Academic literature on the topic 'Molecular Electrostatic Potential (MEP)'

Objective: Optimized molecular structures have been investigated by DFT/B3LYP method with 6-31G (d,p) basis set. Stability of Benzo and anthraquinodimethane derivatives 1-4, hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond has been analyzed by using natural bond orbital (NBO) analysis. Electronic structures were discussed and the relocation of the electron density was determined. Molecular electrostatic potential (MEP), local density functional descriptors has been studied. Nonlinear optical (NLO) properties were also investigated. In addition, frontier molecular orbitals analyses have been performed from the optimized geometries. An ionization potential (I), electron affinity (A), electrophilicity index (ω), chemical potential (µ), electronegativity (χ), hardness (η), and softness (S), have been investigated. All the above calculations are made by the method mentioned above.Methods: The most stable optimized geometries obtained from DFT/B3LYP method with 6-31G(d,p) basis set were investigated for the study of molecular structures, nonlinear properties, natural bond orbital (NBO), molecular electrostatic potential (MEP) and frontier molecular orbital of Benzo and anthraquinodimethane derivatives.Results: Reactive sites of electrophilic and nucleophilic attacks for the investigated molecule were predicted using MEP at the B3LYP/6-31G(d,p). Compound 4 possesses higher electronegativity value than all compounds so; it is the best electron acceptor; the more reactive sites for electrophilic attacks are shown in compounds 1 and 4, for nucleophilic attacks are indicated in compounds 2 and 3 and the more reactive sites in radical attacks are detected in compounds 2 and 4.Conclusions: Compound 1 is softest, best electron donor and more reactive than all compounds. The calculated first order hyperpolarizability was found much lesser than reported in literature for urea.

The quantum chemical calculations of organic compounds viz. (E)-1-(2,6-bis(4-chlorophenyl)-3-ethylpiperidine-4-ylidene)-2-phenyl-hydrazine (3ECl), (E)-1-(2,6-bis(4-chlorophenyl)-3-methylpiperidine-4-ylidene)-2-phenylhydrazine (3MCl) and (E)-1-(2,6-bis(4-chloro-phenyl)-3,5-dimethylpiperidine-4-ylidene)-2-phenylhydrazine (3,5-DMCl) have been performed by density functional theory (DFT) using B3LYP method with 6-311G (d,p) basis set. The electronic properties such as Frontier orbital and band gap energies have been calculated using DFT. Global reactivity descriptor has been computed to predict chemical stability and reactivity of the molecule. The chemical reactivity sites of compounds were predicted by mapping molecular electrostatic potential (MEP) surface over optimized geometries and comparing these with MEP map generated over crystal structures. The charge distribution of molecules predict by using Mulliken atomic charges. The non-linear optical property was predicted and interpreted the dipole moment (μ), polarizability (α) and hyperpolarizability (β) by using density functional theory.

To study the reactivity of arylsulfonyl halides, the molecular electrostatic potential (MEP) was considered for the first time as a descriptor. The reaction of hydrolysis of aromatic sulfonyl halides in the medium of mixed acetone-water solvents (according to the literature data of rate constants) was used as a model. The calculation of the structural parameters of the molecules of substituted arylsulfonyl halides was carried out using the ADF2014 software package at the level of the DFT/M06/6-311+G* (PCM) theory. It was found that the magnitude of the MEP on the sulfonyl sulfur atom is very sensitive to changes in the structure of substrates, which makes it possible to determine the change in the ratio between the rate of nucleophilic attack and anionoid abstraction of the leaving group. In particular, using the example of the hydrolysis reaction of substituted thiophenesulfonyl chlorides, it was shown that the acceleration of the reaction is observed with an increase in the donor properties of the substituents and the associated increase in the negative MEP value on the sulfonyl sulfur atom. The antibate character of the dependence of the hydrolysis constant values on the IEP value indicates that not the nucleophilic attack is the rate determining in the interaction of thiophene sulfonyl chlorides and the hydroxyl anion in this sample, but the abstraction of the chloride anion. This reaction has an unstable mechanism, when the ratio between the degree of S-nucleophile bond formation and S-halogen bond cleavage changes. This makes it possible to use MEP as a descriptor of reactivity in the hydrolysis of aryl sulfonyl halides and to elucidate the details of changes in the structure of transition states during the implementation of mechanisms other than pure SN2 mechanism.

Different characters of molecular electrostatic potential (MEP) in the ground and excited states of chalcogenides are responsible for changes in conformer stability of T-shape and stacked non-bonded chalcogenide–benzene complexes upon electronic excitation.