Cycloaddition reactions of acrylonitrile on the Si(100)-2 x 1 surface.

Cheol Ho Choi,Mark S Gordon

doi:10.1021/ja020147l

Cheol Ho Choi, Mark S Gordon

Open Access

PDF Available

https://doi.org/10.1021/ja020147l

Copy DOI

Export

Save

Cite

Abstract
Highlights/Summary
Full-Text PDF
Similar Papers

Abstract

Listen

Multi-reference as well as single-reference quantum mechanical methods were adopted to study the potential energy surface along three possible surface reaction mechanisms of acrylonitrile on the Si(100)-2 x 1 surface. All three reactions occur via stepwise radical mechanisms. According to the computed potential energy surfaces, both [4+2] and [2+2](CN) cycloaddition products resulting from the reactions of surface dimers with the C[triple bond]N of acrylonitrile are expected, due to the negligible activation barriers at the surface. Another possible surface product, [2+2](CC), requires a 16.7 kcal/mol activation energy barrier. The large barrier makes this route much less favorable kinetically, even though this route produces the thermodynamically most stable products. Isomerization reactions among the surface products are very unlikely due to the predicted large activation barriers preventing thermal redistributions of the surface products. As a result, the distribution of the final surface products is kinetically controlled leading to a reinterpretation of recent experiments. An intermediate Lewis acid-base type complex appears in both the [4+2] and [2+2](CN) cycloadditions entrance channels, indicating that the surface may act as an electrophile/Lewis acid toward a strong Lewis base substrate.

Highlights

With the advances of new experimental techniques and the development of increasingly sophisticated quantum mechanical methods and computational hardware, increasing effort is being expended to develop synthetically modified semiconductor surfaces
Many saturated and unsaturated organic and organometallic compounds are actively being tested for the creation of new interfacial chemical bonds that would potentially add new functionalities to the semiconductor technology
A large reaction barrier is expected along the symmetric reaction pathway

Summary

Introduction

With the advances of new experimental techniques and the development of increasingly sophisticated quantum mechanical methods and computational hardware, increasing effort is being expended to develop synthetically modified semiconductor surfaces. Subsequent theoretical studies[10] provided further support for the existence of the competing reactions by showing that there exists a low-energy [2+2] cycloaddition pathway on the Si(100) surface, and that the surface isomerization reaction connecting [4+2] and [2+2] products is very unlikely due to a high activation barrier. Recent experiments by Tao et al.[12] suggest that acrylonitrile reacts only through the CtN bond with Si dimers via a [2+2] cycloaddition mechanism, yielding exclusively the [2+2]CN surface product This conclusion is in contrast to the surface reactions of the homonuclear conjugated diene systems as considered earlier, for which both [2+2] and [4+2] products were observed. An extensive theoretical study of the potential energy surface of the reaction mechanisms is performed to elucidate the nature and origin of the Si(100)2×1 surface selectivity toward acrylonitrile, a heteronuclear diene

Computational Details

Results and Discussions

Conclusions