The acid dissociation constant is a key thermodynamic property, but large compilations of highly trustworthy data in non-aqueous solvents are scarce. This work presents a new partial digitization of a compilation, with corrections, of pKa data published originally by Kosuke Izutsu in 1990 as an official publication of the International Union of Pure and Applied Chemistry (IUPAC). The data span the six solvents nitromethane, N-methyl-2-pyrrolidone, dimethylacetamide, 4-methylpentan-2-one (or methyl isobutyl ketone), hexamethylphosphoramide, and sulfolane. Because the original data were not critically evaluated, we also include proposed systematic corrections to the data, which resolve major inconsistencies in the original data compilation. To contextualize this new dataset, we also present a numerical analysis of the recently-released IUPAC 2025 dataset for neutral acids in the solvents dimethyl sulfoxide, acetonitrile, dimethyl formamide, acetone, pyridine, tetrahydrofuran, and propylene carbonate, compiled by Leito and collaborators. We discuss the creation and contents of these digital data compilations, and analyze not only the pKa values, but also the overall reliability, methodology, and other available metadata. The Izutsu dataset is available at: https://doi.org/10.5281/zenodo.19626584 and the IUPAC 2025 dataset at https://doi.org/10.5281/zenodo.12608876.

Recognizing the importance of fluorine and deuterium in medicinal chemistry but hampered by the recent controversy surrounding PFAS, we chose to develop new reagents that allow the insertion of non-PFAS fluorinated motifs, such as the CD2F and CF2D fragments. Based on our previous work on the use of cyclic sulfoximines as reagents, the synthesis and measurement of pKa values of these new sulfoximines were compared to those of their so-called "open" analogues. This work enabled us to access the deuterated versions of these compounds. We then continued the comparison between these cyclic and open fragments by discussing their use as reagents and radical sources.

Equilibrium Brønsted acidity measurements have been established in 1,2-difluorobenzene (1,2-DFB), both in terms of acid pK a values measured using UV-vis spectrophotometry and unified pH (pHabs) values measured using differential potentiometry. The pK a values of 137 acids were obtained in 1,2-DFB, of which 33 have been directly measured, spanning 15 orders of magnitude of acidity. The rest have been estimated using pK a values in other solvents (acetonitrile, 1,2-dichloroethane). The pK a values have been anchored to the computational pK a values of 9 compounds. An experimental pHabs scale spanning more than 10 orders of magnitude has been established and aligned with the aqueous pH scale, resulting in a p H a b s H 2 O range from -0.6 to 10.0. The potentiometrically measured p H a b s H 2 O values and p H a b s H 2 O values calculated independently from the experimental pK a values anchored to computational reference values agree well, which demonstrates the solid foundation of the underlying theory. These results open the possibility of quantitatively describing and measuring acid-base processes in 1,2-DFB, including potentiometric and UV-vis spectrophotometric p H a b s H 2 O measurement.

Color vision relies on selective, reversible isomerization by visible light of a mixture of retinyl chromophores in photoreceptor cells. Synthetic molecular mimics of this wavelength-dependent induction of function are rare, despite the attractiveness of controlling chemical processes solely by the wavelength of incident light. Here, we report a color-responsive chemical system that is composed of a cationic receptor complex, two competing chiral anionic ligands, and two metastable photoacids with contrasting absorption properties. Tricyanofuran photoacids are synthesized with absorption maxima of varying wavelengths across the whole visible spectrum. Protons released by the photoacids upon selective irradiation reversibly mask the more basic receptor-bound ligand, leading to ligand exchange that can be observed as a shift in the circular dichroism (CD) spectrum of the reporter complex. A ≈90 nm separation between the absorbance maxima of the photoacids allowed each to be selectively photoisomerized in the presence of the other. The concentration of released protons, and hence the magnitude of the shift in CD response, are controlled by changing the wavelength of the incident visible light. Different output behaviors (OR/AND logic gates and wavelength detection) are programmed into the system by varying the relative proportions of the photoacids.

Predicting the physicochemical properties of ionizable solutes, including solubility and lipophilicity, is of broad significance. Such predictions rely on the accurate determination of solvation free energies for ions. However, the limited availability of high-quality reference data poses a challenge in developing accurate, inexpensive computational prediction methods. In this study, we address both issues of data quality and availability. We present three databases and models related to ionic phenomena: (1) 8,241 pKa data points across 8 solvents, (2) 5,536 gas-phase acidities from DLPNO-CCSD(T) QM calculations, and (3) 6,090 solvation free energies of anions across 8 solvents obtained from a thermodynamic cycle. We also report 6,088 solvation free energies of neutral conjugate solutes computed using the COSMO-RS method. The pKa data were obtained from the iBonD database, cleaned, and combined with a separate compilation of trustworthy reference pKa data. Gas-phase acidities were computed for most of the acids present in the pKa corpus. Leveraging these data, we compiled values for solvation free energies of anions. We then trained several graph neural network models, which can be used as an alternative to QM approaches to quickly estimate these properties. The pKa and gas-phase acidity models accept reaction SMILES strings of the acid dissociation as inputs, whereas the solvation energy model accepts the SMILES string of the anion. Our microscopic pKa model achieves good accuracy, with an overall test mean average error of 0.58 units on unseen solutes and 0.59 on the SAMPL7 challenge (the lowest error so far among multisolvent models). Our gas-phase acidity model had mean absolute errors slightly above 2 kcal mol-1 when evaluated against experimental data. The anionic solvation free energy model had mean absolute errors of less than 3 kcal mol-1 in several test evaluations, comparable to (though less reliable than) several widely used QM-based solvation models. The models and data are free and publicly available at doi.org/10.5281/zenodo.13987781.

Nitrogen heterocycles and aromatic amines are well-known and widely used compounds that are usually not seen as acids, although in organic solvents like acetonitrile (MeCN) or dimethyl sulfoxide (DMSO) their acidic properties can be observed. In this work, the acidities (pK a values) of 37 such weak NH acids were determined in acetonitrile and presented together with computational gas-phase acidities and literature pK a values in DMSO. In the course of the work the weakest acids range (from pK a 29 upward) of the MeCN acidity scale has been revised and expanded to around 33.5 by adding 31 compounds in that specific region and the span of experimental pK a values in MeCN is now more than 30 orders of magnitude. The relations between the structure and acidity of a selection of the studied compounds have been investigated in MeCN and DMSO. The measured pK a values in MeCN and the gathered pK a values in DMSO were used for a correlation analysis between the two solvents and for assessing the quality of pK a conversion equations. A number of pK a values have been predicted in MeCN from pK a values in DMSO via the correlation analysis and pK a conversion equations.

Aquatic dissolved organic matter (DOM) is an ultracomplex mixture of compounds covering a wide range of masses and with an unknown extent of isomeric complexity, making its structural elucidation and quantification highly challenging. Electrospray ionization high-resolution mass spectrometry (ESI-HRMS) has advanced DOM analysis, but accurate concentration determination remains limited by the lack of a response factor correction. Here, we address this limitation by introducing novel deuterated compounds as internal standards that mimic DOM structures. Using a d5-labeled compound free of isobaric interferences in DOM, we assessed ionization suppression in various aquatic sample extracts and improved concentration-based linearity in a coastal DOM reference material. Our results show that deuterated carboxylic acid-rich standards enable "pseudoquantification" by correcting for ionization suppression and instrument drift. Applying this approach, we estimate that DOM consists of 20-30% acids in river, coastal, and deep-ocean reference samples using an Orbitrap system. The same samples were estimated to contain 11-24% acids using 15T FT-ICR-MS, highlighting platform differences. Additionally, we establish a ∼1 ng L-1 feature detection limit for DOM compounds in seawater via a standard LC-MS gradient method. These findings demonstrate that deuterated standards provide a simple, practical way to improve DOM pseudoquantification, enhancing our understanding of its chemical composition in environmental studies.

This work focused on understanding the influence of dyeing methods and dye origin on the fluorescence spectra of wool yarns dyed with bloodred webcap (Cortinarius sanguineus), and exploring the potential and limitations of non-invasive fluorescence spectrometry in differentiating natural dyes on wool textiles. Wool fibers dyed with bloodred webcap specimens from five different geographic origins or with emodin standards, and using nine different mordanting procedures, were investigated using three-dimensional (3D) fiber optic fluorescence spectrometry, resulting in a dataset of 20 excitation-emission matrices (EEMs). In addition, the effect of self-absorption on EEMs of this dataset was investigated. The ability of the fluorescence-based method to discriminate dyes from different taxonomic families was also assessed by combining the bloodred webcap data with EEMs from a more diverse dataset which includes 18 different species. The dyeing method had some effect on the collected EEMs, potentially complicating the identification of a dye source in a historical textile if the mordanting procedure is unknown. The geographic origin of the fungi samples in this dataset showed minimal impact on the fluorescence spectra. Principal component analysis of a more diverse set of EEMs was helpful in differentiating dye taxonomic families, indicating utility of fluorescence spectrometry in qualitative determinations of some natural dye sources. While fluorescence alone may be insufficient for the unequivocal identification of natural dyes, this non-invasive, non-destructive, and rapid technique can provide useful additional information for identification when used in combination with other analytical techniques.

Phosphanes play an important role in various applications, serving as a class of organic bases with basicities spanning more than 30 orders of magnitude. Accessing comprehensive basicity data for phosphanes has been challenging due to scattered information across multiple sources and notable gaps in the existing data. In this report, we present basicities (pK(aH) values) of a diverse set of phosphanes, both newly measured or calculated and collected from the literature. We demonstrate that pK(aH) values can serve as an alternative to Tolman electronic parameters (TEP values) in evaluating the electronic properties of phosphanes. Additionally, we suggest parameters for assessing the steric properties of phosphanes without the need for preparation or calculation of metal-ligand complexes.

Identification of stereo- and positional isomers detected with high-resolution mass spectrometry (HRMS) is often challenging due to near-identical fragmentation spectra (MS2), similar retention times, and collision cross-section values (CCS). Here we address this challenge on the example of hydroxylated polychlorinated biphenyls (OH-PCBs) with the aim to (1) distinguish between isomers of OH-PCBs using two-dimensional ion mobility spectrometry (2D-IMS) and (2) investigate the structure of the fragments of OH-PCBs and their fragmentation mechanisms by ion mobility spectrometry coupled to high-resolution mass spectrometry (IMS-HRMS). The MS2 spectra as well as CCS values of the deprotonated molecule and fragment ions were measured for 18 OH-PCBs using flow injections coupled to a cyclic IMS-HRMS. The MS2 spectra as well as the CCS values of the parent and fragment ions were similar between parent compound isomers; however, ion mobility separation of the fragment ions is hinting at the formation of isomeric fragments. Different parent compound isomers also yielded different numbers of isomeric fragment mobilogram peaks giving new insights into the fragmentation of these compounds and indicating new possibilities for identification. For spectral interpretation, Gibbs free energies and CCS values for the fragment ions of 4'-OH-CB35, 4'-OH-CB79, 2-OH-CB77 and 4-OH-CB107 were calculated and enabled assignment of structures to the isomeric mobilogram peaks of [M-H-HCl]- fragments. Finally, further fragmentation of the isomeric fragments revealed different fragmentation pathways depending on the isomeric fragment ions.

Quantitative assessment of the first acidity constant (pKa) for BFC (27.6 in CH3CN) and FIC (27.8 in CH3CN) shows the methylene protons to be significantly more acidic than those in related cyclopentadiene (32 in CH3CN), indene (34 in CH3CN), or fluorene (37 in CH3CN) and comparable to the methine of 9-perfluorophenylfluorene (28.14 in CH3CN). This work reports quantitative pKa values of BFC and FIC, places those values in a broadened context of CpH-cognate hydrocarbon acidity and presents a Clar–Loschmidt graph perspective to help understand the “surprises”.

Despite the numerous published syntheses and applications of sulfoximines, very few studies describe their physico-chemical properties and in particular their acidic, basic and lipophilic or hydrophilic characters. We report for the first time the acidity values (pKa) of fluorinated sulfoximines in water and in acetonitrile, as well as the basicity (pKaH) measurements of fluorinated and non-fluorinated sulfoximines in acetonitrile. The same sulfoximine library was also studied in terms of lipophilicity with measurement of the Hansch parameters of the sulfoximine moieties. Finally, these new data allowed us to optimize the N-alkylation reaction of fluorinated sulfoximines.

A new group of bases with benzophenoneiminyl (bpi) moiety has been synthesized and characterized in this work. The title compound tris(benzophenoneimino)phosphane (P(bpi)(3)) 1 was prepared with a convenient one-pot approach: benzophenone imine was deprotonated using MeMgCl and reacted with PBr3 in diglyme. The method could be considered as a method of choice for preparing other (amino)phosphanes in case lithio-intermediates and/or protonated phosphane is out of consideration. Phosphane 1 is further used to prepare a range of related phosphonium cations and phosphazenes. Phosphonium cations were deprotonated to assess the stability of the resulting phosphonium ylides. In some cases, the bulky substances were capable of forming P-N heterocycles. Experimental (MeCN) and computational (MeCN, THF, gas-phase) basicities of benzophenone imine, phosphane 1, phosphonium ylides, and phosphazenes, as well as some representative XRD structures, are presented and discussed.

The linking of phosphoric acids via covalent or mechanical bonds has proven to be a successful strategy for the design of novel organocatalysts. Here, we present the first systematic investigation of singly-linked and macrocyclic bisphosphoric acids, including their synthesis and their application in phase-transfer and Brønsted acid catalysis. We found that the novel bisphosphoric acids show dramatically increased enantioselectivities in comparison to their monophosphoric acid analogues. However, the nature, length and number of linkers has a profound influence on the enantioselectivities. In the asymmetric dearomative fluorination via phase-transfer catalysis, bisphosphoric acids with a single, rigid bisalkyne-linker give the best results with moderate to good enantiomeric excesses. In contrast, bisphosphoric acids with flexible linkers give excellent enantioselectivities in the transfer-hydrogenation of quinolines via cooperative Brønsted acid catalysis. In the latter case, sufficiently long linkers are needed for high stereoselectivities, as found experimentally and supported by DFT calculations.

In this paper, fluorinated compounds based on sulfolane, cyclopentanone, and gamma-butyrolactone are studied computationally, focusing on their applicability in electrochemical devices and acid–base-related studies. Candidates for solvents with (1) high polarity, (2) good electrochemical stability, and (3) low basicity were searched for. Some of the compounds are studied here for the first time. Electrochemical stabilities, dielectric constants, boiling points, basicities, and lipophilicities were estimated using DFT and COSMO-RS methods with empirical corrections. The effect of fluorination on these properties as well as the bond parameters was studied. The possible synthesis routes of the proposed compounds are outlined. Some molecules display a combination of estimated properties favorable for a solvent, although none of the studied compounds are expected to surpass acetonitrile and propylene carbonate by the width of the electrochemical stability window.

Multidimensional fluorescence spectroscopy was assessed as a non-invasive and non-destructive method for the analysis of components in natural textile dyes. Results demonstrate that components in the natural dyes fluoresce and wool's intrinsic fluorescence is, in many cases, not a considerable analytical interferent. In the case of some self-dyed reference yarns, like those dyed with northern and lady's bedstraws, wood horsetail, safflower, salted shield lichen, dyer's madder and cochineal, the fluorescence excitation-emission matrices (EEMs) are sufficiently characteristic for using them as a primary means of identification (or assignment to a family of dyes). With most of the studied yellow and green dyes (heather, silver birch, some bloodred webcap treatments, alkanet), however, the spectra can be used as additional information for identification. This study reports multidimensional fluorescence data for a collection of wools dyed with natural dyes (31 dyed wool yarn samples that were self-dyed with 18 different natural dyes) that were used as references in a case study of two historical textiles for which liquid chromatography-mass spectrometry was used as a confirmatory technique. Given its utility as a rapid and non-destructive/non-invasive method with information-rich multidimensional EEM output, the front-face fluorescence spectroscopy of surfaces using a fiber optic probe is a promising technique for the analysis of dyes on cultural heritage textiles.

Solubilities of mono-aminoacridines (AAs) in a variety of solvents were studied computationally using COSMO-RS method and selectively confirmed by experiment (liquid chromatography and gravimetry). The results confirm the reliability of COSMO-RS for ranking solvents on the basis of dissolving a specific AA, but not ranking the solubilities of different AAs in the same solvent. Pyrrolidine and some pyrrolidine-based mixtures were predicted to deliver outstandingly high solubilities of AAs (10-30 % by mass, depending on the compound). Hydrogen bonding was found to have a considerable role in the solubility of AAs, which can act as hydrogen bond donors and acceptors. The obtained data and conclusions can facilitate solvent selection for purification of AAs, sample preparation for MALDI-MS if an AA is used as a matrix, and can be helpful for solubility-related applications involving other compounds.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The syntheses of hexabrominated closo-carborates decorated with different chiral Binol-derived phosphonates and their conjugate acids are described. X-ray diffraction analysis reveals a polymeric structure for the sodium salt with the anionic units connected by [B-Br-Na-O & boxH;P](+) linkages. For the acid, coordination of the proton to the phosphonate's P & boxH;O oxygen atom is assumed. The pK(a) value was estimated by combining experiments and computations. Application of these Br & oslash;nsted acids as chiral catalysts in an imino-ene and a Mukaiyama-Mannich reaction was moderately successful.

This work presents a compilation of binding constant (logKass) values in DMSO-d6/H2O (0.5% m/m) for a variety of receptors with 12 carboxylate anions (formate, acetate, lactate, pivalate, sorbate, hexanoate, benzoate, glyphosate, glucuronate, ibuprofen, naproxen, and ketoprofen). A total of 489 logKass values are listed for 100 anion receptor molecules. Most logKass values originate from previously published articles, along with some values for previously unpublished receptor molecules, spanning a workflow of 8 years. The purpose of this study is to serve as a comprehensive information source for selecting suitable receptor candidates to be used in practical carboxylate sensing applications, such as constructing ion-selective electrodes (ISE-s). To support such decision making, all receptors are presented together with lipophilicity (logPo/w) data.