Lattice-gas modeling of enantioselective adsorption by template chiral substrates

The general behavior of enantioselective adsorption by templated chiral substrates is studied in the framework of lattice-gas and random sequential adsorption theories. The template is assumed to be formed by randomly preadsorbing a chiral species A on a square lattice of sites. A second chiral probe species, B, thus performs a random sequential adsorption process on the templated substrate and the enantioselectivity of the process with respect to one of the B enantiomers is obtained as a function of the relevant parameters of the model. All species considered in the present study are considered as monomers, i.e., they occupy a single adsorption site. In an extension of the simple model, the possibility that the chiral probe species can themselves act as templates is taken into account. It is shown how different arrangements of A molecules on the surface generate different enantioselectivities as a function of coverage, some of which have been observed experimentally.