Electrostatic molecular

Momany F A 1978 Determination of partial atomic charges from ab initio molecular electrostatic potentials. Application to formamide, methanol and formic acid J. Phys. Chem. 82 592... 

Bonaccorsi ct al. [204 defined for the first time the molecular electrostatic potential (MEP), wdicli is dearly tfie most important and most used property (Figure 2-125c. The clcctro.static potential helps to identify molecular regions that arc significant for the reactivity of compounds. Furthermore, the MEP is decisive for the formation of protein-ligand complexes. Detailed information is given in Ref [205]. 

Charges Derived from the Molecular Electrostatic Potential... 

Cox S R and D E Williams 1981. Representation of the Molecular Electrostatic Potential by a New Atomic Charge Model. Journal of Computational Chemistry 2 304-323. 

Kurst G R, R A Stephens and R W Phippen 1990. Computer Simulation Studies of Anisotropic iystems XIX. Mesophases Formed by the Gay-Berne Model Mesogen. Liquid Crystals 8 451-464. e F J, F Has and M Orozco 1990. Comparative Study of the Molecular Electrostatic Potential Ibtained from Different Wavefunctions - Reliability of the Semi-Empirical MNDO Wavefunction. oumal of Computational Chemistry 11 416-430. 

M. P. Allen, D. J. Tildesley, Computer Simulation of Liquids Oxford, Oxford (1987). Chemical Applications of Atomic and Molecular Electrostatic Potentials P. Politzer, D. G. Truhlar, Eds., Plenum, New York (1981). 

CM Breneman, KB Wiberg. Determining atom-centered monopoles from molecular electrostatic potentials. The need for high sampling density m formamide conformational analysis. J Comput Chem 11 361-373, 1990. 

Fig. 3-2. Molecular electrostatic potential with 6-31G //3-21G basis set in the molecular plane of (ii)-nitrous acid. Black dots refer to four different protonation sites in potential minima. For values of isopotential contours see Nguyen and Hegarty, 1984.

It is worth to remark that the opposite also happens. There is an evolution in the experimental teehniques too, and in some eases this progress makes possible ( or competitive) the measurement of a quantity formerly available via computations only. One example is the detailed measurement of the electronic density of a molecule, and of the related molecular electrostatic potential. The determination of these two observables has been for many years a task feasible only by quantum-mechanical methods, now the progresses in the elaboration of diffraction technique measurements makes possible a direct determination. 

In the present work, we shall investigate the problem of the amount of correlation accounted for in the DF formalism by comparing the molecular electrostatic potentials (MEPs) and dipole moments of CO and N2O calculated by DF and ab initio methods. It is indeed well known that the calculated dipole moment rf these compounds is critically dependent on the level of theory implemented and, in particular, that introduction of correlation is essential for an accurate prediction [13,14]. As the MEP property reflects reliably the partial charges distribution on the atoms of the molecule, it is expected that the MEP will exhibit a similar dependence and that its gross features correlate with the changes in the value of dipole moment when switching from one level of theory to the other. Such a behavior has indeed been reported recently by Luque et al. [15], but their study is limited to the ab initio method and we found it worthwhile to extend it to the DF formalism. Finally, the proton affinity and the site of protonation of N2O, as calculated by both DF and ab initio methods, will be reported. 

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. 

Pullman, A. Pullman, B. Molecular electrostatic potential of nucleic acids. Q. Rev. Biophys. 1981, 14, 289-380. 

Politzer, P. and Murray, J.S. (1990) Chemical applications of molecular electrostatic potentials, Transactions ACA, 26, 23-39. 

Stewart, R.F. and Craven, B.M. (1993) Molecular electrostatic potentials from crystal diffraction The Neurotransmitter y -aminobutyric acid, Biophys. J., 65, 998-1005. 

Belvisi, L., Bonati, L., Bravi, G., Pitea, D., Scolastico, C. and Vulpetti, A. (1993) On the role of the molecular electrostatic potential in modelling the activity of non-peptide angiotensin II receptor antagonists, J. Mol. Struct. (Teochem.), 281, 237-252. 

In this category, among the molecular, electrostatic and magnetic interparticle bonds, interest is primarily centered on the van der Waals-type attractive forces that may predominate in the absence of liquid and solid bonds. The force of the van der Waals attraction between two spheres of equal size is (R4)... 

Tasi, G., and Palinkd,1. Using Molecular Electrostatic Potential Maps for Similarity Studies. 174, 45-72 (1995). 

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... 

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