Towards a Molecular Electronics

The requisites for the supramolecular antenna sensitizers are (1) an efficient antenna effect, vectorially translating absorbed energy toward a molecular component and (2) the capability of the molecular component bound to the semiconductor surface to inject electrons into the semiconductor from its excited state. Antenna sensitizers can increase the fraction of light harvested by a sensitized semiconductor surface. Two simple prototypes, following the branched or onedimensional design, are shown schematically in Fig. 2. An a priori evaluation... 

Switching to a basis of orbitals allows us to proceed toward constructing the description of a molecular electronic structure based on the GF approximation under well acceptable restrictions. Indeed, let us assume that the multipliers in eq. (1.181) satisfy the additional condition of strong orthogonality ... 

The rediscovery of cytochromes by Keilin in 1925 led him to propose that the reduction of O2 is linked to the oxidation of reduced substrates by a series of redox reactions, carried out by cellular components collectively referred to as the respiratory electron-transport chain. Progress toward a molecular understanding of these redox reactions has been painfully slow. Most of the components are multisubunit proteins that reside in the inner mitochondrial membrane (Figure 6.11). These proteins (Complexes 1-IV) are quite difficult to purify with retention of in vivo properties, and they do not crystallize well. 

A further step towards switchable molecular electronic circuits is the light-controlled conductivity of 2-D lattices of gold nanoparticles bridged by photochromic diarylethene molecules [90]. This was demonstrated by van der Molen et al., who first prepared the device as described above [89] and then immersed it in a solution of on state switches so as to obtain an interlinked 2-D nanopartide array (see Figure 5.62a and b). In this case, the nanopartide array serves as a template for the switching molecules which form conductive bridges in-between. 

Mahmoud, A.M., Bergren, A.J., Pekas, N., and McCreery, R.L. (2011) Towards integrated molecular electronic devices characterization of molecular layer integrity during fabrication processes. Adv. Funct. Mater., 21, 2273-2281. 

Studies have shown that carbene reactivity toward a wide variety of substrates is dramatically affected by the nature and multiplicity of the electronic state. - Similarly, the structure, electronic state, thermochemical stability, and reaction kinetics of both singlet and triplet carbenes can be significantly affected by the R-substituents. If R provides steric hindrance, the carbene center can be shielded to slow down inter-molecular reactions (kinetic stabilization). Additionally, bulky and/or geometrically... 

The surface diffusion of defects and adsorbates is of obvious importance in heterogeneous catalysis, as this process brings the reactants together. Understanding the dynamics of molecules on oxide surfaces is also a key step toward the realization of working molecular electronics. We note here that diffusion of Ob-vacs really means diffusion of Ob into the vacancy, which leaves another Ob-vac in the position vacated by the Ob- Similarly, diffusion of OHb occurs by diffusion of the H atom. 

Chemiluminescence is defined as the production of light by chemical reactions. This light is cold , which means that it is not caused by vibrations of atoms and/or molecules involved in the reaction but by direct transformation of chemical into electronic energy. For earlier discussions of this problem, see 7 9h Recent approaches towards a general theory of chemiluminescence are based on the relatively simple electron-transfer reactions occurring in aromatic radical-ion chemiluminescence reactions 10> and on considerations of molecular orbital symmetry as applied to 1.2-dioxetane derivatives, which very probably play a key role in a large number of organic chemiluminescence reactions 11>. 

Formally, the lone pairs on molecular nitrogen, hydrogen cyanide, and carbon monoxide are sp hybrid orbitals, whereas NLMO hybridizations calculated even lower p contributions. Hence, these lone pairs have low directionality, the electron density remains close to the coordinating atom and interaction between the lone pair and the Be2+ is comparatively weak. The Be-L bonds are easily disrupted and ligand exchange consequently can proceed with a low activation barrier. A high degree of p character, on the other hand, means that the lone pair is directed toward beryllium, with electron density close to the metal center, and thus well suited for coordination. 

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