Dipodal Ferrocene-Based Adsorbate Molecules for Self-Assembled Monolayers on Gold

Abstract

1,1′-Difunctionalised ferrocene derivatives have been studied, which contain groups suitable for chemisorption on gold substrates, namely [BOND]NC, [BOND]PR2 as well as a range of sulfur-containing units like [BOND]NCS, [BOND]SR, and thienyl. Thin films on gold have been fabricated from solution with most of these adsorbate species. Film thickness, composition and structure were investigated primarily by X-ray photoelectron and near-edge X-ray absorption fine-structure spectroscopy. The quality of self-assembled monolayers fabricated from 1,1′-diisocyanoferrocene (1) and 1,1′-diisothiocyanatoferrocene (2) turned out to be superior to that of films based on the other adsorbate species investigated. In addition to the surface coordination behaviour of 1 towards gold substrates, relevant aspects of the molecular coordination chemistry of 1 have also been addressed, including the synthesis and characterisation of [(μ-1){Cr(CO)5}2], Ag2(μ-1)22⋅H2O and [(μ-1)(AuCl)2]. The crystal structure of the gold complex is governed by aurophilic interactions and can be taken as a model for the arrangement of 1 in self-assembled monolayers on gold.