Correction to “Grand-Reaction Method for Simulations of Ionization Equilibria Coupled to Ion Partitioning” (original) (raw)
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To cite this article: Molecular Simulation (2013): A theoretical study of the conformational preference of alkyl-and arylsubstituted pyrogallol arenes and evidence of the accumulation of negative electrostatic potential within the cavity of their rccc conformers, Molecular Simulation, We report a theoretical study of the structural and electronic properties of the rccc and rctt conformers of several pyrogallol[4]arenes, R-Pyg[4]arenes (i.e. R ¼ fluoroethyl, methyl, t-butyl, phenyl, tolyl and p-fluorophenyl) carried out by employing the HF-DFT hybrid B3LYP functional. Comparison of the B3LYP energies of the two stereoisomers showed that the rccc conformer is more stable than its rctt counterpart for all the derivatives considered. However, calculations made with the double-hybrid Grimme's B97D functional confirmed the experimental observation that the relative stability depends on the type of the R substituents. These results clearly suggest that the B97D functional together with large enough basis sets (i.e. split-valence plus polarisation and diffuse functions) is sufficiently accurate for the purpose of describing the conformational features of these compounds. Computed electrostatic potential maps of the rccc of the different R-Pyg[4]arenes showed that a negative potential is present within the cavity of these compounds. In addition, it is observed that the size of this negative electrostatic potential depends on the electron-donating or electron-withdrawing character of the R substituents.
Biophysical Journal, 1995
Grand canonical Monte Carlo (GCMC) simulations are reported for aqueous solutions containing excess univalent salt (activities a, = 1.76-12.3 mM) and one of the following species: an octacationic rod-like ligand, L8I; a B-DNA oligomer with N phosphate charges (8 < N ' 100); or a complex resulting from the binding of L8+ at the center of an N-mer (24 < N 5 250). Simplified models of these multiply charged species are used in the GCMC simulations to predict the fundamental coulombic contributions to the following experimentally relevant properties: 1) the axial distance over which ligand binding affects local counterion concentrations at the surface of the N-mer; 2) the dependence on N of GCMC preferential interaction coefficients, FMC _ aC3/aC2 ,,Tl where C3 and C2 are, respectively, the molar concentrations of salt and the multiply charged species (ligand, N-mer or complex); and 3) the dependence on N of SaKobs d In KObS/d In a+ = A(+ 2F32J) where KObS is the equilibrium concentration quotient for the binding of L8+ to the center of an N-mer and A denotes the stoichiometric combination of terms, each of which pertains to a reactant or product J having ZJ charges. The participation of electrolyte ions in the ligand binding interaction is quantified by the magnitude of S K.bS, which reflects the net (stoichiometrically weighted) difference in the extent of thermodynamic binding of salt ions to the products and reactants. Results obtained here from GCMC simulations yield a picture of the salient molecular consequences of binding a cationic ligand, as well as thermodynamic predictions whose applicability can be tested experimentally. Formation of the central complex is predicted to cause a dramatic reduction in the surface counterion (e.g., Na+) concentration over a region including but extending well beyond the location of the ligand binding site. For binding a cationic ligand, SaKobs is predicted to be negative, indicating net electrolyte ion release in the binding process. At small enough N,-SaKobs is predicted to decrease strongly toward zero with decreasing N. At intermediate N,-SaKobs appears to exceed its limiting value as N,->°.
Bertoncini et al - J Phys Chem – 1990 - DOI 10.1021-j100378a050
1980, 102, 3900. (b) Bunton, C. A.; Gan, L.-H.; Moffatt, J. R.; Romsted, L. S.; Savelli, G . J . Phys. Chem. 1981, 85, 4118. 92, 2896. Kinetics. First-order rate constants, 4, for reactions with Brdecrease monotonically on addition of I-BuOH to 0.03 M sur-(14) (a) Mackay, R. A.; Hermansky, C. J. Phys. Chem. 1981,85,739. (b) Bunton, C. A.; de Buzzaccarini, F.; Hamed, F. H. (22) Otero, C.; Rodenas, E. Can.
Croat. Chem. Acta 2015, 88(3), 259–266.pdf
Redox kinetics of the reaction of an adipato bridged iron(III)-salen complex, [(Fe(salen))2adi] with dithionite ion, S2O4 2-, was investigated in perchloric acid at I = 0.05 mol dm -3 (NaClO4) and T = 29 ± 1 °C. Spectrophotometric titrations indicated consumption of one mole of S2O4 2per mole of [(Fe(salen))2adi] reduced. Under pseudo-first order conditions of [S2O4 2-] above ten-fold excess of concentration of [(Fe(salen))2adi], observed rates increased with increase in [S2O4 2-] and second order rate constants were fairly constant (0.285 ± 0.01 dm 3 mol -1 s -1 ) indicating first order dependence of the rate on [(Fe(salen))2adi]. A plot of logkobs versus log[S2O4 2-] was linear and gave a slope of 1.0 indicating first order dependence of the rate on [S2O4 2-]. The reaction rate increased with increase in [H + ] within 3 × 10 -3 mol dm -3 ≤ [H + ] ≤ 14 × 10 -3 mol dm -3 . The reaction was unaffected by variation of ionic strength and dielectric constant of the medium. Addition of anion and cation did not catalyze the reaction. The reaction has been analyzed on the basis of an inner-sphere mechanism mediated by proton transfer.