Heterotrimetallic compounds containing Mo-M-Li [M = K, Rb and Cs] clusters : synthesis, structure, bonding, aromaticity and theoretical investigations of Li₂M₂ [M = K and Rb] and Cs₄ rings

A new polydentate fac-trioxo molybdenum complex, [MoO3L]3− {LH3 = nitrilotriacetic acid}, has been synthesized by the reaction of lithium molybdate with iminodiacetic acid. The trinegative complex anion coordinates the alkali metal cations, K+, Rb+ or Cs+. The potassium, rubidium and cesium complexes, [Li{K(H2O)2}MoO3L]n (1), [Li{Rb(H2O)2}MoO3L]n (2) and [Cs{Li(H2O)}2MoO3L]n (3), form heterotrimetallic coordination chains, containing planar rings of Li2M2 (M = K or Rb) and Cs4. Theoretical investigations on these rings were carried out using NICS calculations and ab initio ring current maps, revealing aromaticity to be of limited significance

Conceptual aspects of electron densities and density functionals

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The maximum hardness principle implies the hard/soft acid/base rule

A recent paper [ P. W. Ayers, J. Chem. Phys122, 141102 (2005) ] considered the hard/soft acid/base exchange reaction, showing that the products associated with the hard/soft acid/base rule (in which the hard acid and hard base are bound, as are the soft acid and soft base) have lower energy than the alternative (in which the hard acid and soft base would have been bound and similarly the soft acid and hard base). Here we show that the maximum hardness principle also predicts this result. Unlike the previous derivation, we do not need to make any assumptions about the relative strength of the acids and bases

Hydrogen storage: An overview with current insights based on a conceptual DFT approach

226-244Importance of various conceptual density functional theory based reactivity descriptors and nucleus independent chemical shift in analyzing the hydrogen adsorption potential of a wide variety of systems is reviewed. The charges on the different atomic sites in a molecule also play a crucial role in this regard

Does confinement alter the ionization energy and electron affinity of atoms?

Confinement causes drastic changes in bonding, reactivity and dynamics. Alkali metal atoms are excellent reducing agents due to their low ionization energies. On the other hand, high electron affinity values allow the halogen atoms to behave as powerful oxidizing agents. In this article, we have shown that those properties get changed in a confined environment created by two fullerenes differing in size

Exploring the Nature of Silicon-Noble Gas Bonds in H3SiNgNSi and HSiNgNSi Compounds (Ng = Xe, Rn)

Ab initio and density functional theory-based computations are performed to investigate the structure and stability of H3SiNgNSi and HSiNgNSi compounds (Ng = Xe, Rn). They are thermochemically unstable with respect to the dissociation channel producing Ng and H3SiNSi or HSiNSi. However, they are kinetically stable with respect to this dissociation channel having activation free energy barriers of 19.3 and 23.3 kcal/mol for H3SiXeNSi and H3SiRnNSi, respectively, and 9.2 and 12.8 kcal/mol for HSiXeNSi and HSiRnNSi, respectively. The rest of the possible dissociation channels are endergonic in nature at room temperature for Rn analogues. However, one three-body dissociation channel for H3SiXeNSi and one two-body and one three-body dissociation channels for HSiXeNSi are slightly exergonic in nature at room temperature. They become endergonic at slightly lower temperature. The nature of bonding between Ng and Si/N is analyzed by natural bond order, electron density and energy decomposition analyses. Natural population analysis indicates that they could be best represented as (H3SiNg)+(NSi)− and (HSiNg)+(NSi)−. Energy decomposition analysis further reveals that the contribution from the orbital term (ΔEorb) is dominant (ca. 67%–75%) towards the total attraction energy associated with the Si-Ng bond, whereas the electrostatic term (ΔEelstat) contributes the maximum (ca. 66%–68%) for the same in the Ng–N bond, implying the covalent nature of the former bond and the ionic nature of the latter