Spontaneously absorbed monolayers: anthrquinones and osmium polypyridyl complexes as molecular 'building blocks'

摘要

The synthesis and characterisation of a series of osmium polypyridyl complexes and the characterisation of a variety of anthraquinones is described, along with the fabrication and of gold, platinum and mercury microelectrodes The methods of characterisation include HPLC, UV-Visable spectroscopy, 'H-NiVIR and Cyclic voltammetry and Chronoamperometry.ududMonolayers of osmium polypyridyl complexes and anthraquinones were found to adsorb from micromolar solutions of the respective compounds dissolved in their appropriate solvent, In respect to the osmium complexes adsorption occurred through the free pendant nitrogen present on the ligand while adsorption for the anthraquinone was by means of an interaction with the electrode surface. The microenvironments of the osmium polypyridyl complexes were found to be sensitive to both the type and concentration of electrolytic species in solution with perchlorate ions being the most strongly ion-paired. Osmium polypyridyl monolayers also proved to highly solvated at saturation coverages with the double layer setting up within the immobilised film.ududSpontaneous adsorption of single and binary anthraquinone monolayers of anthraquinone- 2-7-disulphonic acid (2,7-AQDS) and l-chloro-4-hydroxy-anthraquinone (1,4-AQClOH) revealed that the adsorbates interact laterally within both single- and two-component monolayers with the concentration dependence of the surface coverage being adequately described by the Frumkin adsorption isotherm over the concentration range 1 - 3 0 |iM. The formal potentials, saturation surface coverages, free energies of adsorption and Frumkin interaction parameters are all affected by co-adsorption of the second quinone suggesting that dissimilar adsorbates interact laterally, most likely through intermolecular hydrogen bonding. Analysis of anthraquinone monolayers of l-amino-2-sulphonic-4- hydroxy-anthraquinone [AQNH2SOH] revealed that at coverages were the inter-site separation of the adsorbates was at a minimum and during electrochemical switching of the redox state of the adsorbed film, the voltammetry altered from the ideal response resulting in the presence of a sharp spike. Analysis of this anomaly illustrated extensive lateral adsórbate interaction resulting in the formation of an intermolecular hydrogen bonded network at saturation coverages.