INDEX electronic properties

Last but not least, the thianthrenes, derived from a ring system that is rapidly increasing in importance because of its electronic properties, are reviewed by Joule. Readers are reminded that this volume will contain no index. The last index volume was Volume 46, and we now plan to designate every fifth volume an index volume thus the next will be Volume 51. 

Log P and MR are considered thermodynamic descriptors, pR a combined thermodynamic and electronic index, and a an electronic property index, E is designed to account for steric effects. Corrections for non-additivity, based upon the chemical bonding topology, have been suggested and used. These include proximity, bond type, ring, and group shape correction features. (8-10)... 

Material Properties Bibliographic Data Purdue University Purdue University (CINDAS) thermophysical, mechanical, and electronic properties of materials bibliographic references and author index... 

In contrast, EET has been historically modelled in terms of two main schemes the Forster transfer [15], a resonant dipole-dipole interaction, and the Dexter transfer [16], based on wavefunction overlap. The effects of the environment where early recognized by Forster in its unified theory of EET, where the Coulomb interaction between donor and acceptor transition dipoles is screened by the presence of the environment (represented as a dielectric) through a screening factor l/n2, where n is the solvent refractive index. This description is clearly an approximation of the global effects induced by a polarizable environment on EET. In fact, the presence of a dielectric environment not only screens the Coulomb interactions as formulated by Forster but also affects all the electronic properties of the interacting donor and acceptor [17],... 

Two of the hydrophihcity scales in Table 2 were derived from experimental measures of the behavior of amino acids in various solvents, namely partitioning coefficients [K-D index of Kyte and Doolittle (30)] or mobility in paper chromatography [Rf index of Zimmerman et al. (31)]. By contrast, the Hp index was obtained from quantum mechanics (QM) calculations of electron densities of side chain atoms in comparison with water (32). The Hp index is correlated highly with these two established hydrophobicity scales (Table 4). Therefore, like the polarizability index, it is possible to represent fundamental chemical properties of amino acids (hydrophUicity, Hp) with parameters derived from ab initio calculations of electronic properties. However, in contrast to polarizabihty (steric effects), hydrophihcity shows significant correlation with preference for secondary structure. Thus, hydrophobic amino acids prefer fi-strands (and fi-sheet conformations) and typically are buried in protein structures, whereas hydrophilic residues are found commonly in turns (coil structure) at the protein surface. 

IlMei et al. (39) derived the VHSE5 composite index of electronic effects. This scale (Vectors of Hydrophobic, Steric, and Electronic properties) was derived from principal components analysis of 50 different physico-chemical variables. 

Several scales presented in Table 3 show promise as measures of fundamental electronic properties of amino acids as does the Hp index of hydrophilicity. Nevertheless, additional improvements are desirable. The polarizability index of steric effects should include hyperconjugation as a component. Clearly, the movement of electrons into antibonding orbitals contributes to molecular deformation (24). The Hp index is based on PM3 calculations of electron densities for the component atoms of amino acid side chains. A more integrative approach with higher-order theory is likely to refine this measure additionally. 

The electronic properties of Pt particles on different supports and in zeolites of different proton concentrations were also probed with the competitive hydrogenation of toluene and benzene (276). It was found that the ratio of the adsorption coefficients of toluene and benzene hr/6b, which can be obtained from a kinetic analysis of the hydrogenation rate data, can be used as a convenient empirical index for the electronic environment of Pt particles. For Pt in zeolite Y, the ratio was found to increase with increasing acidity, as does the electron deficiency. This trend was rationalized by considering that toluene is a stronger electron donor than benzene. 

The Kronecker delta functions, 5 and 6,p, resulting from Eq. [21], cannot be simplified to 1 or 0 because the indices p and q may refer to either occupied or virtual orbitals. The important point here, however, is that the commutator has reduced the number of general-index second-quantized operators by one. Therefore, each nested commutator from the Hausdorff expansion of H and T serves to eliminate one of the electronic Hamiltonian s general-index annihilation or creation operators in favor of a simple delta function. Since f contains at most four such operators (in its two-electron component), all creation or annihilation operators arising from f will be eliminated beginning with the quadruply nested commutator in the Hausdorff expansion. All higher order terms will contain commutators of only the cluster operators, T, and are therefore zero. Hence, Eq. [52] truncates itself naturally after the first five terms on the right-hand side. ° This convenient property results entirely from the two-electron property of the Hamiltonian and from the fact that the cluster opera-... 

A molecular descriptor defined in analogy with the Dosmorov complexity index, also accounting for electronic properties of molecules [Bonchev, 1983] ... 

High-resolution in situ STM as well as phase transition dynamics of nucleobases on Au(lll) and other low-index electrode surfaces supported by infrared spectroscopy have been reviewed recently by Nichols and coworkers [142] and Wandlowski and coworkers [143]. We refer to these reviews for details and note instead another aspect of single-molecule dynamics of DNA-based molecules. The observed electronic conductivity of oligonucleotides of variable length and variable base composition has opened almost a Pandora s box of novel DNA-based electronic properties. These include particularly photochemical and interfacial electrochemical ET. We refer to other recent reviews [144, 145] for this, still far from settled, issue but note the following STM-based studies that illuminate the conductivity issue at the single-molecule level (Figure 2.4). 

The dectrotopological state index (Si) is an extension of the purely topological index [55]. Electronic properties (i.e., the charge distribution in the molecule) are also considered. Atoms with identical T may differ in their Si. Electrotopological state indices have been used successfully to predict physico-chemical data, such as basicity (pJCa) or Hpophilicity (logP), as well as for quantitative structure-activity relationship (QSAR) or QSPR studies. 

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