Monolayer growth and exchange kinetics for alkylamines on the high-temperature superconductor YBa₂Cu₃O_7-δ

Using redox-active alkylamine adsorbates, we have studied monolayer growth and adsorbate-adsorbate exchange kinetics on YBa₂Cu₃O_7-δ. Herein we show that the formation kinetics for monolayers of FcC-(O)NH(CH₂)₄NH₂[Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)] do not follow typical Langmuir adsorption isotherm behavior. Specifically, a parabolic tailing in the isotherms has been attributed to the diffusion of adsorbates through the porous material. The displacement of surface-adsorbed FcC(O)NH(CH₂)₄NH₂ by another redox-active alkylamine, Fc(CH₂)₆NH₂, has been studied and determined to be a reversible and dynamic process. Concentration dependence studies suggest that the exchange takes place via an associative process involving surface Cu(II) sites. The lability of the surface-adsorbed alkylamine `ligands' and the proposed exchange mechanism are consistent with the solution coordination chemistry of Cu(II).