Specific electronic structure

It is not possible to introduce a nitro group into the 1,2,4-triazole ring by the action of the sulfuric-nitric acid mixture because of the disactivation of the cycle by two pyridine nitrogen atoms furthermore, their disactivation effect is aggravated by the heterocycle protonation in the acid medium. The only exception is the nitration of l,2,4-triazolon-5 [250-264], This is probably due to the specific electronic structure of the substrate (the azolone form) (Scheme 32). 

Since the van der Waals interaction is usually unspecific, any relative comparison, e.g. between adsorption energies at two different adsorption sites, should be determined by the chemical interaction and thus more or less reliably predicted by DPT. In this way it can be justified that we have used the results of DFT to confirm the experimentally found bridge site adsorption. Indeed, both LDA and GGA predict the bridge site to be the lowest energy adsorption site, but the adsorption energies themselves are vastly different ( b (LDA) =-5.99 eV/cell (GGA) = 150 meV/cell) [33]. Other relative properties which can be rationalised on the basis of DFT are the site-specific electronic structure or the distortion of the molecule (i.e. relative molecule-substrate interaction strength between different parts of the molecule). Moreover, STM images have been shown to be reliably reproduced by a Tersoff-Haman approach based on DFT-LDA calculations [33]. 

Presently, the simulation of real metal surfaces with defects of all sorts is hampered by the restriction of system size and also because only little quantitative information is available concerning the specific electronic structure near these defects and its consequences for the binding of water molecules and ions. However, first steps into this direction were made recently Siepmann and Sprik [51], who investigated the influence of surface topology on water/electrode systems, and by Nagy and Denuault [98, 99], who extended the platinum-water potential to defect surfaces. However, since they did not take into account the electronic structure of the metal, their approach is purely geometrical. 

The combination of the properties of nano-TiO and polyaniline enables to solve successfully the problems of the chemistry, physics and electronics. Specific electronic structures of the nano-TiO (as the n-type semiconductor) and polyaniline (as the electron s conductor in majority of the cases and as a p-type semiconductor under certain conditions) give the possibility to design the systems for different applications. For example, today such materials are equipped in the photocatalytic conversions of the different pollutants especially [7 4. The modification of the surface of TiO particles by polyanilines layers raises the catalytic activity of titanium (IV) oxide [5, 79]. Composite materials, which have integrated properties of 5-doped nano-TiO and polyaniline layers can be effective in the photo-catalytic processes especially. 

In this section, we will not discuss polarity-sensitive probes, the mechanism of which is based on the specific electronic structure (even though one of them, pyrene [19], belongs to the most widely used) and focuses on fluorophores used for monitoring the solvent relaxation after the transition of the probe to the electronically excited state [22]. Let us first briefly explain the mechanism of these fluorescent probes (Fig. 1). 

Electronic Excitation Although each atom has a specific electronic structure, the disnibution of electrons can be modified through the deposition of energy through photon, electron, or ion impact. The atom/ion then responds through either ... 

Analysis of electrostatic effects may be also useful tool in predicting activity of new inhibitors aiding conventional ligand design procedures, where specific electronic structure features are typically not taken into account. This will be illustrated by results obtained for some leucine aminopeptidase inhibitors [15. ... 

This approach allowed us to examine activity differences originating from specific electronic structure of inhibitors with modified phosphonic group at position 02. Fig. 7 presents correlation of the experimental activity of these compounds with the estimate of the total electrostatic energy of interactions calculated according to the formula ... 

For example, processes such as corrosion, adhesion, friction, and wear are all governed by the properties of the interacting surfaces. This is even more so for catalytic processes, on which the majority of industrial chemical processes is based today. The present chapter is devoted to simple metal surfaces. We will see how, even in these comparatively elementary systems, a surface introduces a qualitatively different behavior of electrons, bonds, and so on. The focus of the chapter is on the surface-specific electronic structure and its consequences. We start from very simple concepts and gradually incorporate more realistic features into our models in order to obtain an at least qualitative understanding of the generic electronic properties of metal surfaces. 

The surface-specific electronic structure may be accompanied by different, surface-confined magnetic properties. The surface-specific vibrational properties should be the cause of not only a different molar heat capacity at the surface compared to that of the bulk but also a different ease of atom displacement in terms of diffusion and, ultimately, melting. All these expectations have been verified during the past decades of surface science. Surface-specific electronic properties, magnetism, vibrations (phonons), diffusion coefficients, melting temperatures, and so on, have been experimentally proven. It is justified to say that surfaces need to be described by physical properties that hold only for a few surface-near atomic/molecular layers, and that are different from those of the bulk, that is, by a two-dimensional surface physics. Most such investigations have been carried out over the past four decades with sohd surfaces under UHV conditions. However, more recently, such investigations are extended to soft matter and hquid surfaces... 

---