Biasing mixed-valence transition metal complexes in search of bistable complexes for molecular computing

Mixed-valence ruthenium complexes as possible quantum-dot cellular automata (QCA) devices are discussed with respect to the effects of a driver, or biasing charge, on the system. The hybrid density functional method B3LYP was used with a 3-21G basis set, the only all-electron basis set available for ruthenium. Three different mixed-valence complexes have been investigated as representatives of each Robin and Day class, class I, II, and III. The input and output of a QCA device is not current, but charge polarization. The more localized classes, I and II, displayed the largest amount of polarization, while the more delocalized class III complex displayed the least polarization. This type of computational analysis can be extended to study the effects of different bridging and ancillary ligands, therefore this type of analysis is useful in the design of better molecular implementations of QCA devices.