Electric properties molecular electrostatic potential

Significant efforts have been made to assemble teratogenic data basses with peer-reviewed evaluations (ref. 1). New avenues for the SAR studies have been opened, such as quantitative methods for structural superposition of molecules and for superposition of their reactivity characteristics (ref. 2). Emphasis has been placed on the electrostatic properties of the molecules, such as the molecular electrostatic potential, the electric fields, and the polarizability terms calculated from perturbation expansions (ref. 2). Computer-assisted multivariate SAR which deals with many variables simultaneously has been advanced (ref. 3). 

A major advantage of fluorescence as a sensing property stems from the sensitivity to the precise local environment of the intensity, i.e., quantum yield (excited state lifetime (xf), and peak wavelength (Xmax). In particular, it is the local electric field strength and direction that determine whether the fluorescence will be red or blue shifted and whether an electron acceptor will or will not quench the fluorescence. An equivalent statement, but more practical, is that these quantities depend primarily on the change in average electrostatic potential (volts) experienced by the electrons during an electronic transition (See Appendix for a brief tutorial on electric fields and potentials as pertains to electrochromism). The reason this is more practical is that even at the molecular scale, the instantaneous electric... 

The radial deformation of the valence density is accounted for by the expansion-contraction variables (k and k ). The ED parameters P, Pim , k, and k are optimized, along with conventional crystallographic variables (Ra and Ua for each atom), in an LS refinement against a set of measured structure factor amplitudes. The use of individual atomic coordinate systems provides a convenient way to constrain multipole populations according to chemical and local symmetries. Superposition of pseudoatoms (15) yields an efficient and relatively simple analytic representation of the molecular and crystalline ED. Density-related properties, such as electric moments electrostatic potential and energy, can readily be obtained from the pseudoatomic properties [53]. 

Za is the charge on nucleus A, located at Ra, and p(r) is the electronic density function, which we compute from the molecular wave function. V(r) is commonly termed the "electrostatic" potential, as molecular systems are most practically treated as static distributions of electronic charge around rigid nuclear frameworks. It is a real physical property which expresses the net electrical effect of the nuclei and electrons at each point in space r, and it has emerged as an effective tool for studying molecular reactive behavior [34-37]. An important feature of V(r) is that it can be determined experimentally by diffraction methods [37-39], as well as computationally. 

Some of the terms included in the Breit-Pauli Hamiltonian also describe small interactions that can be probed experimentally by inducing suitable excitations in the electron or nuclear spin space, giving rise to important contributions to observable NMR and ESR parameters. In particular, for molecular properties for which there are interaction mechanisms involving the electron spin, also the spin-orbit interaction (O Eqs. 11.13 and O 11.14) becomes important The Breit-Pauli Hamiltonian in O Eqs. 11.5-11.22, however, only includes molecule-external field interactions through the presence of a scalar electrostatic potential 0 (and the associated electric field F) and the appearance of the magnetic vector potential in the mechanical momentum operator (O Eq. 11.23). In order to extract in more detail the interaction between the electronic structure of a molecule and an external electromagnetic field, we need to consider in more detail the form of the scalar and vector potentials. 

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