Molecular QCA cells. 2. Characterization of an unsymmetrical dinuclear mixed-valence complex bound to a Au surface by an organic linker

Utilization of binary information encoded in the charge configuration of quantum-dot cells (the quantum-dot cellular automata, QCA, paradigm) requires surface-bound molecule-sized dots for room temperature operation. Molecular QCA cells are mixed-valence complexes, and the evaluation of a surface-bound unsymmetrical, heterobinuclear, two-dot, Fe-Ru molecular QCA cell is described. The tailed complex, trans-[Ru(dppm)(2)(C[triple bond]CFc)(N[triple bond]CCH(2)CH(2)-NH(2))][PF(6)] (dppm = methylbis(diphenylphosphane), Fc = (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))), is covalently modified with the molecular adapter, HS(CH(2))(10)COOH, for binding to a Au surface. Preparation and characterization of the films by AFM, XPS, and electrochemical techniques are reported. Cyclic voltammetric techniques are used to assess film growth, coverage and uniformity, effects of thiol diluents on areal densities of the complex, and stabilities of the accessible redox states. Amperometric techniques are used to investigate the efficiency of both chemical and electrochemical oxidation in producing the mixed-valence dication on the surface.