Document Detail

Surface S(N)2 reaction by H2O on chlorinated Si(100)-2 x 1 surface.
MedLine Citation:
PMID:  16852328     Owner:  NLM     Status:  PubMed-not-MEDLINE    
The potential energy surfaces of one, two, and three water molecule sequential adsorptions on the symmetrically chlorinated Si(100)-2 x 1 surface were theoretically explored with SIMOMM:MP2/6-31G(d). The first water molecule adsorption to the surface dimer requires a higher reaction barrier than the subsequent second water molecule adsorption. The lone pair electrons of the incoming water molecule nucleophilically attack the surface Si atom to which the leaving Cl group is bonded, yielding an S(N)2 type transition state. At the same time, the Cl abstracts the H atom of the incoming water molecule, forming a unique four-membered ring conformation. The second water molecule adsorption to the same surface dimer requires a much lower reaction barrier, which is attributed to the surface cooperative effect by the surface hydroxyl group that can form a hydrogen bond with the incoming second water molecule. The third water molecule adsorption exhibits a higher reaction barrier than the first and the second water molecule adsorption channels but yields a thermodynamically more stable product. In general, it is expected that the surface Si-Cl bonds can be subjected to the substitution reactions by water molecules, yielding surface Si-OH bonds, which can be a good initial template for subsequent surface chemical modifications. However, oversaturations can be a competing side reaction under severe conditions, suggesting that the precise control of surface kinetic environments is necessary to tailor the final surface characteristics.
Hee Soon Lee; Ki-Seok An; Yunsoo Kim; Cheol Ho Choi
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  109     ISSN:  1520-6106     ISO Abbreviation:  J Phys Chem B     Publication Date:  2005 Jun 
Date Detail:
Created Date:  2006-07-20     Completed Date:  2007-06-21     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  10909-14     Citation Subset:  -    
Department of Chemistry, College of Natural Sciences, Kyungpook National University, Taegu 702-701, South Korea.
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