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Geometries of several all-metal clusters with Zn32− as the base are optimized within a B3LYP/6-311+G(d) level of theory. It is analyzed that the stability, bonding, reactivity and aromaticity patterns of such clusters often change drastically in the presence of counter cations like Li+, Na+ or K+ and/or through the substitution of Zn32− units by Be5− or C5H5− rings.

Changes in the bonding, aromaticity and reactivity behavior associated with the following reaction cycle including all the intermediate steps are studied at the B3LYP/6-311+G(d) level of theory: Various sandwich-like complexes studied here may be synthesized and used for different purposes such as catalysis and molecular electronics.

Some representative chemical reactions and all-metal aromatic/antiaromatic compounds are studied ab initio in order to understand the efficacy of the multicenter indices in providing insights into the associated bonding, reactivity and aromaticity. It is observed that the said indices serve the purpose in most cases.

We present a systematic density functional theory study of the global and local reactivity patterns of [n]paracyclophanes. Maximum hardness principle (MHP) and minimum electrophilicity principle (MEP) are obeyed in these strained molecules. Linear relationships among strain energy, electrophilicity, aromatic stabilization energy and chemical hardness are established. The Fukui function (FF) values at the carbon atoms of the benzene ring of [n]paracyclophanes are critically analyzed. The presence of weak C-H...π interactions is evident from the AIM topographical analysis.

In this article, a philicity based site activation model for the Markovnikov regioselectivity rule is proposed. Electrophilic addition of HCl to a series of asymmetric alkenes is studied to demonstrate the efficacy of this model.

Density functional theory and ab initio molecular orbital calculations have been carried out in order to get insights into the structure, chemical reactivity and property information for the series of chloroanisoles. Descriptors such as energy, hardness, chemical potential, electrophilicity index and polarizability provide vital information about the global reactivity of chloroanisoles. Further, we utilized our recently proposed multiphilic descriptor defined as the difference between nucleophilic and electrophilic condensed philicity functions to understand the local reactivity/site selectivity on the series of chloroanisoles. Also, structure-property relationship in chloroanisoles shows the importance of the electrophilicity index in the property prediction.

The mechanism of intermolecular exchange of methyl and ethyl groups for chlorine in CH 3 SnCl 3 and C 2 H 5 SnCl 3 , respectively, has been probed through semiempirical (PM3) and density functional theory (B3PW91 and B3LYP) calculations. The reaction is explained by a mechanism involving the formation of the transition state comprising bridging alkyl and chloro groups. The PM3 calculated activation energies are 37.5 and 36.4 kcal mol -1 while the B3LYP/LANL2DZ calculated activation energies are 50.4 and 41.3 kcal mol -1 for the methyl and ethyl analogues, respectively. The rate constants calculated at the DFT level are in close agreement with the corresponding experimental values.

The charge transfer and joint hardness between benzidine, 3,3′-dimethoxybenzidine, 3,3′-dichlorobenzidine, 2,2′,5,5′-tetrachlorobiphenyl, 3,3′,4,4′,5,-pentachlorobiphenyl and dibenzofuran with nucleic acid bases such as adenine, thymine, guanine, cytosine, uracil, and base pairs like GCWC and ATH are investigated. It has been shown that benzidines act as electron donors whereas polychlorinated biphenyls and dibenzofuran act as electron acceptors during their interaction with biomolecular environments. Further, experimental biological activities (pIC 50 ) of polychlorinated dibenzofurans (PCDF) are correlated with their corresponding activity (pIC 50 values) calculated using the electrophilicity index and the local electrophilic power through regression analysis from different population analysis schemes like MPA, NPA and HPA. A good correlation is obtained showing the significance of the selected descriptors in quantitative structure toxicity prediction.

Cracking of n-heptane in HZSM-5 zeolite is studied through generalized gradient approximation mediated single point calculations at the BLYP-DZVP level on the extremal points of a corresponding quantum molecular dynamics simulation carried out at 800 K using the same level of theory. The global reactivity descriptors like electronegativity, hardness and electrophilicity are important in understanding the reaction mechanism in terms of the stabilities and reactivities of various species involved. Different centers become reactive towards electrophilic and nucleophilic attacks during the process of hydrocarbon cleavage and local reactivity descriptors adequately take care of that.

The toxicity of 33′44′55′-hexa chlorobiphenyl (HCBP), a non-ortho substituted polychlorinated biphenyl (PCB) is analyzed using the rotational energy barrier as well as some conceptual density functional theory (DFT) based global and local reactivity descriptors. The flexibility of the molecule is evident from the low value of rotational barrier height. The profiles of global reactivity descriptors and relative energy clearly demonstrate the overall toxic nature whereas the local descriptors provide information about the probable reactive sites of HCBP. The partial charge transfer during the interaction between HCBP and DNA bases/selected base pairs is also computed using Parr's formula. The flexibility and the electron accepting nature of HCBP are shown to be the dominant factors of its toxicity.

Variation of global reactivity descriptors along the two different pathways for formaldehyde decomposition has been investigated in order to analyze the validity of various electronic structure principles of density functional theory. Calculated energetics and geometrical parameters are in good agreement with the previous investigations. The hardness and electrophilicity are, respectively, found to be a pointer of the most stable and the most reactive identity in most cases. Profiles of these quantities, as a function of the reaction coordinates narrate the dependability of the descriptors. The difference in the global reactivity descriptors between a symmetric reaction and a non-symmetrical reaction along the reaction coordinate in the same decomposition pathway has also been analyzed. Our investigation provides useful exploratory guidelines towards the foundation of chemical reactivity descriptors.

A quantum fluid density functional approach is adopted in monitoring the dynamics of various global and local reactivity parameters of a helium atom in a two-state equiensemble, having an interaction with an external laser field as well as an incoming proton. The effect of an increase in the excited-state contribution in a two-state ensemble is more pronounced in global reactivity parameters than the local ones. Global reactivity indices are found to be more sensitive to the external perturbation, for the whole time-dependent process, than the local indices. Most of the local quantities show drastic changes only at the beginning of the processes. In the atom–field interaction problem, electronegativity, polarizability and entropy oscillate with the field and hardness attains a steady value after the initial transients die out. The ion–atom collision process can be divided into three distinct regimes in terms of the time-dependent electronegativity profile. In the encounter regime, hardness and entropy maximize and polarizability minimizes. Dynamical variants of the principles of maximum hardness, maximum entropy and minimum polarizability are shown to be operative.

The soft atoms and molecules are highly polarizable and magnetizable. An acid and a base of similar magnetizability values are expected to have stronger interactions than those with very different magnetizability values. The atomic shell structure may be considered to be a consequence of a minimum magnetizability principle.

A quadratic Euler-Lagrange equation has been solved self-consistently for defining two types of radii for atoms which match closely with experimental covalent radii. The calculated radii values are either better than or comparable to any hitherto known calculated radii values. Excellent correlations have been observed between these radii values and other physical properties like softness, ionisation potential, electronegativity etc. in the vertical groups of the periodic table and the trends are found to match with that predicted by experimental covalent radii.

The dissociation reaction, H 3 N · HF → H 3 N + HF and the proton-transfer reaction (F-H · Cl) − → (F· H-Cl) − have been studied at the HF//6-31G ∗∗ level in order to understand the progress of these reactions in terms of global and local reactivity parameters. Both the reactions are found to obey the maximum hardness principle. The potential energy curve for the proton transfer reaction passes through a transition state wherein the hardness is at a minimum. In this reaction bond index profiles of the bonds being broken and formed intersect at the point corresponding to the maximum in the potential energy curve. Condensed Fukui functions have been calculated at different stages of dissociation of H 3 N · HF. Variation of reactivity of a particular site towards electrophilic, nucleophilic or radical attack is properly reflected in these values.

The group electronegativities of several molecules were calculated using different basis sets and population analysis schemes. It was observed that satisfactory results are obtained using the 6-31G∗ basis set and the Mulliken population analysis scheme. The transferability of the group electronegativities was examined by calculating their values for a number of HG and LiG molecules, where G stands for the group.

Aromaticity indices originating from the principles of minimum energy and polarizability and maximum hardness are used in analyzing the behavior of all-metal aromatic ( Al 4 2 − ) and antiaromatic ( Al 4 4 − ) systems.