Molecular orbital fields

Waller et al. (237) performed a CoMFA study to analyze the metabolic rates of CYP2E1 in rodents as intrinsic clearance of a 12 chlorinated volatile organic compounds (VOCs). After superimposition, the steric and electrostatic field interaction energies, the HINT (/jydropathic interactions) energy (238), and molecular orbital field were calculated in addition to clogP. The best model... 

Molecular orbital fields are descriptors particularly useful when an ionic or charge transfer reaction is part of the ligand-receptor interaction in this case, electrostatic fields are not able to fully represent the electronic characteristics of molecules. 

In order to calculate a molecular orbital field, semiempirical single-point calculations are performed on the molecule optimized geometry and the electron density at each grid point in the region of the selected orbital is determined. 

Waller, C.L. and Marshall, G.R. (1993). Three Dimensional Quantitative Structure-Activity Relationship of Angiotesin Converting Enzyme and Thermolysin Inhibitors. 2. A Comparison of CoMFA Models Incorporating Molecular Orbital Fields and Desolvation Free Energies Based on Active Analog and Complementary Receptor Field Alignment Rules. JMeeLChem., 36,2390-2403. 

Waller CL, Marshall GR (1993) Three-dimensional quantitative structure-activity relationship of angiotesin-converting enzyme and thermolysin inhibitors. II. A comparison of CoMFA models incorporating molecular orbital fields and desolvation free energies based on active-analog and complementary-receptor-field alignment rules. J Med Chem 36(16) 2390-2403... 

HOMO fields have been shown to be beneficial for the refinement of 3D-QSAR models for data sets such as the angiotensin converting enzyme (ACE) inhibitors. HOMO fields appear to describe the interaction between the ionized ligand and the metal ion in the molecular binding domain. More recently, molecular orbital fields have been used in the construction of 3D-QSAR models for molecular reactivity end points (e.g., metabolic rate constants). ... 

Pisani C 1978 Approach to the embedding problem in chemisorption in a self-consistent-field-molecular-orbital formalism Phys. Rev. B 17 3143... 

For Iran sition metals th c splittin g of th c d orbitals in a ligand field is most readily done using HHT. In all other sem i-ctn pirical meth -ods, the orbital energies depend on the electron occupation. HyperCh em s m oiccii lar orbital calcii latiori s give orbital cri ergy spacings that differ from simple crystal field theory prediction s. The total molecular wavcfunction is an antisymmetrized product of the occupied molecular orbitals. The virtual set of orbitals arc the residue of SCT calculations, in that they are deemed least suitable to describe the molecular wavefunction, ... 

M Li rrell, J. N. IIurgel, A. J. Sem i empirical Seif ron.sisienf field. Molecular Orbital Theory of MoleculesWes In Icrscieri ce. New York. l J7I. 

The single Slater determinant wavefunction (properly spin and symmetry adapted) is the starting point of the most common mean field potential. It is also the origin of the molecular orbital concept. 

J. N. Murrell, A. J. Harget, Semi-empirical self-consistent-field molecular orbital theory of molecules John Wiley Sons, New York (1972). 

A configuration interaction calculation uses molecular orbitals that have been optimized typically with a Hartree-Fock (FIF) calculation. Generalized valence bond (GVB) and multi-configuration self-consistent field (MCSCF) calculations can also be used as a starting point for a configuration interaction calculation. 

The second step determines the LCAO coefficients by standard methods for matrix diagonalization. In an Extended Hiickel calculation, this results in molecular orbital coefficients and orbital energies. Ab initio and NDO calculations repeat these two steps iteratively because, in addition to the integrals over atomic orbitals, the elements of the energy matrix depend upon the coefficients of the occupied orbitals. HyperChem ends the iterations when the coefficients or the computed energy no longer change the solution is then self-consistent. The method is known as Self-Consistent Field (SCF) calculation. 

Crystal field and ligand field molecular orbitals... 

Figure 7.41 Perturbation of crystal field molecular orbitals (MOs) by ligand MOs...

Replacing one carbon atom of naphthalene with an a2omethene linkage creates the isomeric heterocycles 1- and 2-a2anaphthalene. Better known by their trivial names quinoline [91-22-5] (1) and isoquinoline [119-65-3] (2), these compounds have been the subject of extensive investigation since their extraction from coal tar in the nineteenth century. The variety of studies cover fields as diverse as molecular orbital theory and corrosion prevention. There is also a vast patent Hterature. The best assurance of continuing interest is the frequency with which quinoline and isoquinoline stmctures occur in alkaloids (qv) and pharmaceuticals (qv), for example, quinine [130-95-0] and morphine [57-27-2] (see Alkaloids). 

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