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Complexation Energies (complexation + energy)
Selected AbstractsDensity Functional Study of the Complexation Reaction of Sn(CH3)3X (X = F, Cl, Br and I) with Halide AnionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2003Frank De Proft Abstract The Lewis acid-base reaction between Sn(CH3)3X and Y, (with X, Y = F, Cl, Br and I) has been studied using quantum chemical calculations. Complexation energies were calculated at the Density Functional Theory (DFT) level and rationalized on the basis of a local application of the hard and soft acids and bases principle. It was observed that smaller differences in the local softness of the interacting sites in the Lewis acid and base correspond to stronger interactions. Moreover, the calculated sequences in complexation energies can be reproduced using equations containing chemical concepts introduced within the framework of conceptual density functional theory and rooted in the hard and soft acids and bases principle and referring only to the reactants. A method of treating the electronegativity and softness of the halide anions is presented based on a Taylor expansion of the electronegativity of the neutral halogens and the softness-polarizability proportionality. Experimental evidence for the calculated sequences was gathered from measured 117Sn chemical shifts and 1J (13C- 119/117Sn) coupling constant changes upon complexation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Amphiphilic Organic Ion Pairs in Solution: A Theoretical StudyCHEMPHYSCHEM, Issue 10 2007Vincent Pradines Dr. Abstract The macroscopic manifestation of hydrophobic interactions for amphiphilic organic ion pairs (tetraalkylammonium,anion) has been shown experimentally by measuring their association constants and their affinity with the organic phase. Beyond a certain size, there is a direct relation between association constants and chain lengths in tetraalkylammonium ions. We propose to cast a bridge between these results and geometrical properties considered at the level of a single ion pair by means of quantum chemistry calculations performed on model systems: trimethylalkylammonium,pentyl sulfate instead of tetraalkylammonium,dodecyl sulfate. Two limiting cases are considered: head-to-head configurations, which yield an optimal electrostatic interaction between polar heads, and parallel configurations with a balance between electrostatic and hydrophobic interactions. All properties (geometries, complexation energies, and atomic charges) were obtained at the MP2 level of calculation, with water described by a continuum model (CPCM). Dispersion forces link hydrocarbon chains of tetraalkylammonium ions and pentyl sulfate, thus yielding (for the largest ion pairs) parallel configurations favored with respect to head-to-head geometries by solute,solvent electrostatic interactions. Given the small experimental association energies, we probe the accuracy limit of the MP2 and CPCM methods. However, clear trends are obtained as a function of chain length, which agree with the experimental observations. The calculated monotonic stabilization of ion pairs when the hydrocarbon chain increases in length is discussed in terms of electrostatic interactions (between ions and between ion pairs and water), dispersion forces, and cavitation energies. [source] A Rearrangement of Azobenzene upon Interaction with an Aluminum(I) Monomer LAl {L = HC[(CMe)(NAr)]2, Ar = 2,6- iPr2C6H3}EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005Hongping Zhu Abstract Reaction of LAl (1) or [LAl{,2 -C2(SiMe3)2}] (2) {L = HC[(CMe)(NAr)]2, Ar = 2,6- iPr2C6H3} with azobenzene affords a five-membered ring compound [LAl{N(H)- o -C6H4N(Ph)}] (3). In the formation of 3 a three-membered intermediate [LAl(,2 -N2Ph2)] (A) is suggested by a [1 + 2] cycloaddition reaction; A is not stable and further rearranges to 3. DFT calculations on similar compounds with modified L' {L' = HC[(CMe)(NPh)]2} show that the complexation energy of the reaction of L'Al with azobenzene to form [L'Al(,2 -N2Ph2)] is about,39 kcal,mol,1, and the best estimate of the energy difference between [L'Al(,2 -N2Ph2)] and [L'Al{N(H)- o -C6H4N(Ph)}] is,76 kcal,mol,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] | ||||||||||