scholarly journals On the Use of Aqueous Metal-Aqua pKa Values as a Descriptor of Lewis Acidity

2020 ◽  
Author(s):  
Amit Kumar ◽  
James Blakemore
Keyword(s):  
Metal Ions ◽  
Triphenylphosphine Oxide ◽  
Lewis Acidity ◽  
Pka Values ◽  
Chemical Systems ◽  
Monovalent Ions ◽  
Aqueous Pka ◽  
Multiple Species ◽  
Aqueous Conditions ◽  
Direct Measures

The behavior of Lewis acidic metal ions in multimetallic systems has become a subject of intense interest in recent years. Parametrizing the behavior of these ions in non-aqueous conditions, commonly used in the field, is challenging due to the lack of direct measures of the Lewis acidity of metal ions in polar organic solvents. Here, we report the use of triphenylphosphine oxide (TPPO) as a 31P nuclear magnetic resonance (NMR) probe to quantify the Lewis acidity of a library of metal triflate salts using the Gutmann-Beckett method. A plot of the pKa values of the corresponding metal-aqua species, [M(H2O)m]n+, measured in H2O, vs. the 31P NMR shifts of TPPO in the presence of these metals in deuterated acetonitrile (d3-MeCN) and deuterated dichloromethane (CD2Cl2) displays a tightly co-linear relationship, suggesting similar behavior for these ions in water, d3-MeCN, and CD2Cl2. This collinearity reinforces the utility of the common approach of using the aqueous pKa values as a descriptor of Lewis acidity, regardless of the solvent used in the immediate experiments, and provides an insight into the usefulness of this descriptor in wide-ranging applications. Titration studies in d3-MeCNsuggest 1:1 binding of TPPO with monovalent ions, greater than 1:1 binding with divalent ions, and formation of multiple species with the highly Lewis acidic trivalent ions. Together, these data suggest that both aqueous pKa values and other single-measurement descriptors, while useful, provide only a snapshot of the influence of Lewis acidity on multimetallic chemical systems.

scholarly journals On the Use of Aqueous Metal-Aqua pKa Values as a Descriptor of Lewis Acidity

2020 ◽  
Author(s):  
Amit Kumar ◽  
James Blakemore
Keyword(s):  
Metal Ions ◽  
Triphenylphosphine Oxide ◽  
Lewis Acidity ◽  
Pka Values ◽  
Chemical Systems ◽  
Monovalent Ions ◽  
Aqueous Pka ◽  
Multiple Species ◽  
Aqueous Conditions ◽  
Direct Measures

The behavior of Lewis acidic metal ions in multimetallic systems has become a subject of intense interest in recent years. Parametrizing the behavior of these ions in non-aqueous conditions, commonly used in the field, is challenging due to the lack of direct measures of the Lewis acidity of metal ions in polar organic solvents. Here, we report the use of triphenylphosphine oxide (TPPO) as a 31P nuclear magnetic resonance (NMR) probe to quantify the Lewis acidity of a library of metal triflate salts using the Gutmann-Beckett method. A plot of the pKa values of the corresponding metal-aqua species, [M(H2O)m]n+, measured in H2O, vs. the 31P NMR shifts of TPPO in the presence of these metals in deuterated acetonitrile (d3-MeCN) and deuterated dichloromethane (CD2Cl2) displays a tightly co-linear relationship, suggesting similar behavior for these ions in water, d3-MeCN, and CD2Cl2. This collinearity reinforces the utility of the common approach of using the aqueous pKa values as a descriptor of Lewis acidity, regardless of the solvent used in the immediate experiments, and provides an insight into the usefulness of this descriptor in wide-ranging applications. Titration studies in d3-MeCNsuggest 1:1 binding of TPPO with monovalent ions, greater than 1:1 binding with divalent ions, and formation of multiple species with the highly Lewis acidic trivalent ions. Together, these data suggest that both aqueous pKa values and other single-measurement descriptors, while useful, provide only a snapshot of the influence of Lewis acidity on multimetallic chemical systems.

scholarly journals Ring-fused porphyrins: extension of π-conjugation significantly affects the aromaticity and optical properties of the porphyrin π-systems and the Lewis acidity of the central metal ions

2015 ◽  
Vol 17 (22) ◽  
pp. 15001-15011 ◽  
Author(s):  
Yuta Saegusa ◽  
Tomoya Ishizuka ◽  
Keiyu Komamura ◽  
Soji Shimizu ◽  
Hiroaki Kotani ◽  
...  
Keyword(s):  
Optical Properties ◽  
Metal Ions ◽  
Lewis Acidity ◽  
Central Metal ◽  
Ring Fusion ◽  
Homo Lumo

The ring fusion with five-membered rings causes not only the narrowed HOMO–LUMO gaps but also the contribution of anti-aromatic resonance forms.

An Assessment of Theoretical Protocols for Calculation of the pKa Values of the Prototype Imidazolium Cation

2004 ◽  
Vol 57 (12) ◽  
pp. 1205 ◽  
Author(s):  
Alison M. Magill ◽  
Brian F. Yates
Keyword(s):  
Excellent Agreement ◽  
Basis Set ◽  
Hydrogen Atoms ◽  
Imidazolium Cation ◽  
Pka Values ◽  
Experimental Estimate ◽  
Pka Calculation ◽  
Complete Basis Set ◽  
Aqueous Pka ◽  
Experimental Values

The highly accurate complete basis set method CBS-QB3 has been used in conjunction with the conductor-like polarized continuum (CPCM) method to predict the aqueous pKa values for the three different hydrogen atoms in the imidazolium cation. Excellent agreement was obtained with the available experimental values. The pKa for the deprotonation of imidazole was also calculated and found to be quite different from the experimental estimate. The protocol for the pKa calculation was carefully analyzed and some recommendations made about the choice of levels of theory.

Ionically bound metalloporphyrin pairs on solid polymer support

2001 ◽  
Vol 05 (11) ◽  
pp. 763-766 ◽  
Author(s):  
MIKKI V. VINODU ◽  
M. PADMANABHAN
Keyword(s):  
Metal Ions ◽  
Solid Polymer ◽  
Polymer Support ◽  
Central Metal ◽  
Free Base ◽  
Cationic Porphyrins ◽  
Pyridyl Porphyrins ◽  
Aqueous Conditions ◽  
Covalently Bound

The present work demonstrates a simple and elegant strategy by which synthetically simple porphyrins are grafted on solid polymer support to generate porphyrin pairs held together by strong coulombic forces. Metalloporphyrins of tetra(4-pyridyl)porphyrins (MTPyP) were reacted with chloromethylated polystyrene (PS) beads to get covalently bound monocationic porphyrins on the polymer support (PS–MTPyP+). These were then converted to their tetracationic species (PS–MTMe3PyP4+) by exhaustive quaternisation, using CH 3 I . These polymer-grafted cationic porphyrins were made to react with tetraanionic p-sulphonated phenylporphyrins (MTPPS4-) in aqueous conditions. Analysis showed that the PS–MTMe3PyP4+ take up MTPPS4- in exactly 1:1 stoichiometry to form strongly bound (ionically) porphyrin pairs. A variety of homo- and hetero-porphyrin pairs involving central metal ions like Mn , Co , Cu , Zn and Ag and also free-base porphyrins are generated by this strategy.

scholarly journals Experiment stands corrected: accurate prediction of the aqueous pKa values of sulfonamide drugs using equilibrium bond lengths

2019 ◽  
Vol 10 (25) ◽  
pp. 6368-6381 ◽  
Author(s):  
Beth A. Caine ◽  
Maddalena Bronzato ◽  
Paul L. A. Popelier
Keyword(s):  
Accurate Prediction ◽  
Strongly Correlated ◽  
Pka Values ◽  
Bond Lengths ◽  
Linear Relationships ◽  
Aqueous Pka ◽  
First Time ◽  
Sulfonamide Group

We show here for the first time that strongly correlated linear relationships exist between equilibrium bond lengths of the sulfonamide group and aqueous pKa values.

scholarly journals The AIBLHiCoS Method: Predicting Aqueous pKa Values from Gas-Phase Equilibrium Bond Lengths

2016 ◽  
Vol 56 (3) ◽  
pp. 471-483 ◽  
Author(s):  
Cate Anstöter ◽  
Beth A. Caine ◽  
Paul L. A. Popelier
Keyword(s):  
Phase Equilibrium ◽  
Gas Phase ◽  
Pka Values ◽  
Bond Lengths ◽  
Aqueous Pka

Computational calculation of absolute aqueous pKa values for phenols

2013 ◽  
Vol 1019 ◽  
pp. 55-60 ◽  
Author(s):  
Ian D. Cunningham ◽  
Kabir Bhaila ◽  
David C. Povey
Keyword(s):  
Pka Values ◽  
Aqueous Pka ◽  
Computational Calculation
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