Click chemistry in ultra-high vacuum - tetrazine coupling with methyl enol ether covalently linked to Si(001)

TL;DR

This study demonstrates a novel additive-free click reaction between tetrazine and enol ether in ultra-high vacuum, enabling covalent bonding on silicon surfaces with potential for advanced organic synthesis.

Contribution

It introduces a new UHV-compatible click chemistry method linking tetrazine to silicon surfaces without additives, confirmed by experimental and theoretical analysis.

Findings

Reaction occurs at 380 K as shown by XPS.

No direct binding of tetrazine to Si(001) detected.

Density functional theory supports a moderate energy barrier.

Abstract

The additive-free tetrazine/enol ether click reaction was performed in ultra-high vacuum (UHV) with an enol ether group covalently linked to a silicon surface: Dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate molecules were coupled to the enol ether group of a functionalized cyclooctyne which was adsorbed on the silicon (001) surface via the strained triple bond of cyclooctyne. The reaction was observed at a surface temperature of 380 K by means of X-ray photoelectron spectroscopy (XPS). No indications for tetrazine molecules which bind directly to the Si(001) surface via the nitrogen atoms were detected. A moderate energy barrier was deduced for this click reaction in vacuum by means of density functional theory based calculations, in good agreement with the experimental results. This UHV-compatible click reaction thus opens a new, flexible route for synthesizing covalently bound organic architectures.