more than similar to approximately 6 h with no significant decay.