Molecule-Based Electronics

Valence shell electron pair repulsion (VSEPR) model (Section 110) Method for predicting the shape of a molecule based on the notion that electron pairs surrounding a central atom repel one another Four electron pairs will arrange them selves in a tetrahedral geometry three will assume a trigo nal planar geometry and two electron pairs will adopt a linear arrangement... 

Frontier Orbitals and Chemical Reactivity. Chemical reactions typically involve movement of electrons from an electron donor (base, nucleophile, reducing agent) to an electron acceptor (acid, electrophile, oxidizing agent). This electron movement between molecules can also be thought of as electron movement between molecular orbitals, and the properties of these electron donor and electron acceptor orbitals provide considerable insight into chemical reactivity. 

The intramembranous domain of Ca -ATPase contains of the mass of the ATPase molecule based on electron microscopy of Ca -ATPase crystals [90,91] and X-ray diffraction analysis of oriented multilayers of sarcoplasmic reticulum [140]. Although in speculative models developed from these reconstructed structures the intramembranous domain was pictured as containing ten transmembrane helices [141,142], at the resolution attainable so far, several alternative transmembrane arrangements would be equally possible. 

Figure 1.10 The tetrahedral, trigonal pyramidal, and angular geometries of the methane, ammonia, and water molecules based on the tetrahedral arrangement of four electron pairs.

The use of organic polymers as conductors and semiconductors in the electronics industry has led to a huge research effort in poly(thiophenes), with a focus on the modification of their electronic properties so that they can behave as both hole and electron conductors. Casado and co-workers [60] have performed combined experimental and theoretical research using Raman spectroscopy on a variety of fluorinated molecules based on oligomers of thiophene, an example of one is shown in Figure 7. 

To date, most small molecule-based OLEDs are prepared by vapor deposition of the metal-organic light-emitting molecules. Such molecules must, therefore, be thermally stable, highly fluorescent (in the solid state), form thin films on vacuum deposition, and be capable of transporting electrons. These properties limit the number of metal coordination compounds that can be used in OLED fabrication. 

In this and the next sections we discuss two groups of molecule-based conducting magnets at which the %-d interaction works effectively. The first approach is the use of quasi one-dimensional electronic systems as the re-electron layers, and the other strategy is to increase the magnitude of the %-d interaction by the introduction of intermolecular halogen-halogen contacts. 

Second, in designing new molecule-based electronic devices, one of the major goals is the precise control of the current flowing between the terminals. Electrochemical molecular junctions allow for control of the potentials of the electrodes with respect to the redox potential of incorporated redox-active molecules with well-defined, accessible, tunable energy states. These junctions represent unique systems able to predict precisely at which applied potential the current flow will take off. Even though the presence of a liquid electrolyte represents a detriment towards possible applications, they provide the concepts for designing molecular devices that mimic electronic functions and control electrical responses. 

Haick H, Cahen D (2008) Contacting organic molecules by soft methods towards molecule-based electronic devices. Acc Chem Res 41 359-366... 

Molecule-based electronics evolved from several research areas ... 

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