Ruthenium Tetraammine Chemistry of Self-Assembled Monolayers on Gold Surfaces: Substitution and Reactivity at the Monolayer Interface

Abstract

Different methods for preparing a variety of trans-tetraammine−ruthenium complexes on self-assembled monolayer (SAM) surfaces on gold electrodes are described. The neutral complex, trans-[RuII(NH3)4(SO3)(H2O)], was bound directly to terminal pyridine or imidazole groups on preformed SAM surfaces and oxidized to form trans-[RuIII(NH3)4(SO4)(PyMeNH)]−SAM surfaces. The kinetics of substitution of trans-[RuII(NH3)4(SO3)(H2O)] onto pyridine and imidazole groups on preformed SAM surfaces and the ligand substitution of N-heterocycles (such as isonicotinamide, imidazole, and other biological molecules such as ATP (adenosine triphosphate)) on the resulting ruthenium(III) SAM surfaces were studied and found to be slightly slower than those for the corresponding reactions in aqueous solutions. The rate of substitution of the ruthenium(II) complexes onto terminal pyridine or imidazole groups on preformed SAM surfaces depends greatly on the charge of the ruthenium complex, with faster substitution occurring for neutra...