Pearson′s chemical hardness, heterolytic dissociative version of Pauling′s bond-energy equation and a novel approach towards understanding Pearson′s hard–soft acid–base principle

Datta, Dipankar; Singh, Shweta

doi:10.1039/dt9910001541

Cited by 20 publications

(16 citation statements)

References 19 publications

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“…As the number of molecules on both sides of reaction (6) in the gas phase are equal, the entropy factor is expected to be similar for all solvents. 9 Since the cathodic peak for couple (5) is only observed in CH 2 Cl 2 , we have investigated the possible correlation between ÀDH 0 and E pa , assuming that DE p in all solvents remains comparable to that observed in CH 2 Cl 2 . Fig.…”

Section: Resultsmentioning

confidence: 99%

The electrooxidation of the tetraphenylborate ion revisited

et al. 2002

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Section: Resultsmentioning

confidence: 99%

The electrooxidation of the tetraphenylborate ion revisited

et al. 2002

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“…The HSAB concept has been successful in predicting reactivity preferences in many systems since its inception. 24-32…”

Section: Introductionmentioning

confidence: 99%

Utility of the Hard/Soft Acid−Base Principle via the Fukui Function in Biological Systems

Faver

Merz

2010

J. Chem. Theory Comput.

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The hard/soft acid-base principle has long been known to be an excellent predictor of chemical reactivity. The Fukui function, a reactivity descriptor from conceptual density functional theory, has been shown to be related to the local softness of a system. The usefulness of the Fukui function is explored and demonstrated herein for three common biological problems: ligand docking, active site detection, and protein folding. In each type of study, a scoring function is developed based on the local HSAB principle using atomic Fukui indices. Even with necessary approximations for its use in large systems, the Fukui function remains a useful descriptor for predicting chemical reactivity and understanding chemical systems.

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“…Equation 8 defines the global hardness of an isolated chemical species; , moreover, it is not applicable experimentally to the free monovalent monoatomic anions since the A values of such anions are not accessible in practice . The point is that eq 8 cannot be used as such to characterize the hardness of an ion in a molecule. , From our earlier works , it follows that can be a measure of the gas-phase hardness of an ion in a molecule. Our values (Table ) give rise to the following hardness orders (in gas phase) for the various closed shell monovalent ions studied here: Li + > Na + > K + > Rb + > Cs + and F - ≈ H - > Cl - > Br - > I - .…”

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confidence: 99%

“…Not many scales for hardness of an ion in a molecule are at present available. Elsewhere we have tried to develop one by thermochemical means − in the spirit of Pauling's thermochemical scale for electronegativity. , According to our thermochemical scale for the gas-phase hardness of an ion in a molecule, , the pertinent trends are Li + > Na + > K + > Rb + ≈ Cs + and H - > F - > Cl - > Br - > I - . Thus the two gas-phase hardness series generated by here are more or less in line with those expected chemically.…”

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Polarizability of an Ion in a Molecule. Applications of Rittner's Model to Alkali Halides and Hydrides Revisited

Hati

Datta

1996

J. Phys. Chem.

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An attempt is made to estimate the polarizability of an ion in an ionic diatomic molecule. The method is applied to alkali halide and hydride diatoms. In this connection, the applicability of Rittner's model to these test molecules is examined critically. A new phenomenological form of the repulsive part of Rittner's model is suggested. It is argued that the polarizability of an ion can be used as an index of the gas-phase chemical hardness of an ion in a molecule.Determination of the static electric dipole polarizability (hereinafter referred to simply as polarizability) R of an ion in a molecule is an old and important problem. It was realized long ago that R of an ion in a molecule is not the same as that in the free state. In 1934 Fajans 1 introduced a principle that states that R is diminished in the field of positive charge and increased in the field of negative charge. This statement was theoretically quantified later by Ruffa in 1963. 2 In the past there have been a number of attempts to estimate the R of an ion in a molecule. For a recent brief review on these efforts, see ref 3. Coker has found that in alkali halide crystals polarizability of an anion decreases while that of a cation increases. 4 Coker has also tried to find a relation between the R value of a free ion and that of the ion in a crystal. Here we are not interested in finding the R of an ion in a crystal lattice but that in an isolated molecule.A possible way of checking whether the R of an ion in a molecule has been estimated correctly is to work out Rittner's model 5 for a diatomic molecule AB in detail. In 1951, to explain bonding in specifically the alkali halide diatomics and to estimate their various spectroscopic constants theoretically, Rittner developed a model where an AB molecule is described as a cation-anion pair (polarizable charged spheres) held together by electrostatic attraction but prevented from collapse by a repulsive potential. In this model, the dipole moment µ and the ionic bond dissociation energy W are given by eqs 1 and 2, respectively. In eq 2 C is the van der Waals constant, φ(r) is the repulsive energy resulting from the overlap of the electron clouds of the two ions A + and B -, the last term represents the zero-point energy, and the superscripts + and -designate cation and anion, respectively. Using the derivatives of W with respect to r (of various orders) and some standard relations, 3,6 one can calculate the rotational-vibrational coupling constant (R e ), vibrational anharmonicity constant (ω e x e ), and other higher order spectroscopic constants, γ e and e (these notations are standard as used by Huber and Herzberg 7 ). This model, which because of its nature is likely to hold in rather ionic diatomics, has been examined by many workers in the past using mainly the alkali halide diatoms as the testing grounds 3,6,8-12 (in only one study 3 have the hydrides of the alkali metals been considered). As a general result, a simplification of Rittner's model by omitting the product terms R + R -, which arise ...

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Pearson′s chemical hardness, heterolytic dissociative version of Pauling′s bond-energy equation and a novel approach towards understanding Pearson′s hard–soft acid–base principle

Cited by 20 publications

References 19 publications

The electrooxidation of the tetraphenylborate ion revisited

The electrooxidation of the tetraphenylborate ion revisited

Utility of the Hard/Soft Acid−Base Principle via the Fukui Function in Biological Systems

Polarizability of an Ion in a Molecule. Applications of Rittner's Model to Alkali Halides and Hydrides Revisited

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