Showing papers by "Craig S. Lent published in 2015"
TL;DR: A combination of UV/Vis-NIR spectroscopic and TD-DFT computational studies indicate that electron transfer within Fc(+) FcC2 B9 (-) is achieved through a bridge-mediated mechanism, providing the possibility of an all-neutral null state for the implementation of quantum-dot cellular automata (QCA) molecular computing.
Abstract: The preparation of 7-Fc(+) -8-Fc-7,8-nido-[C2 B9 H10 ](-) (Fc(+) FcC2 B9 (-) ) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed-valence Fe(II) /Fe(III) complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis-NIR spectroscopic and TD-DFT computational studies indicate that electron transfer within Fc(+) FcC2 B9 (-) is achieved through a bridge-mediated mechanism. This electronic framework therefore provides the possibility of an all-neutral null state, a key requirement for the implementation of quantum-dot cellular automata (QCA) molecular computing. The adhesion, ordering, and characterization of Fc(+) FcC2 B9 (-) on Au(111) has been observed by scanning tunneling microscopy.
53 citations
TL;DR: In this article, the authors studied indole-2-carboxylic acid and carboxyly acid monolayers on gold using ultrahigh-vacuum scanning tunneling microscopy.
Abstract: Monolayers of indole-2-carboxylic acid and indole-3-carboxylic acid on gold are studied using ultrahigh-vacuum scanning tunneling microscopy. Both molecules form symmetric, cyclic, hydrogen-bonded pentamers, a structure that is stabilized by the presence of a weak hydrogen-bond donor (NH or CH) adjacent to the carboxylic acid on the five-membered ring. In addition to pentamers, indole-2-carboxylic acid forms hexamers and catemer chains, while indole-3-carboxylic acid monolayers are generally disordered. Density functional theory calculations show that pentamers and hexamers have stability comparable to dimers or short catemers. The coexistence of all of these structures likely arises from the nonequilibrium conditions present in solution during pulse deposition of the monolayer.
19 citations
TL;DR: The majority of adsorbed Fc(COOH)2 is instead found in six-molecule clusters with a well-defined and chiral geometry, showing that solution-phase species are determinative of adsorbate distribution for this system under these reaction conditions.
Abstract: Low-temperature scanning tunneling microscopy is used to observe self-assembled structures of ferrocenedicarboxylic acid (Fc(COOH)2) on the Au(111) surface. The surface is prepared by pulse-deposition of Fc(COOH)2 dissolved in methanol, and the solvent is evaporated before imaging. While the rows of hydrogen-bonded dimers that are common for carboxylic acid species are observed, the majority of adsorbed Fc(COOH)2 is instead found in six-molecule clusters with a well-defined and chiral geometry. The coverage and distribution of these clusters are consistent with a random sequential adsorption model, showing that solution-phase species are determinative of adsorbate distribution for this system under these reaction conditions.
15 citations
TL;DR: In this article, the authors point out that the driving force for charge localization in molecular QCA is the Coulomb interaction between neighboring molecules rather than nuclear relaxation, which suggests a different criterion for the relevant charge localization, one based on the electron transfer matrix element and the driving bias of a neighboring molecule.
12 citations