Molecular QCA Cells. 1. Structure and Functionalization of an Unsymmetrical Dinuclear Mixed-Valence Complex for Surface Binding

Utilization of binary information encoded in the charge configuration of quantum-dot cells (the quantum-dot cellular
automata, QCA, paradigm) requires molecule-sized dots for room temperature operation. Molecular QCA cells are
mixed-valence complexes, and the evaluation and functionalization of an unsymmetrical heterobinuclear, two-dot,
Fe−Ru molecular QCA cell is described. The solid state structures of trans-RuCl(dppm)2(C⋮CFc) (1) (dppm =
methylbis(diphenylphosphane), Fc = (η5-C5H5)Fe(η5-C5H4)) and mixed-valence [trans-RuCl(dppm)2(C⋮CFc)][BF4]
(1a) as well as XPS and spectroscopic data suggest class II behavior suitable for the intended application. Utilization
of the trans-Cl position of 1 permits functionalization for surface binding. Two “tailed” complexes of 1, trans-Ru(dppm)2(C⋮CFc)(C⋮CPhOCH3) (2) and trans-[Ru(dppm)2(C⋮CFc)(N⋮CCH2CH2NH2)][PF6] (3), have been prepared
and characterized. The solid state structure of 3 and multinuclear NMR experiments define the structures. In addition,
the spectroscopic properties of all complexes and their mixed-valence species are used to define the effect of the
substituent “tail” on mixed-valence properties. Further, the electrochemistry of these compounds permits assessment
of the extent of perturbation of the substituents on the comproportionation constants and overall electrochemical
stability. The complexes possess properties necessary for candidate QCA molecules.