Non-Covalent Dimerization after Enediyne Cyclization on Au(111)

TL;DR

This study explores how enediyne molecules cyclize on gold surfaces and form non-covalent dimers, revealing new surface chemistry pathways and the role of non-covalent interactions in surface reactions.

Contribution

It demonstrates that C1-C6 cyclization occurs on Au(111), producing strained bicyclic olefins that self-assemble into non-covalent dimers, a novel surface chemistry insight.

Findings

C1-C6 cyclization is favored over C1-C5 on Au(111).

The C1-C6 product forms non-covalent dimers on the surface.

Density functional theory explains the non-covalent association mechanism.

Abstract

We investigate the thermally-induced cyclization of 1,2 - bis(2 - phenylethynyl)benzene on Au(111) using scanning tunneling microscopy and computer simulations. Cyclization of sterically hindered enediynes is known to proceed via two competing mechanisms in solution: a classic C1 - C6 or a C1 - C5 cyclization pathway. On Au(111) we find that the C1 - C5 cyclization is suppressed and that the C1 - C6 cyclization yields a highly strained bicyclic olefin whose surface chemistry was hitherto unknown. The C1 - C6 product self-assembles into discrete non-covalently bound dimers on the surface. The reaction mechanism and driving forces behind non-covalent association are discussed in light of density functional theory calculations.