A density functional theory study of enantiospecific adsorption at
chiral surfaces

A density functional theory study of enantiospecific adsorption at chiral surfaces
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by Z. Sljivancanin, K.V. Gothelf, and B. Hammer

J. Am. Chem. Soc. **124**, 14789-14794 (2002).

Abstract
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Density functional theory calculations are carried out for the
adsorption of a chiral molecule, *(S)*- and
*(R)*-HSCH:sub:`2`\ CHNH\ :sub:`2`\ CH\ :sub:`2`\ P(CH\ :sub:`3`)\ :sub:`2`,
on a chiral surface, Au(17 11 9)\ :sup:`S`. The *S*-enantiomer is found
to bind more strongly than the *R*-enantiomer by 8.8 kJ/mol, evidencing
that the chiral nature of the kink sites at the Au(17 11 9) surface
leads to enantiospecific binding. Adsorption of two related chiral
molecules, HSCH\ :sub:`2`\ CHNH\ :sub:`2`\ COOH ("cysteine") and
HSCH\ :sub:`2`\ CHNH\ :sub:`2`\ CH\ :sub:`2`\ NH\ :sub:`2`, does,
however, not lead to enantiospecific binding. The results of the density
functional calculations are broken down into a local binding model in
which each of the chiral molecule's three contact points with the
surface provides a contribution to the overall adsorption bond strength.
The enantiospecific binding is demonstrated to originate from the
simultaneous optimization of these three *local* bonds. In the model the
deformation energy costs of both the molecule and the surface are
further included. The model reveals that the molecule may undergo large
deformations in the attempt to optimize the three bonds while the
surface deforms to a lesser extent. The most favorable binding
configurations of each enantiomer are, however, characterized by small
deformation energies only, justifying a local binding picture.