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Journal of Thermal Analysis and Calorimetry
Authors: Sahra C. Lemos, Silmar J. S. Franchi, Adelino V. G. Netto, Antonio E. Mauro, Oswaldo Treu-Filho, Regina C. G. Frem, Eduardo Tonon de Almeida, and Cláudia Torres

synthesis, characterization, DFT calculations, and thermal studies on compounds 1 – 4 (Scheme 1 ) by means of thermogravimetry (TG) and differential thermal analysis (DTA). Scheme 1 Structural representation of the

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with nucleus independent chemical shift (NICS). Density functional theory (DFT) has been found to be successful for determining activation barriers, molecular energies, molecular geometries, electronic and magnetic properties [ 5 – 11 ]. Also, NBO

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Journal of Thermal Analysis and Calorimetry
Authors: Hermi F. Brito, Jukka Hassinen, Jorma Hölsä, Högne Jungner, Taneli Laamanen, Mika Lastusaari, Marja Malkamäki, Janne Niittykoski, Pavel Novák, and Lucas C. V. Rodrigues

combination of experimental TL data and theoretical DFT (Density Fuctional Theory) calculations. The aim was to gain more information on which kind species act as the energy reservoirs in these materials. Experimental The

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interaction energies of non-polar group effect on inclusion for α-CD and aliphatic nitriles in the gas phase and aqueous solution, DFT calculations were performed. Experimental Materials Aliphatic nitriles (H

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Abstract  

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $${\text{Cs}}^{ + } \left( {\text{aq}} \right) + {\text{A}}^{ - } \left( {\text{aq}} \right) + {\mathbf{1}}\left( {\text{nb}} \right)\underset {} \rightleftharpoons {\mathbf{1}}\cdot{\text{Cs}}^{ + } \left( {\text{nb}} \right) + {\text{A}}^{ - } \left( {\text{nb}} \right)$$ \end{document}
taking place in the two-phase water-nitrobenzene system (A = picrate, 1 = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K ex (1·Cs+, A) = 4.4 ± 0.1. Further, the stability constant of the 1·Cs+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Cs+) = 6.3 ± 0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting cationic complex species 1·Cs+ was solved.
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Abstract  

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs+(aq) + A(aq) + 1(nb) ⇆ 1·Cs+(nb) + A (nb) taking part in the two-phase water–nitrobenzene system (A = picrate, 1 = hexaarylbenzene-based receptor; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K ex (1·Cs+, A) = 2.8 ± 0.1. Further, the stability constant of the hexaarylbenzene-based receptor·Cs+ complex (abbrev. 1·Cs+) in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β nb (1·Cs+) = 4.7 ± 0.1. By using quantum mechanical DFT calculations, the most probable structure of the 1·Cs+ complex species was solved. In this complex having C 3 symmetry, the cation Cs+ synergistically interacts with the polar ethereal oxygen fence and with the central hydrophobic benzene bottom via cation–π interaction. Finally, the calculated binding energy of the resulting complex 1·Cs+ is −220.0 kJ/mol, confirming relatively high stability of the considered cationic complex species.

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Ziegler-Natta catalytic systems

Calorimetric and DFT study on TiCl4-Lewis base interactions

Journal of Thermal Analysis and Calorimetry
Authors: L. Cavallo, J. Ducéré, Rosalisa Fedele, A. Melchior, Maria Mimmi, G. Morini, F. Piemontesi, and Marilena Tolazzi

Abstract  

A calorimetric investigation on the reactions of TiCl4 with phthalates in 1,1,2,2-tetrachloroethane (TCE) is presented in order to better understand the complex interactions present in Ziegler-Natta catalytic systems. The Lewis bases diethyl isophthalate (L1), diethyl terephthalate (L2) and the ortho-isomer diethylphthalate (L3), have been chosen to study how the substituent positions could influence the energy and the stoichiometry of the complexation reactions. FTIR spectroscopy was used to obtain information on the coordination mode of the ligands and diffusion measurements by NMR was carried out to verify the presence of oligo-or polymeric species. Experimental results were compared with theoretical calculations based on Density Functional Theory (DFT).

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Computational chemistry Density functional theory (DFT) calculations were carried out using the Amsterdam density functional (ADF) 2009 programme [ 27 – 29 ] with the generalized gradient approximation functional PW91 (Perdew–Wang, 1991) [ 30 ]. The

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calculations indicate a strong negative effect of Pb atoms on the strength of the C 2 H 2 adsorption on the alloy. Very recently, a periodic slab density functional theory (DFT) study has been reported by García-Mota et al. [ 42 ] and it has provided the

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isolated and deposited on a carbon support. The interaction between H 2 and the dimers is investigated by means of a simple theoretical approach based on density functional theory (DFT) combined with relatively modest basis sets. Our work addresses the

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