Erratum: Proton solvation in protic and aprotic solvents [J. Comput. Chem. 2015, 37, 1082–1091]

Abstract

The authors were using for dimethyl sulfoxide (DMSO) a value of the dielectric constant of 36.7, which is lower than the correct value of 46.7. We are sorry for this confusion. The purpose of this erratum is to demonstrate the consequences on the results using the correct value of the DMSO dielectric constant. With the larger value of the dielectric constant the individual electrostatic solvation energies of the protonated and deprotonated molecular species are all more negative. However, for the computation of pK A values differences of these solvation energies are used, where these changes are nearly compensated. As final result no change in the value of proton solvation in DMSO was obtained remaining at 2266.4 kcal/mol.[1]The individual computed pK A values exhibit minor changes (see Table 1) with a root mean square deviation (pK A -RMSD) of 0.42 and a mean signed deviation (pK A -MSD new-old ) of 20.2 between the new and old pK A values. The pK A -RMSD between computed and measured pK A values is with 0.65 (without outliers) slightly smaller than before, where it was 0.75. The value of pK A -MSD comp-exp remains practically the same.[1] Hence, pK A values seem to be robust against moderate deviations (less than 20%) of the dielectric constant used for the computation.It can be expected that this is less the case for variations of atomic radii and atomic partial charges.As an aprotic solvent DMSO does not possess polar hydrogen atoms. Due to the lack of polar hydrogens the atomic charges of the solvent molecules come less close to atoms of solute molecule than in case of a protic solvent like water. To account for this solvation effect the solute atomic radii must be enlarged compared to the atomic radii in water. For this purpose, we use radii enhancement factors, which are determined by minimizing the pK A

How to Predict the pKa of Any Compound in Any Solvent

“… 34 This is, however, in disagreement with earlier work which almost consistently suggests that the proton solvation energy should be similar to that in water or even be somewhat more negative; i.e., modeling results vary between −11.55 eV and −11.85 eV. 27 , 33 , 59 , 62 , 64 , 128 , 133 , 134 Comparable results were also obtained experimentally. 35 , 129 The only exception is the work of Carvalho et al 63 who with a solvation energy of −11.32 eV also predicted that protons in DMSO should be less stable than in water.…”

“…Computations reported in the literature so far on the other hand either rely on a p K a value in the solvent of interest 27 , 33 , 128 or a reference state of the proton in the gas phase. 58 − 64 The former modeling approach suffers mainly from the uncertainties associated with the determination of the experimental p K a values.…”

Copper(ii) thiosemicarbazone complexes induce marked ROS accumulation and promote nrf2-mediated antioxidant response in highly resistant breast cancer cells

“…The observed potential shifts in the anodic oxidation of 1-4 by replacing aprotic DMSO with proton-donating water environment were caused by expected different energy of solvation for DMSO and H 2 O and by involvement of protons in the redox process in water in contrast to the aprotic environment. 43,44 Interestingly, the lowest reduction potential E 1 pc = −0.27 V vs. Ag/AgCl was observed for 1 with terminal -NH 2 group in the ligand. For comparison, the redox potential in unbuffered aqueous solutions was recalculated vs. Fc + /Fc 0 using known redox potential of Ag/AgCl (0.197 V) and ferrocene (0.64 V) vs. Standard Hydrogen Electrode (SHE).…”

“…Many metal-free thiosemicarbazones, including Triapine, exhibit very high cytotoxicity up to nanomolar concentrations, [45][46][47][48] which was postulated to be related at least in part to their ribonucleotide reductase inhibitory potential, 18 but there are also examples of TSCs with moderate antiproliferative activity. 24,[42][43][44] Coordination of TSCs to copper(II) usually leads to an increase in antiproliferative activity of the resultant copper(II) complexes. 24,47 A notable exception is copper(II)-Triapine complex which showed a significant decrease in anticancer activity when compared to that of Triapine alone.…”

Predicted Gas‐Phase and Liquid‐Phase Acidities of Carborane Carboxylic and Dicarboxylic Acids

“…For pK a computations in solution, the free energy of the solvated proton is a critical parameter, usually computed as the contribution of the free energy of the proton in the gas‐phase at standard temperature and pressure (‐26.28 kJ⋅mol −1 at 298.15°K), which is obtained with the Sackur–Tetrode equation, and the free energy of proton solvation in MeCN [H + (g) → H + (MeCN)]. We use a value of 1067.34 kJ⋅mol −1 for the proton solvation in MeCN …”