Mulliken Electronegativity Research Articles

An extended form of the Evans–Polanyi equation: a simple empirical relationship for the prediction of activation energies for hydrogen-atom transfer reactions

An empirical approach has been used to devise a simple relationship [eqn. (B)] between the activation energy for an elementary hydrogen-atom transfer reaction (A) and ground state properties A˙+ H–B → A–H + B˙(A), Ea=Eof+αΔH°(1–d)+βΔχAB2+γ(sA+sB)(B) of the reactants and products. The role of polar effects, which operate in the transition state, is emphasised and described quantitatively in terms of the difference in Mulliken electronegativities (ΔχAB) of the radicals A˙ and B˙. Eqn. (B) reproduces the activation energies for 65 reactions, taken from the literature, within a standard error of ±2.0 kJ mol –1 and with a correlation coefficient of 0.988. Reactions of widely differing types are included and no distinction is made between gas-phase reactions and those which take place in non-polar solvents. Examples of hydrogen-atom transfer reactions which are not treated satisfactorily by eqn. (B) are discussed.

Multipole moment analysis for hydrides, fluorides, and lithium compounds of first‐ and second‐row elements

AbstractA method is presented that conserves all local dipole moments in a partitioning of overlap charge between pairs of atoms. The approximate conservation of quadrupole and higher‐moment components can be used as a criterion for the suitability of atomic basis sets. Ab initio calculations are presented for hydrides, fluorides, and lithium compounds of first‐ and second‐row elements in a systematic study of compounds and basis sets. The best suitable basis set for each series is determined by the criterion of best approximate conservation of quadrupole moment components. A linear relation between charge shifts and Mulliken electronegativity differences is established for diatomic molecules. © 1993 John Wiley & Sons, Inc.

A universal density criterion for correlating the radii and other properties of atoms and ions

On the basis of an improved Thomas-Fermi-Dirac (TFD)-type method, a characteristic radius r D is defined for a free atom or ion, where the electron density acquires the universal value of 0.008714. This value is obtained from the ratio of the Dirac exchange constant to the TF kinetic energy constant. Among vertical groups in the Periodic Table, r D calculated from near-Hartree-Fock densities shows striking linear relationships with the empirical covalent radius, the van der Waals radius, the Wigner-Seitz radius, the ionic radius, the first ionization potential, the electronegativity, the softness, the dipole polarizability and the London dispersion coefficient. The potential at r D due to the net charge inside a sphere of radius r d also varies linearly as Mulliken's electronegativity, among vertical groups. On the average, a sphere of radius r d contains more than 95% of the total electronic charge. The horizontal variations in r d among non-transition, transition, and inner transition atoms are sensitive to the changes in electronic configuration, identifying half-filled and completely filled Subshells and also reflecting the lanthanide contraction.

Electronegativity and hardness of molecular groups from the localized electronegativity group orbital (LEGO) and generalized exchange local spin density functional (LSD-GX) theories

Mulliken electronegativities and Orsky-Whitehead acid-base hardnesses were determined for selected non-quark and quark atoms. The ionization potentials and electron affinities were calculated from statistical total energies calculated using the self-interaction corrected generalized exchange local spin density functional theory with Vosko, Wilks and Nusair correlation energy (LSD-GX-VWN-SIC). There is good agreement with experiment for non-quark atoms; there is moderate agreement for quark atoms compared to quark atom data calculated by alternative methods. The valence state ionization potentials for the sp 3 and sppp valence states were calculated for selected non-quark and quark atoms using the LSD-GX and LSD-GX-VWN-SIC theories, and used to calculate the neutral, acid and base electronegativities and the Orsky-Whitehead acid-base hardnesses for molecular groups. The results show the expected behaviour for the sp 3 valence state for both non-quark and quark atoms and molecular groups. The hard-soft acid-base (HSAB) theory is discussed with respect to the trends observed in the data and is used to predict the correct behaviour in a representative hard-soft acid-base reaction.

Charge-dependent Hamiltonian for first- and second-row atomic properties

Charge-dependent parameters have been developed for hydrogen through argon that allow the calculation of average valence energies for a wide range of atomic charge. These parameters allow atoms in molecules to contract or expand with charge, emulating the capability of more complex multiple-ζ ab initio calculations while retaining the simplicity of a minimal basis formalism. In addition to promotion energies being reproduced, Mulliken electronegativities are also successfully reproduced, as are absolute hardness values

A sum rule for the vibrational intensities of substituted methanes

An electronegativity model for the calculation of gas-phase fundamental intensity sums of the halomethanes is proposed. The substituent effective charges are assumed to be linearly related to their Mulliken electronegativities and the carbon effective charges to their average substituent electronegativities. The model is particularly convenient for analyzing atomic contributions to the intensity sums.

Revised Mulliken electronegativities: II. Applications and limitations

This article is part two in a series. In this wok, some of the more important applications of Mulliken electronegativities to topics in chemical education are discussed, problems with the Mulliken system are identified, and recommendations are made for future research.

Revised Mulliken electronegativities: I. Calculation and conversion to Pauling units

Electronegativity is treated as a global atomic property that is determined by the valence state.

On the existence of absolute Pauling electronegativities

From a reappreciation of the recently proposed Parr—Pearson scheme on absolute electronegativity and hardness, it follows that electron affinities can be considered as absolute Pauling electronegativities. The fundamental difference between Pauling and Mulliken electronegativities is demonstrated. A quantumchemical framework of Hückel-type is developed wherein these electron affinities act as one-electron energies (diagonal matrix elements). This novel definition of absolute Pauling electronegativities is shown to be consistent with Pauling's original bond energy equation. The validity of the deductions made implies a possible new look at chemical exchange forces in terms of intra-atomic charge-invariance effects (atom—antiatom interactions).

Isomer shifts of the 6.2 keV nuclear transition of Ta-181 in sulvanite type ternary phases Cu 3TaX 4 (X=S,Se,Te)

The isomer shift of the 6.2 keV nuclear transition of Ta-181 in Cu 3TaTe 4 was determined by nuclear gamma resonance spectroscopy. The value obtained amounts to +55.95±0.06 mm/s relative to tantalum metal. The isomer shifts in the three isotypic compounds Cu 3TaX 4 are related linearly to the Mulliken electronegativities of the chalcogens X = S, Se, Te. A correlation between isomer shifts and the unit cell volumes is deduced for these compounds in good agreement with the experimental results.

Synthesis and 119Sn mössbauer spectroscopic studies of inorganic tin(IV) halide and mixed halide/pseudohalide complexes with n-donor ligands

A series of tin(IV) halide and tin(IV) halide isothiocyanate adducts of nitrogen-donor ligands, of general formulae, X nSn(NCS) 4−n·L 2, (n = 2−4), have been synthesized and studied by 119Sn Mössbauer spectroscopy. The complexes all show single Mössbauer resonances and their isomer shift values are found to be a linear function of the average Mulliken electronegativities of the halide/isothiocyanate ligands around the tin atom.

On the pauling electronegativity scales—II

From the analysis of the electrostatic potential near the core-valence boundary in an atom, it is shown that the Pauling electronegativity scale χ p is approximately given by the formula, ▪ where N v is the valence electron number and f( n) is some function of the periodic number in the periodic table. It is also shown in detail that the Pauling electronegativity scale is closely related to the Wang-Parr electronegativity scale which is determined as the negative of the chemical potential in density functional theory. Correlation between the Pauling and Mulliken electronegativities is briefly discussed.

Diffusion in phases with several components and sublattices

Alkali metal-based sorbents are potential for oxidized mercury (Hg2+) selective adsorption but show hardly effect to elemental mercury (Hg0) in flue gas. Density functional theory (DFT) was employed to investigate the Hg0 and HgCl2 adsorption mechanism over alkali metal-based sorbents, including calcium oxide (CaO), magnesium oxide (MgO), potassium chloride (KCl) and sodium chloride (NaCl). Hg0 was found to weakly interact with CaO (001), MgO (001), KCl (001) and NaCl (001) surfaces while HgCl2 was effectively adsorbed on top-O and top-Cl sites. Charge transfer and bond population were calculated to discuss the covalency and ionicity of HgCl2 bonding with the adsorption sites. The partial density of states (PDOS) analysis manifests that HgCl2 strongly interacts with surface sites through the orbital hybridizations between Hg and top O or Cl. Frontier molecular orbital (FMO) energy and Mulliken electronegativity are introduced as the quantitative criteria to evaluate the reactivity of mercury species and alkali metal-based sorbents. HgCl2 is identified as a Lewis acid and more reactive than Hg0. The Lewis basicity of the four alkali metal-based sorbents is predicted as the increasing order: NaCl < MgO < KCl < CaO, in consistence with the trend of HgCl2 adsorption energies.

Studies on 13C magnetic resonance spectroscopy. XVI. On the introduction of the entropy term .DELTA.S.DEG. for the elucidation of Ipso- and .ALPHA.-13C substituent-induced chemical shifts by an empirical approach.

^ C Substituent-induced chemical shifts (SCS) at the ipso and α positions of monosubstituted benzenes or methanes can be expressed by a linear combination of three kinds of empirical parameters, σi, σπ, and ΔS°. ΔS° represents the difference of the entropy (due to the substituent) between the standard entropy S°of the substituted compound and that of the parent one. The following results were obtained. SCSipso=63.9·σi-3.9·σπ+0.6ΔS°+-0.4·ΔS°-+3.8 (r=0.927, SD=4.9 ppm, n=13) SCSα=162.1·σi-10.1·σπ+1.2·ΔS°+-0.3·ΔS°-+2.3 (r=0.976, SD=4.9ppm, n=13) where + and - subscripts of ΔS° indicate electron-donating and -attracting groups, respectively. This treatment is also applicable for elucidation of the 13C SCS of analogous positions of many substituted aromatics and heteroaromatics, including ortho-disubstituted benzenes, and provides a reasonable and explicit chemical basis for the origin of the 13C SCSipso and SCSα. The same treatment also provides an explicit chemical basis for Mulliken's electronegativity scale and the steric substituent constant, Es.

On the Dependence of Total Energy on Occupation Numbers

AbstractAn equation is developed for describing the pairwise interactions of q electrons, when q is integer or non‐integer. This expression is compared with the usual equation. It is found to give lower total energies, different ionization and transition energies in the Slater Transition State theory, different values for the atomic energies calculated by the Hyper‐Hartree–Fock method, but numerically identical results for the Mulliken Electronegativity.

Possibilities of new materials for solar photovoltaic cells

The requirements for desirable technological properties of semiconductors for photovoltaic conversion are discussed and two criteria are suggested for the selection of materials that could guide the search towards low melting compounds made of cheap component elements: (1) the use of a deviation from ideality vs. energy gap diagram for the prediction of energy gaps from the knowledge of melting temperatures or viceversa; (2) the use of the Parthé-Goryunova-Mooser-Pearson criteria for compounds of which only their chemical formula is known but not their structure, in order to guess the structure and therefore be able to use the first criterion. For materials for Schottky devices a third criterion is necessary, derived by Nethercott that relates the Mulliken electronegativities of the component elements of a compound to its electron affinity. This can also be applied in the search of metallic alloys, semimetals or narrow band gap semiconductors that might replace the metal in a Schottky barrier. It is shown that a number of compounds exists which might meet these criteria.

A Mulliken electronegativity scale and the structural stability of simple compounds

A Mulliken electronegativity scale and the structural stability of simple compounds

A Mulliken electronegativity scale and the structural stability of simple compounds

A new electronegativity scale is derived, in the spirit of Mulliken's original scheme, in terms of neutral atom spectroscopic data. The effect of changing the atomic configuration for C from covalent ( sp 3) to metallic ( s 2 p 2) is considered. Structural stability maps are presented for non-octet non-transition metal compounds, and for two classes of transition metal-non-transition-metal compounds.

The relationship between the Mulliken electronegativities of the elements and the work functions of metals and nonmetals

The relationship between the Mulliken electronegativities of the elements and the work functions of metals has been investigated, and it has been found that these two are equal. This investigation has been extended to binary nonmetals using a relationship proposed by Nethercot with good success so that a general procedure for the experimental determination of Mulliken electronegativities for the elements has been established. In addition, values of valence state promotion energies and electron affinities for several elements have been calculated.

Vinyl polymerization. 93. Polar effects in radical polymerization of p‐substituted styrenes

AbstractThe radical polymerization of styrene and of the p‐substituted styrenes p‐methoxy‐, p‐methyl‐, p‐fluoro‐, p‐chloro‐, p‐bromo‐, and p‐cyanostyrene, was kinetically studied. The styrenes with more electron‐attracting substituents show a greater overall rate of polymerization. At 30,0°C., the individual rate constants of propagation (kp) and termination (kt) were determined by a rotating sector and by usual inhibitor method using diphenylpicrylhydrazyl (DPPH) or p‐benzoquinone. It was found that the following HAMMETT relationship is established in the homopolymerization of p‐substituted styrenes: where σ is the HAMMETT constant, and ρ′ is a reaction constant which was calculated as +0.6. This relation is interpreted from a participation of ionic structures in the transition state of the propagation reaction. For confirmation, MULLIKEN's electronegativity of the p‐substituted styrene and the p‐substituted benzyl radical was calculated by simple LCAO MO method. The relationship between the rate constants of termination, kt, and the σ‐values is expressed by two lines, crossing at p‐fluorostyrene which is at the maximum point. These two lines are explained by two ways; one is the diffusion controlled termination and the other is the recombination of the two polarized radical ends.