Electrostatic potential, molecular interactive interaction

In the next chapters, one or several of those formalisms are used to describe some aspects of molecular behavior toward other molecules in terms of properties such as electrostatic potential, nonbonded interactions, behavior in solvents, reactivity and behavior during interaction with other molecules, and finally similarity on the basis of nonquantum and quantum properties. 

Compared with the classical approach of Mulliken, the charges derived from an NAP are almost fully independent from the basis set utilized. Yet, the quality of the reproduc l molecular electrostatic potentials and interaction energies is often lower th that attained using Mulliken charges. ... 

A. J. Stone, Classical Electrostatics in Molecular Interactions , ed. Z. B. Maksic, Theoretical Models of Chemical Bonding , Vol. 4, Spinger Verlag, Berlin, 1991, pp. 103-131 A. J. Stone, Theoretical Models for Intermolecular Potentials , ed. J. L. Rivail, Modelling of Molecular Structures and Properties , Elsevier Science Publishers, Amsterdam, 1990, pp. 27-44. 

Knowledge of the spatial dimensions of a molecule is insufficient to imderstand the details of complex molecular interactions. In fact, molecular properties such as electrostatic potential, hydrophilic/lipophilic properties, and hydrogen bonding ability should be taken into account. These properties can be classified as scalar isosurfaces), vector field, and volumetric properties. 

These properties arc also relevant if molecular interactions arc considered. In contrast to electrostatic potentials, they only take effect at small distances between interacting molecular regions,... 

Non-covalent interactions between molecules often occur at separations where the van der Waals radii of the atoms are just touching and so it is often most useful to examine the electrostatic potential in this region. For this reason, the electrostatic potential is often calculated at the molecular surface (defined in Section 1.5) or the equivalent isodensity surface as shown in Figure 2.18 (colour plate section). Such pictorial representations... 

Electron distribution governs the electrostatic potential of molecules. The electrostatic potential describes the interaction of energy of the molecular system with a positive point charge. Electrostatic potential is useful for finding sites of reaction in a molecule positively charged species tend to attack where the electrostatic potential is strongly negative (electrophilic attack). 

Fig. 1.3 A survey of molecular properties molecular interaction fields MEPs, molecular based on their interdependence and the electrostatic potentials PK,...

The stereoelectronic features produce actions at a distance by the agency of the recognition forces they create. These forces are the hydrophobic effect, and the capacity to enter ionic bonds, van der Waals interactions and H-bonding interactions. The most convenient and informative assessment of such recognition forces is afforded by computahon in the form of MIFs, e.g. lipophilicity fields, hydrophobicity fields, molecular electrostatic potentials (MEPs) and H-bonding fields (see Chapter 6) [7-10]. 

Carrupt, P. A., El Tayar, N., Karlen, A., Testa, B. Value and limits of molecular electrostatic potentials for characterizing drug-biosystem interactions. Methods Enzymol. 1991, 203, 638-677. 

P.-A. Carrupt, N. El Tayar, A. Karlen, and B. Testa, Molecular Electrostatic Potential for Characterizing Drug-Biosystem Interactions, Academic Press, London, 1991, pp. 638-677. 

When the MM subsystem is being optimized, or a molecular dynamics simulation is being carried out on the MM subsystem, the QM/MM electrostatic interactions are approximated with fixed point charges on the QM atoms which are fitted to reproduce the electrostatic potential (ESP) of the QM subsystem [37],... 

Our discussion in this chapter will focus on the use of the electrostatic potential as a means to understanding and predicting chemical interactions. First, we will examine some of its properties and important features. Next, we will discuss methodology. Finally we will review some recent applications of the electrostatic potential in areas such as hydrogen bonding, molecular recognition, and understanding and prediction of a variety of physio-chemical properties related to molecular interactions. Our intent has not been to provide a complete survey of the ways in which the potential has been used, many of which are described elsewhere (Politzer and Daiker 1981 Politzer, Laurence, and Jayasuriya 1985 Politzer and Murray 1990 Politzer and Murray 1991 Politzer and Truhlar 1981 Scrocco and Tomasi 1973), but rather to focus on some diverse examples. 

The calculated molecular electrostatic potential is particularly well suited for the analysis of noncovaient interactions, which do not involve making or breaking covalent bonds and which occur without any extensive polarization or charge transfer between the interacting species. As we have discussed in the previous section, V(r) has been shown to be useful... 

In recent years, we have extended the nature of our analysis to include certain statistically defined features of the surface electrostatic potential. Our purpose has been to expand the capabilities of V(r) for quantitatively describing macroscopic properties that reflect non-covalent molecular interactions. This has led to the development of the General Interaction Properties Function (GIPF), described by Eq. (3.7) ... 

The macroscopic property of interest, e.g., heat of vaporization, is represented in terms of some subset of the computed quantities on the right side of Eq. (3.7). The latter are measures of various aspects of a molecule s interactive behavior, with all but surface area being defined in terms of the electrostatic potential computed on the molecular surface. Vs max and Fs min, the most positive and most negative values of V(r) on the surface, are site-specific they indicate the tendencies and most favorable locations for nucleophilic and electrophilic interactions. In contrast, II, a ot and v are statistically-based global quantities, which are defined in terms of the entire molecular surface. II is a measure of local polarity, °fot indicates the degree of variability of the potential on the surface, and v is a measure of the electrostatic balance between the positive and negative regions of V(r) (Murray et al. 1994 Murray and Politzer 1994). 

The first step in our procedure is to compute an optimized structure for each molecule and then to use this geometry to compute the electronic density and the electrostatic potential. A large portion of our work in this area has been carried out at the SCF/STO-5G //SCF/STO-3G level, although some other basis sets have also been used. We then compute V(r) on 0.28 bohr grids over molecular surfaces defined as the 0.001 au contour of the electronic density (Bader et al. 1987). The numbers of points on these grids are converted to surface areas (A2), and the and Fs min are determined. Our statistically based interaction in-... 

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