Electron transfer reactions of self-assembled monolayers of thio(phenylacetylene)(n)-substituted chiral metal-salen complexes

摘要

This paper describes immobilization of salen ligands in self-assembled monolayers (SAMs) on gold surfaces. The two salen ligands were attached to the gold surface via thio(phenylacetylene)(n) (n = 1, 2) substituents. The resulting SAMs have been analyzed using ellipsometry and X-ray photoelectron spectroscopy. These measurements showed that high-density monolayers formed on the gold surface (0.20 and 0.30 nmol/cm(2) for n = 1 and 2, respectively). (MnCl)-Cl-III, (CoCl)-Cl-III, and (FeCl)-Cl-III were incorporated in the core of the salen ligands immobilized on a gold electrode. The electron-transfer reactions of these metal-salen monolayers were studied by cyclic voltammetry in tetrahydrofuran, and reversible redox reactions between M-III and M-II (M = Mn, Co, and Fe) were observed under anaerobic conditions. In the presence of oxygen, the Mn-salen complex underwent an irreversible two-electron reduction. The coverage of the electroactive metal-salen complexes varied from 0.04 to 0.18 nmol/cm(2) depending on the metal. For all three metals, higher coverage values were obtained for the longer (phenylacetylene)(n) linker (n = 2) than for the shorter (n = 1). [References: 39]