The intrinsic view of ionization equilibria of polyprotic molecules

Borkovec, Michal; Koper, Ger J. M.; Spiess, Bernard

doi:10.1039/c4nj00655k

Cited by 5 publications

(5 citation statements)

References 41 publications

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“…Unbiased macroconstants for Suα-CD could only be deduced by the site-binding model (SB). Its mathematical elaboration has been published by Borkovec [47][48][49]; only the key concept is reiterated here using our notational system.…”

Section: The Microscopic Site-binding Modelmentioning

confidence: 99%

“…Choosing one intrinsic microconstant for each site and group pair interactivity parameters as iteration parameters to build up all the remaining microconstants [45,46] represents a more efficient strategy for the computer fitting of NMR titration curves. The site-binding (SB) or cluster expansion model by Borkovec [47][48][49] succeeded in resolving the complete microspeciation of large symmetric polyprotic molecules such as linear polyamines or dendrimers.…”

Section: Introductionmentioning

confidence: 99%

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Fully Symmetric Cyclodextrin Polycarboxylates: How to Determine Reliable Protonation Constants from NMR Titration Data

Kalydi

Ujj

Benkovics

et al. 2022

IJMS

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Acid-base properties of cyclodextrins (CDs), persubstituted at C-6 by 3-mercaptopropionic acid, sualphadex (Suα-CD), subetadex (Suβ-CD) and sugammadex (Suγ-CD, the antidote of neuromuscular blocking steroids) were studied by 1H NMR-pH titrations. For each CD, the severe overlap in protonation steps prevented the calculation of macroscopic pKa values using the standard data fitting model. Considering the full symmetry of polycarboxylate structures, we reduced the number of unknown NMR parameters in the “Q-fitting” or the novel “equidistant macroscopic” evaluation approaches. These models already provided pKa values, but some of them proved to be physically unrealistic, deceptively suggesting cooperativity in carboxylate protonations. The latter problem could be circumvented by adapting the microscopic site-binding (cluster expansion) model by Borkovec, which applies pairwise interactivity parameters to quantify the mutual basicity-decreasing effect of carboxylate protonations. Surprisingly, only a single averaged interactivity parameter could be calculated reliably besides the carboxylate ‘core’ microconstant for each CD derivative. The speciation of protonation isomers hence could not be resolved, but the optimized microscopic basicity parameters could be converted to the following sets of macroscopic pKa values: 3.84, 4.35, 4.81, 5.31, 5.78, 6.28 for Suα-CD; 3.82, 4.31, 4.73, 5.18, 5.64, 6.06, 6.54 for Suβ-CD and 3.83, 4.28, 4.65, 5.03, 5.43, 5.81, 6.18, 6.64 for Suγ-CD. The pH-dependent charge of these compounds can now be accurately calculated, in support of designing new analytical methods to exploit their charge-dependent molecular recognition such as in cyclodextrin-aided chiral capillary electrophoresis.

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Section: The Microscopic Site-binding Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fully Symmetric Cyclodextrin Polycarboxylates: How to Determine Reliable Protonation Constants from NMR Titration Data

Kalydi

Ujj

Benkovics

et al. 2022

IJMS

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“…1−5 As the number of basic sites grows, the number of microconstants increases exponentially; therefore for macromolecules only site-specific "group" constants are attainable 6 unless some constraints can be introduced on the microspeciation via symmetry in the compound. 7 Another approach to minimizing the number of unknown parameters in a microspeciation scheme is the cluster expansion model, 8 successfully implemented recently for symmetric octaprotic compounds. 9 A number of papers and book chapters describe the details of the experimental methods used for the determination of macro-and microconstants.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies covered the principles of microspeciation (i.e., determination of species-specific protonation constants) based on experimental techniques, such as classical potentiometry or spectroscopy-augmented titrimetric methods. − As the number of basic sites grows, the number of microconstants increases exponentially; therefore for macromolecules only site-specific “group” constants are attainable unless some constraints can be introduced on the microspeciation via symmetry in the compound . Another approach to minimizing the number of unknown parameters in a microspeciation scheme is the cluster expansion model, successfully implemented recently for symmetric octaprotic compounds …”

Section: Introductionmentioning

confidence: 99%

Estimating the Bias of Model Compounds for the Determination of Species-Specific Protonation Constants

Pálla,

Kolompár,

Mazák

et al. 2023

ACS Omega

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The previously unknown extent of the goodness of using model compounds for the microspeciation of polyprotic systems was studied. Mirror-symmetric dibasic compounds and their monosubstituted derivatives were investigated to quantify how the derivatives are appropriate models of the minor microspecies to be mimicked in various microspeciation systems. The results were analyzed using statistical methods. It was found that the respective O-methyl and S-methyl derivatives of phenols and thiols as well as the methyl esters of carboxylic acids are sufficiently good derivatives for microspeciation. It was also found that the methyl esters are superior to the carboxylic amides for modeling the –COOH moiety.

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“…Acid-base equilibria in weak polyelectrolytes represent the paradigmatic case of charge regulation in weak polyelectrolytes (due to the ubiquitous nature of proton ions in aqueous solution) and its study has been a classical topic in the past [7,8,9]. Among the different theoretical approximations used to describe the ionization properties in these systems, the site binding (SB) model has proven to be one of the most productive frameworks [10,11]. In this model, the ionization state of the molecule is defined as a set of protonating sites, which can adopt two possible states, i.e., protonated and deprotonated.…”

Section: Introductionmentioning

confidence: 99%

Dealing with long‐range interactions in the determination of polyelectrolyte ionization properties. Extension of the transfer matrix formalism to the full range of ionic strengths

Garcés

Madurga

Rey-Castro

et al. 2016

J Polym Sci B Polym Phys

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The ionization state of charged macromolecules in solution is usually determined by the extent of the binding processes. These processes are very sensitive to the ionic strength of the medium, which are of long-range nature. The ionization properties of weak polyelectrolytes can be described by means of Ising-type models, which is only feasible when long-range interactions are neglected. Here, this formalism is extended to include long-range interactions by introducing a modified free energy involving only effective short-range interaction parameters. These parameters can be systematically calculated by using the GibbsBogoliubov variational principle. The technique is illustrated with the calculation of titration curves of homogeneous and heterogeneous polyelectrolytes in 1 a wide range of ionic strengths. The correction of the site protonation free energy (first order correction) is enough to obtain an excellent agreement between theory and Monte Carlo simulations. Corrections to other cluster parameters (higher order corrections) are also implemented. In general, the correction to a particular parameter represents the average change in the long-range energy when a new interaction is created in the polyelectrolyte. The method presented here represents an improvement in the description of the ionization state of polyelectrolytes that can be relevant in a wide range of areas.

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The intrinsic view of ionization equilibria of polyprotic molecules

Abstract: The described intrinsic approach massively reduces the parameter number to describe microequilibria. The resulting intrinsic parameters yield insight into the protonation of polyprotic molecules.

Cited by 5 publications

References 41 publications

Fully Symmetric Cyclodextrin Polycarboxylates: How to Determine Reliable Protonation Constants from NMR Titration Data

Fully Symmetric Cyclodextrin Polycarboxylates: How to Determine Reliable Protonation Constants from NMR Titration Data

Estimating the Bias of Model Compounds for the Determination of Species-Specific Protonation Constants

Dealing with long‐range interactions in the determination of polyelectrolyte ionization properties. Extension of the transfer matrix formalism to the full range of ionic strengths

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