Molecular wires bands

Materials that are comprised of small fragments of (SN) with organic terminal groups, e.g., ArSsNaAr and ArS5N4Ar (Ar = aryl), are of potential interest as molecular wires in the development of nanoscale technology. Consistent with simple band theory, the energy gap... 

All the emission spectra in solution showed a maximum peak with a shoulder on the red side. It was observed that the photoluminescence A.max in dilute THF solution red shifted from 470 to 474. They also exhibited similar Stokes shifts (about 66 nm) due to their similar backbone. The fluorescence quantum yields ( F) of these molecular wires in dilute THF solution were measured to be 0.25 for 470,0.22 for 471,0.20 for 472,0.20 for 473, and 0.18 for 474, respectively. The excited-state lifetime for OTEs was found to be single-exponential within a few hundred picoseconds. However, in THF solution (10 17 M), the decay of the emission maximum band for these molecular wires was found to be biexponential with two excited-state lifetimes yielding a c2 of <1.2. One excited-state lifetime ranged from 0.42 to 0.30 ns, which was in agreement with that in OTEs. Another one exhibited a... 

The absorption spectra of every molecular wire 470-474 in thin films were nearly identical to those in solution, which implied that the interchain interaction and/or intermolecular aggregation in the ground states might be suppressed in films possibly owing to truxene moieties with hexyl substituents. Their absorption spectra in films show an identical peak at about 309 nm owing to the n n electron absorption band of the truxene units. The absorption Xmax peaked at 400 nm for 470, 410 nm for 471, 415 nm for 472, 418 nm for 473, and 424 nm for 474, respectively. 

First, we will first discuss the "bulk" molecular devices which have been popular, even though they are molecular devices only in the larger sense (i.e. because of the band structure of the solids, or because of phase change properties, or other bulk effects). Second, a small detour is made to discuss electron transfer within the primary reaction center in photosynthesis, and the controlling factors in intramolecular electron transfer. Third, we will concentrate on the truly unimolecular devices. Fourth and last, a discussion on molecular "wires" and connectors is given. 

Localization/delocalization is an important concept in a wider perspective. We may think of a molecular wire where alkali has been added and donated to the wire. Conductivity assumes that electrons are not trapped. The condition is that A>K (class 111) for each FT step, otherwise the conductivity will be low. The latter condition is therefore the condition for delocalized electrons. It is often believed that a repetitive system together with unfilled orbital bands is a satisfactory condition for delocalization (metals). However, even if infinite orbitals may be constructed, they are less useful in a quantum description, if the electrons are trapped. 

Figure 11. A two-dimensional modulated electron channel showing molecular wires addressing an electron gas. The molecular wires generate a two-dimensional band structure in the gas. The source-drain current is therefore sensitive to signals (charge/light) arriving along the columns the integer n denotes the quantum well states in the substrate gas.

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