Electrophilicity Equalization Principle

A new electronic structure principle, viz., the principle of electrophilicity equalization is proposed. An analytical justification as well as a numerical support for the same is provided.Comment: 9 pages, 2 table

Aromatic Superhalogens

No organic molecules with electron affinities near or above those of halogens are known. We show for the first time that aromaticity rules can be used to design molecules with electron affinities far exceeding those of halogen atoms either by tailoring the ligands of cyclopentadienyl or by multiple benzo-annulations of cyclopentadienyl in conjunction with the substitution of CH groups with isoelectronic N atoms. Results based on density functional theory reveal that the electron affinities of some of these organic molecules can reach as high as 5.59 eV, thus opening the door to new class of superhalogens that contain neither a metal nor a halogen atom

Bonding, Reactivity and Aromaticity in Some Beryllocene Derivatives

Geometries of [X3−M−Y3]2−: X, M, Y = Be, Mg; [Cp−M−Y3]−: M, Y = Be, Mg and [Cp−M−Cp]; M = Be, Mg; Cp− = C5H5− are optimized at the B3LYP/6-311+G(d) level of theory and the frequencies are also calculated at the same level of theory. Interesting bonding, reactivity and aromaticity trends emerge as one keeps on changing Cp− units of beryllocene by the triangular aromatic dianions, X32− (X = Be, Mg) as well as by replacing the central Be by Mg. Similar substitution of Cp− by Al42− and the additional change in the number of electrons yield all – metal complexes devoid of the original square planar Al42− rings and with newly formed roughly rectangular aromatic rings. Atomic charges and Fukui functions lend additional insights into the local reactivity patterns of individual atomic centers

18-Electron rule inspired Zintl-like ions composed of all transition metals

Zintl phase compounds constitute a unique class of compounds composed of metal cations and covalently bonded multiply charged cluster anions. Potential applications of these materials in solution chemistry and thermoelectric materials have given rise to renewed interest in the search for new Zintl ions. Up to now these ions have been mostly composed of group 13, 14, and 15 post-transition metal elements and no Zintl ions composed of all transition metal elements are known. Using gradient corrected density functional theory we show that the 18-electron rule can be applied to design a new class of Zintl-like ions composed of all transition metal atoms. We demonstrate this possibility by using Ti@Au122 and Ni@Au6 2 di-anions as examples of Zintl-like ions. Predictive capability of our approach is demonstrated by showing that FeH6 4 in an already synthesized complex metal hydride, Mg2FeH6, is a Zintl-like ion, satisfying the 18-electron rule. We also show that novel Zintl phase compounds can be formed by using all transition metal Zintl-like ions as building blocks. For example, a two-dimensional periodic structure of Na2[Ti@Au12] is semiconducting and nonmagnetic while a one-dimensional periodic structure of Mg[Ti@Au12] is metallic and ferromagnetic. Our results open the door to the design and synthesis of a new class of Zintl-like ions and compounds with potential for applications.

Pressure-Induced Magnetic Crossover Driven by Hydrogen Bonding in CuF2(H2O)2(3-chloropyridine)

Hydrogen bonding plays a foundational role in the life, earth, and chemical sciences, with its richness and strength depending on the situation. In molecular materials, these interactions determine assembly mechanisms, control superconductivity, and even permit magnetic exchange. In spite of its long-standing importance, exquisite control of hydrogen bonding in molecule-based magnets has only been realized in limited form and remains as one of the major challenges. Here, we report the discovery that pressure can tune the dimensionality of hydrogen bonding networks in CuF2(H2O)2(3-chloropyridine) to induce magnetic switching. Specifically, we reveal how the development of exchange pathways under compression combined with an enhanced ab-plane hydrogen bonding network yields a three dimensional superexchange web between copper centers that triggers a reversible magnetic crossover. Similar pressure- and strain-driven crossover mechanisms involving coordinated motion of hydrogen bond networks may play out in other quantum magnets

Stability, reactivity, and aromaticity of compounds of a multivalent superatom

In this article, we analyze the stability, reactivity, and possible aromatic behavior of two recently reported clusters (Reveles, J. U.; Khanna, S. N.; Roach, P. J.; Castleman, A. W., Jr. Proc. Natl. Acad. Sci. 2006, 103, 18405), viz., Al7C- and Al7O- in the light of the principles of the maximum hardness and minimum electrophilicity as well as the nucleus-independent chemical shift values. Stability of these clusters in the context of addition/removal of an electron or an Al atom is now clearly understood

Potential use of some metal clusters as hydrogen storage materials-a conceptual DFT approach

Structure, stability and reactivity of several metal clusters with or without hydrogen doping were studied using standard ab initio and density functional theory (DFT) calculations. Conceptual DFT-based reactivity descriptors and the associated electronic structure principles lend additional support towards understanding the stability of metal clusters upon hydrogen doping. Related aromaticity was analyzed through nucleus-independent chemical shift values. Site selectivity towards electrophilic and nucleophilic attacks were analyzed in terms of the corresponding local reactivity descriptors. Most of the metal clusters have the capacity to trap hydrogen molecules