METAL-ION COMPLEXATION AND ELECTRON-DONOR PROPERTIES OF DIOCTADECYLDITHIOCARBAMATE IN MONOLAYERS AT THE GAS WATER INTERFACE AND IN ORGANIZED MONOLAYER SYSTEMS

Dioctadecyldithiocarbamate (DOTC), incorporated in monolayers and organized monolayer assemblies, forms complexes with metal ions present in an adjacent aqueous phase. Surface pressure/area, surface potential/area isotherms, and surface enhanced UV-vis reflection spectroscopy at the gas/water interface have been used for the characterization and investigation of the DOTC-metal ion complexation. The formation of DOTC-metal complexes leads to changes in the area per molecule and the surface potential of the DOTC monolayers as well as to either a shift or the appearance of a new band in the UV-vis reflection and absorption spectra. Complexation data for mono-, bi-, and trivalent metals ions are presented. In the multilayer assemblies on solid substrates, the complexation was monitored using UV-vis absorption spectroscopy. Metal complex forming properties of DOTC should serve as the basis for the development of metal ion sensors. DOTC monolayers have been found to be stable even on acidic subphases in contrast to the behavior of short chain derivatives of dithiocarbamate in aqueous solution. In addition to the metal ion complexation properties, DOTC exhibits pH dependent electron donor properties at the gas/water interface and in monolayer assemblies. In mixed monolayers of DOTC and an amphiphilic electron acceptor tetracyanoquinodimethane (C18TCNQ) we have observed the formation of ionic charge transfer (CT) complexes.