Characterization of self assembled thiolated β-cyclodextrin and tolane thioacetate mixed monolayer

Abstract

In the molecular electronic devices, the diphenylacetylene, namely tolane (TT) derivatives have been shown the possibility of functioning as an unbiased controller by changing angle of one phenyl ring with respect to the other. For fabrication of these molecules into a molecular device, TT should be assembled with sufficient, regularly spaced arrangement and precisely controlled orientation on the solid substrates. In order to arrange TT molecules with controlled orientation and exact spacing, we constructed a molecular structure with two components system; TT as the molecular electronic component and the other is a surface reactive dithiolated β-cyclodextrin (β-CD) as a spacer between adjacent tolanes. β-CD formed a self-assembled monolayer (SAM) while TT chemisorbed at the void space formed by direct contact of three β-CD molecules on the surface. Unlike most of β-CD applications, the cavity of β-CD was filled with ferrocene prior to form SAM to avoid formation of inclusion complex of TT with β-CD. Surface concentration of β-CD and TT was estimated from cyclic voltammetric measurement of ferrocene. Fourier transform infrared-reflection absorption spectroscopy (FTIR-RAS), and electroanalytical method were used for structural characterization of the mixed SAM of β-CD and TT.