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The enolpyridine, OH-ketoenamime, NH equilibrium in crystals of 1,3-bis(pyridin-2-yl)propan-2-one is studied using temperature-dependent single-crystal x-ray diffraction. The report states that the theoretical model suggest the appearance of concerted hydrogen motions, which are unique to the dimer and can be used to quantify the effect of the supramolecular interaction on the hydrogen population in the crystal.

A new numerical method is introduced for the solution of Poisson's equation for the electrostatic potential between arbitrarily shaped boundary surfaces that may appear in the metal-molecule-metal junctions. This method is based on a straightforward procedure in which the arbitrarily shaped system is embedded in a cubic box.

A brief review of the clock-based definition of the tunneling traversal time is presented. The applicability of the tunneling time concept to resonant tunneling processes, within a simple one-dimensional double barrier model, is discussed.

The enolpyridine, OH-ketoenamime, NH equilibrium in crystals of 1,3-bis(pyridin-2-yl)propan-2-one was studied using temperature-dependent single-crystal X-ray diffraction. The relative population of the different tautomers was found to be sensitive to the temperature in the range of 100-300 K, illustrating the small thermodynamic difference between these two tautomers. This energy resemblance is partially aft ributed to the molecular packing in the crystal, where the molecules are arranged in the form of dimers. Ab initio electronic energy calculations (HF/6-31 G** and MP2/6-31 G**) reveal the effect of dimerization in the crystal on the electronic energy levels. Several tautomeric states were identified in the dimer of 1,3- bis(pyridin-2-yl)propan-2-one. A model is proposed in which four of these dimer states are populated in the crystal at ambient temperatures. The crystallographic data were treated according to this four-state dimer model, suggesting that the free energy of the OH-NH dimers is higher than that of the OH-OH dimers by 120 ± 10 cal mol-1 and that the NH-NH dimers are yet higher in free energy by 50 ± 10 cal mol-1. [ABSTRACT FROM AUTHOR]

Weak fluctuations about the rigid equilibrium structure of ordered molecular bridges drive charge transfer in donor-bridge-acceptor systems via quantum unfurling, which differs from both hopping and ballistic transfer, yet static disorder (low frequency motions) in the bridge is shown to induce a change of mechanism from unfurling to hopping when local fluctuations along the molecular bridge are uncorrelated. Remarkably, these two different transport mechanisms manifest in similar charge-transfer rates, which are nearly independent of the molecular bridge length. We propose an experimental test for distinguishing unfurling from hopping in DNA models with different helix directionality. A unified formulation explains the apparent similarity in the length dependence of the transfer rate despite the difference in the underlying transport mechanisms.

The semiconductor device industry is constantly challenged by the demands of miniaturization. Therefore, the use of nanomaterials, such as quantum dots (QDs), is expected. At these scales, quantum effects are anticipated under industrial working conditions. Here, we present a simple fabrication method for integrating colloidal coupled QDs as components in a vertical device. Characterization of the fundamental properties of QDs as an ensemble of isolated particles and as layered QD hybrid structures is demonstrated. For the case of layered QD hybrid structures, coupling between dots is on average stronger with typical energy band gaps reduced by more than 200 meV. The shown device offers a straightforward method to measure and establish a strong coupling transport system under ambient conditions., Competing Interests: The authors declare no competing financial interest.

Colloidal quantum dots are free-standing nanostructures with chemically tunable electronic properties. In this work, we consider a new STM tip-double quantum dot (DQD)-surface setup with a unique connectivity, in which the tip is coupled to a single dot and the coupling to the surface is shared by both dots. Our theoretical analysis reveals a unique negative differential resistance (NDR) effect attributed to destructive interference during charge transfer from the DQD to the surface. This NDR can be used as a sensitive probe for interdot interactions in DQD arrays.

The slow response of electronic components in junctions limits the direct applicability of pump-probe type spectroscopy in assessing the intramolecular dynamics. Recently the possibility of getting information on a sub-picosecond time scale from dc current measurements was proposed. We revisit the idea of picosecond resolution by pump-probe spectroscopy from dc measurements and show that any intramolecular dynamics not directly related to charge transfer in the current direction is missed by current measurements. We propose a pump-probe dc shot noise spectroscopy as a suitable alternative. Numerical examples of time-dependent and average responses of junctions are presented for generic models.

Colloidal quantum dots (CQDs) are free-standing nanostructures with chemically tunable electronic properties. This combination of properties offers intriguing new possibilities for nanoelectromechanical devices that were not explored yet. In this work, we consider a new scanning tunneling microscopy setup for measuring ligand-mediated effective interdot forces and for inducing motion of individual CQDs within an array. Theoretical analysis of a double quantum dot structure within this setup reveals for the first time voltage-induced interdot recoil and dissociation with pronounced changes in the current. Considering realistic microscopic parameters, our approach enables correlating the onset of mechanical motion under bias voltage with the effective ligand-mediated binding forces.