Molecular recognition of a self-assembled monolayer of a polydithiocarbamate derivative of beta-cyclodextrin on silver

The synthesis and molecular recognition properties of a new sulfur containi ng beta-cyclodextrin (beta-CD) derivative chemisorbed on a silver surface a re described. Hepta-6-amino-6-deoxy-beta-CD was allowed to react with CS2 i n the presence of ammonia to give a mixture of partially substituted dithio carbamate derivatives with an average degree pf substitution of 4.5. A modi fied silver electrode with this derivative is capable of discriminating bet ween the three positional isomers of nitrobenzoate ion and nitrophenol, as determined by cyclic voltammetry. Only the meta- and para-isomers give a si gnal corresponding to the reduction of the nitro group. This is attributed to the different orientations of the nitro group with respect to the silver surface after inclusion in the CD cavity. Experiments in the presence of c yclohexanol showed a decrease in signal intensity of the meta- and para-iso mers which is associated with the competitive complexation of this guest, s uggesting that the electroactive probe is complexed to the cavity. (C) 1999 Elsevier Science S.A. All rights reserved.