Acceptable Capability Research Articles

Computational modeling of air pollutants for aquatic risk: Prediction of ecological toxicity and exploring structural characteristics

Assessing the aquatic toxicity originating from air pollutants is essential in sustaining water resources and maintaining the ecosystem's safety. Quantitative structure-activity relationship (QSAR) models provide a computational tool for predicting pollutant toxicity, facilitating the identification/evaluation of the contaminants and identifying responsible structural fragments. One-vs-all (OvA) QSAR is a tailored approach to address multi-class QSAR problems. The study aims to determine five distinct levels of aquatic hazard categories for airborne pollutants using OvA-QSAR modeling containing 254 air contaminants. This QSAR analysis reveals the critical descriptors of air pollutants to target for molecular modification. Various factors, including the selection of relevant mechanistic descriptors, data quality, and outliers, determine the reliability of QSAR models. By employing feature selection and outlier identification approaches, the robustness and accuracy of our QSAR models were significantly increased, leading to more reliable predictions in chemical hazard assessment. The results revealed that models using the Random Forest algorithm performed the best based on the selected descriptors, with internal and external validation accuracy ranging from 71.90% to 97.53% and 76.47%–98.03%, respectively. This study indicated that the aquatic risk of air contaminants might be attributed predominantly to their sp3/sp2 carbon ratio, hydrogen-bond acceptor capability, hydrophilicity/lipophilicity, and van der Waals volumes. These structures can be critical in developing innovative strategies to mitigate or avoid the chemicals' harmful effects. Supporting air quality improvement, this study contributes to the rapid implementation of measures to protect aquatic ecosystems affected by air pollution.

Triazoles in Medicinal Chemistry: Physicochemical Properties, Bioisosterism, and Application.

Triazole demonstrates distinctive physicochemical properties, characterized by weak basicity, various dipole moments, and significant dual hydrogen bond acceptor and donor capabilities. These features are poised to play a pivotal role in drug-target interactions. The inherent polarity of triazole contributes to its lower logP, suggesting the potential improvement in water solubility. The metabolic stability of triazole adds additional value to drug discovery. Moreover, the metal-binding capacity of the nitrogen atom lone pair electrons of triazole has broad applications in the development of metal chelators and antifungal agents. This Perspective aims to underscore the unique physicochemical attributes of triazole and its application. A comparative analysis involving triazole isomers and other heterocycles provides guiding insights for the subsequent design of triazoles, with the hope of offering valuable considerations for designing other heterocycles in medicinal chemistry.

Hydration of Propargyl Esters Catalyzed by Gold(I) Complexes with Phosphoramidite Calix[4]pyrrole Cavitands as Ligands.

We report the synthesis and characterization of two diastereomeric phosphoramidite calix[4]pyrrole cavitands and their corresponding gold(I) complexes, 2in•Au(I)•Cl and 2out•Au(I)•Cl, featuring the metal center directed inward and outward with respect to their aromatic cavity. We studied the catalytic activity of the complexes in the hydration of a series of propargyl esters as the benchmarking reaction. All substrates were equipped with a six-membered ring substituent either lacking or including a polar group featuring different hydrogen bond acceptor (HBA) capabilities. We designed the substrates with the polar group to form 1:1 inclusion complexes of different stabilities with the catalysts. In the case of 2in•Au(I)•OTf, the 1:1 complex placed the alkynyl group of the bound substrate close to the metal center. We compared the obtained results with those of a model phosphoramidite gold(I) complex lacking a calix[4]pyrrole cavity. We found that for all catalysts, the presence of an increasingly polar HBA group in the substrate provoked a decrease in the hydration rate constants. We attributed this result to the competing coordination of the HBA group of the substrate for the Au(I) metal center of the catalysts.

Spectrofluorometric investigations on the solvent effects on the photocyclization reaction of diclofenac

The solvent effects on the photochemical conversion rate of the photosensitizing drug diclofenac (DCF) were investigated using steady-state fluorescence spectroscopy. The spectral information obtained for the photochemical reaction of DCF in a set of neat solvents demonstrates that the photoconversion reaction rate of DCF is not only medium polarity dependent but also hydrogen-bonding dependent. The solvent effects were qualitatively and quantitatively assessed employing various solvatochromic models, including multi-parameter linear regression analysis (MLRA). Interestingly, the MLRA results (R = 0.99) revealed that the photoconversion rate increases with increasing solvent polarizability (π*) and H-bond donor capability (α), whereas the rate decreases with increasing hydrogen-bond acceptor capability (β). However, predominant effect of the solvent acidity compared to basicity and polarizability was observed. A hypothesis rationalizing the effects of H-bonding and medium polarity on DCF photoconversion reaction is presented and discussed.

Zwitterionic Polymeric Sulfur Ylides with Minimal Charge Separation Open a New Generation of Antifouling and Bactericidal Materials.

Zwitterionic polymers are widely employed hydrophilic building blocks for antifouling coatings with numerous applications across a wide range of fields, including but not limited to biomedical science, drug delivery and nanotechnology. Zwitterionic polymers are considered as an attractive alternative to polyethylene glycol because of their biocompatibility and effectiveness to preventformation of biofilms. To this end, zwitterionic polymers are classified in two categories, namely polybetaines and polyampholytes. Yet, despite a fundamental interest to drive the development of new antifouling materials, the chemical composition of zwitterionic polymer remains severely limited. Here, we show that poly(sulfur ylides) thatbelongto the largely overlooked class of poly(ylides),effectively prevent theformation of biofilms from pathogenic bacteria. While surface energy analysis reveals strong hydrogen-bond acceptor capabilities of poly(sulfur ylide), membrane damage of pathogenic bacteria induced by poly(sulfur ylides) indicates toxicity towards bacteria while not affecting eucaryotic cells. Such synergistic effect of poly(sulfur ylides) offers distinct advantages over polyethylene glycol when designing new antifouling materials. We expect that our findings will pave the way for the development of a range of ylide-based materials with antifouling properties that have yet to be explored, opening up new directions at the interface of chemistry, biology, and material science.

Zwitterionic Polymeric Sulfur Ylides with Minimal Charge Separation Open a New Generation of Antifouling and Bactericidal Materials**

AbstractZwitterionic polymers are widely employed hydrophilic building blocks for antifouling coatings with numerous applications across a wide range of fields, including but not limited to biomedical science, drug delivery and nanotechnology. Zwitterionic polymers are considered as an attractive alternative to polyethylene glycol because of their biocompatibility and effectiveness to prevent formation of biofilms. To this end, zwitterionic polymers are classified in two categories, namely polybetaines and polyampholytes. Yet, despite a fundamental interest to drive the development of new antifouling materials, the chemical composition of zwitterionic polymer remains severely limited. Here, we show that poly(sulfur ylides) that belong to the largely overlooked class of poly(ylides), effectively prevent the formation of biofilms from pathogenic bacteria. While surface energy analysis reveals strong hydrogen‐bond acceptor capabilities of poly(sulfur ylide), membrane damage of pathogenic bacteria induced by poly(sulfur ylides) indicates toxicity towards bacteria while not affecting eucaryotic cells. Such synergistic effect of poly(sulfur ylides) offers distinct advantages over polyethylene glycol when designing new antifouling materials. We expect that our findings will pave the way for the development of a range of ylide‐based materials with antifouling properties that have yet to be explored, opening up new directions at the interface of chemistry, biology, and material science.

Choline chloride-water mixtures as new generation of green solvents: A comprehensive physico-chemical study

Natural deep eutectic solvents (NADES) are an increasingly appreciated class of mixtures composed by eco-sustainable and environmentally responsible components with hydrogen bonding (HB) donor and acceptor capabilities that enable the establishment of an extended HB network. The latter eventually leads to a substantial drop in the mixture melting point with respect to the one of the ideal mixture. Water-based NADES represent an exciting system that responds to the above mentioned criteria and contain water as a major component, rather than as an impurity or a deliberately added minor ingredient. Choline Chloride (ChCl, a well known HB acceptor in DES systems) forms NADES when mixed with water, which plays the role of HB donor. Several applications have already been identified for this system, but chemical physical properties of choline-rich mixtures, including the DES concentration, are not well established, yet. In order to overcame this limitation and introduce a subsequent, more systematic investigation of atomistic organization in these mixtures, here we report results from a series of chemical physical characterizations of water:ChCl with ratio ranging from 2 to 10 between ca. 280 and 330 K. Calorimetric measurements, density, viscosity, electric conductivity, refractive index, X-ray diffraction patterns and several 1H and 35Cl NMR spectroscopy observables are reported and compared with literature (when available). The deep eutectic nature of the water: ChCl 4:1 mixture is assessed, leading to the individuation of aquoline, as the corresponding DES. The other chemical physical properties are observed to vary, upon water content, in a monotone way, without abrupt changes across the eutectic concentration, thus providing support for the exploitation of the ChCl/water class of solvents, with tunable chemical-physical properties across their wide liquid range.

Designed and synthesized de novo ANTPABA-PDI nanomaterial as an acceptor in inverted solar cell at ambient atmosphere

In this work, a novel soluble and air-stable electron acceptor containing perylenediimide moiety named ANTPABA-PDI was designed and synthesized with band gap 1.78eV and that was used as non-fullerene acceptor material. ANTPABA-PDI possess not only good solubility but also much lower LUMO (lowest unoccupied molecular orbital) energy level. Furthermore, its excellent electron acceptor capability also supported by density functional theory calculation which validates the experimental observations. Inverted organic solar cell has been fabricated using ANTPABA-PDI along with P3HT as standard donor material in ambient atmosphere. The device, after characterization in open air, exhibited a power conversion efficiency of 1.70%. This is the first ever PDI based organic solar cell that has been fabricated completely in ambient atmosphere. The characterizations of the device have also been performed in ambient atmosphere. This kind of stable organic material can easily be used in fabricating organic solar cell and therefore it can be used as the best alternative as non-fullerene acceptor materials.

Competitor hydrogen-bond acceptors in the SP(NH)3-based structures: Comparison of structural features – Computational/database and experimental

The phosphorothioic triamides (4-Cl-C6H4CH2NH)3P(S) (I) and (4-CH3-C6H4CH2NH)3P(S) (II) were synthesized to study their coordination behaviors towards Hg(II) cation. The resulting complexes, [(4-Cl-C6H4CH2NH)3P(S)]2Hg2Cl4 (III) and [(4-CH3-C6H4CH2NH)3P(S)]2Hg2Cl4 (IV), are the first examples of mercury complexes with SP(NHR)3 ligands characterized by X-ray crystallography. The presence of NH/CH units and some potential competitor acceptors with moderate/weak acceptor capabilities (sulfur, chlorine and π system) provides the opportunity to study the hydrogen bond elements of (I), (III) and (IV), structurally and of all four compounds theoretically. The strengths of inter- and intramolecular hydrogen bonds were assessed by quantum chemical calculations (Atoms In Molecules (AIM), and Natural Bond Orbital (NBO)), and the internal interactions were further examined by reduced density gradient (RDG) analysis. The differences/similarities of structures were addressed in the view point of geometry, conformations related to flexible substituted benzyl moieties, crowding in the structures and non-bonded contacts, stabilization of four-membered Hg2Cl2 rings and some topics related to solution nuclear magnetic resonance studies (chemical shifts and coupling constants). The similarity of structures investigated allowed for a precise assignment of vibrational frequencies. A survey of the Hg—SP segment in the Cambridge Structural Database shows that the Hg—S bond lengths in (III) and (IV) are among the smallest Hg—S bonds in the structures with the thiophosphoryl-holding ligands.

Predicting Bile and Lipid Interaction for Drug Substances.

Predicting biopharmaceutical characteristics and food effects for drug substances may substantially leverage rational formulation outcomes. We established a bile and lipid interaction prediction model for new drug substances and further explored the model for the prediction of bile-related food effects. One hundred and forty-one drugs were categorized as bile and/or lipid interacting and noninteracting drugs using 1H nuclear magnetic resonance (NMR) spectroscopy. Quantitative structure-property relationship modeling with molecular descriptors was applied to predict a drug's interaction with bile and/or lipids. Bile interaction, for example, was indicated by two descriptors characterizing polarity and lipophilicity with a high balanced accuracy of 0.8. Furthermore, the predicted bile interaction correlated with a positive food effect. Reliable prediction of drug substance interaction with lipids required four molecular descriptors with a balanced accuracy of 0.7. These described a drug's shape, lipophilicity, aromaticity, and hydrogen bond acceptor capability. In conclusion, reliable models might be found through drug libraries characterized for bile interaction by NMR. Furthermore, there is potential for predicting bile-related positive food effects.

Donation and back-donation in cis- and trans-[(η5-C5H5)Fe(η1-CO)(μ-CO)]2 tautomers: Which relative is more generous? An ETS-NOCV bond analysis

The ETS-NOCV bond analysis has been exploited to quantitatively estimate donation and back-donation properties of [(η5-C5H5)]−, CO, and FeI in the cis-/trans-[(η5-C5H5)Fe(η1-CO)(μ-CO)]2 (cis-I/trans-I) tautomers. Theoretical outcomes indicate that the Fe-CO bond, regardless to the CO monoapto (η1-) or bridging (μ-) coordination, has a sizeable π Fe → CO back-bonding contribution, which is stronger in trans-I than in cis-I. Moreover, [(η5-C5H5)]− has the weakest back-donation acceptor capability. The back-bonding behaviour of the Fe → η1-CO interaction well agrees with the experimental symmetric/antisymmetric infrared νCO (sνη1-CO/aνη1-CO) trend for cis-I and trans-I and further confirms the infrared classical behaviour of the η1-CO group in this class of complexes.

Sulfoximine‐Directed Arene ortho‐Lithiation

AbstractSulfoximines are an interesting class of compounds, which exhibit Brønsted and Lewis basicity, nucleophilicity, C−H acidity, N−H acidity, hydrogen‐bond acceptor capability and chirality. Sulfoximines have received renewed interest in recent times, since incorporation of a sulfoximine group can provide drug candidates with favorable properties. The synthesis and N−H, α‐C−H and o‐C−H functionalization of sulfoximines are currently topics of considerable interest. This Minireview describes the sulfoximine‐directed arene ortho‐lithiation and the synthesis of ortho‐substituted S‐aryl sulfoximines. Comparison between the sulfoximine and sulfone group shows that both are equally potent directors in arene ortho‐lithiation. Double ortho‐lithiation of S‐phenyl sulfoximines affords o,o'‐dilithiosulfoximines, which undergo a stereoretentive rearrangement to o‐sulfinylanilines. S‐Phenyl sulfoximines, carrying a α‐hydrogen atom, are amendable to a selective ortho‐lithiation to give o‐lithiosulfoximines, which suffer transmetalation to the α‐lithiosulfoximines at ambient temperatures. Double lithiation of S‐phenyl N−H sulfoximines gives access to o,N‐dilithiosulfoximines, the reaction of which with biselectrophiles yields bicyclic sulfoximines.

Chloropentaphenyldisiloxane—Model Study on Intermolecular Interactions in the Crystal Structure of a Monofunctionalized Disiloxane

Small functional siloxane units have gained great interest as molecular model systems for mimicking more complex silicate structures both in nature and in materials chemistry. The crystal structure of chloropentaphenyldisiloxane, which was synthesized for the first time, was elucidated by single-crystal X-ray diffraction analysis. The molecular crystal packing was studied in detail using state-of-the-art Hirshfeld surface analysis together with a two-dimensional fingerprint mapping of the intermolecular interactions. It was found that the phenyl C–H bonds act as donors for both weak C–H···π and C–H···Cl hydrogen bond interactions. The influence of intramolecular Si–O–Si bond parameters on the acceptor capability of functional groups in intermolecular hydrogen bond interactions is discussed.

π-Bridge Substitution in DASAs: The Subtle Equilibrium between Photochemical Improvements and Thermal Control*.

Donor-acceptor Stenhouse adducts (DASAs) are playing an outstanding role as innovative and versatile photoswitches. Until now, all the efforts have been spent on modifying the donor and acceptor moieties to modulate the absorption energy and improve the cyclization and reversion kinetics. However, there is a strong dependence on specific structural modifications and a lack of predictive behavior, mostly owing to the complex photoswitching mechanism. Here, by means of a combined experimental and theoretical study, the effect of chemical modification of the π-bridge linking the donor and acceptor moieties is systematically explored, revealing the significant impact on the absorption, photocyclization, and relative stability of the open form. In particular, a position along the π-bridge is found to be the most suited to redshift the absorption while preserving the cyclization. However, thermal back-reaction to the initial isomer is blocked. These effects are explained in terms of an increased acceptor capability offered by the π-bridge substituent that can be modulated. This strategy opens the path toward derivatives with infra-red absorption and a potential anchoring point for further functionalization.

Structural Consequences of the 1,2,3-Triazole as an Amide Bioisostere in Analogues of the Cystic Fibrosis Drugs VX-809 and VX-770.

Although the 1,2,3-triazole is a commonly used amide bioisostere in medicinal chemistry, the structural implications of this replacement have not been fully studied. Employing X-ray crystallography and computational studies, we report the spatial and electronic consequences of replacing an amide with the triazole in analogues of cystic fibrosis drugs in the VX-770 and VX-809 series. Crystallographic analyses quantify subtle differences in the relative positions and conformational preferences of the R1 and R2 substituents attached to the amide and triazole bioisosteres. Computational studies derived from the X-ray data highlight the improved hydrogen bonding donor and acceptor capabilities of the amide in comparison to the triazole. This analysis of the spatial and electronic differences between the amide and 1,2,3-triazole will inform medicinal chemists as they consider using the triazole as an amide bioisostere.

Unravelling the interactions between biomedical thermoresponsive polymer and biocompatible ionic liquids

Studies on the phase behavior of thermoresponsive polymers (TRPs) in the presence of ionic liquids (ILs) are an emerging area for the preparation and design of new polymeric materials. The search to understand the influence of ILs on polymers has come into the limelight as a great challenge. Hitherto, limited work on the phase transition behavior of TRPs in the presence of ILs is available. In this work, we studied the phase behavior of poly-N-isopropylacrylamide (PNIPAM) in presence of cholinium chloride ([Ch]Cl), cholinium acetate ([Ch][Ac]), cholinium bitartrate ([Ch][Bit]) and cholinium dihydrogen citrate ([Ch][DHCit]) using various techniques such as UV–Visible absorption spectroscopy, steady-state fluorescence spectroscopy, thermal fluorescence spectroscopy, viscosity (ƞ) and dynamic light scattering (DLS). All cholinium-based ILs studied show qualitatively and quantitatively a similar phase behavior, suggesting it to be quite resilient with respect to changes in the anion of the ILs. However, concentration and orientation of ILs have a varied effect on the phase transition temperature and on the aggregation behavior of PNIPAM. Our temperature dependent experimental results explicitly signifies that lower critical solution temperature (LCST) values decrease with increasing the temperature and concentration of studied ILs, which indicates that hydrophobic interactions are dominating. Anions of IL with their charge densities, hydration capacities and hydration energies leads to the hydrophobicity of PNIPAM + IL aqueous solution. High polarity, owing to the charge of the carboxylate groups in [Ch][DHCit] and [Ch][Bit], and hydrogen bond acceptor capability of the Cl− anion causes their affinity for water inducing ability. This is the first report on the influence of cholinium-based ILs on the phase behavior of the PNIPAM. The current research work provides significant information on the phase transition and aggregation behavior of TRPs in ILs, which paves the way for potential applications in various fields.

Development of Fullerene Thin-Film Assemblies and Fullerene-Diamine Adducts towards Practical Nanocarbon-Based Electronic Materials

Abstract Fullerenes are attractive spherical aromatic molecules with good electron acceptor capabilities and good utility as an n-type organic semiconductor. By using a fullerene-amine addition reaction, it was possible to fabricate ultrathin-film assemblies of fullerene on the surface of substrates, which were confirmed by photoelectric conversion applications. Addition reactions between fullerenes and primary aliphatic diamines can also occur to form insoluble adduct particles consisting of fullerenes and diamines. In one example, C60-ethylenediamine adduct particles can be solubilized by addition of alkylacid chloride to residual amino groups of the adducts. Spin-coated or dip-coated thin-films of C60-ethylenediamine adducts from their solutions are useful as n-type organic semiconductors which was confirmed with solar cell application. In this account, the history of the fabrication and application of fullerene thin-film assemblies and fullerene-diamine adducts using the fullerene-amine addition reaction is introduced and summarized from the early studies to more recent developments.

Photophysical properties of bichromophoric Fe(II) complexes bearing an aromatic electron acceptor

The replacement of heavy metals used by industry to produce optical devices would considerably reduce the environmental and economic cost of man-made technology. A possible strategy relies on the employment of lighter and more abundant metals like iron. The exploitability of the photophysics of Fe(II) complexes is, however, generally limited by their short excited-state lifetimes and poor emission properties. The present work studies the impact of appending an electron acceptor (anthracene) to N-heterocyclic carbene (NHC) iron complexes with the aim to trap the excited-state energy and, therefore, delay the excited-state decay of the considered iron compounds. Hence, the photophysical properties of six prototypes (built with different spacers between the NHC ligand and the anthracene moieties) have been studied by using time-dependent density functional theory and by determining the natural transition orbitals of the excited states. The computational results suggest that ethynyl bridges induce dual absorption properties, covering red and infrared wavelengths in addition to the violet–blue absorption of the metal-to-ligand charge transfer band, already reported for the parent compound. The nature of the lowest lying triplet states indicates that, for all the considered prototypes, the excitation involves π* orbitals localized over anthracene, confirming its electron acceptor capabilities and suggesting a possible equilibrium between different excited states that might lead to enhanced excited-state lifetimes and/or boosted luminescence properties.

Dissolution of cotton cellulose in 1:1 mixtures of 1-butyl-3-methylimidazolium methylphosphonate and 1-alkylimidazole co-solvents

During the past decade, ionic liquids (ILs) have attracted increasing attention as efficient, novel solvents for dissolving cellulose. In this study, 1-butyl-3-methylimdazolium methylphosphonate ([C4C1im][(OMe)(H)PO2]) was used in the dissolution of cotton cellulose and the role of 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, and 1-butylimidazole as co-solvents was investigated. The progress of the dissolution was monitored using polarized light microscopy (PLM) and the regenerated cellulose was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The effect of 1-alkylimidazoles as co-solvents in cellulose dissolution was examined in terms of the basicity (hydrogen-bond acceptor capability), conductivity, viscosity, and ionicity of the IL and IL/co-solvent mixtures. These studies showed that the addition of 1-alkylimidazole co-solvents enhances cellulose dissolution by the IL and that the role of these co-solvents is mainly to increase mass transport by reducing the viscosity of the mixtures.

Effect of peptidic backbone on the nucleic acid dimeric strands

This study explores the effect of N-(2-aminoethyl)-glycine peptide chain incorporated at the backbone of nucleic acid dimeric strands on the basis of reactivity descriptors. The structures of obtained PNA dimeric strands were examined through backbone (α, β, γ, δ, ε and ω) and linker (χ1, χ2 and χ3) torsions. The calculated torsions were found to coincide well the available experimental and theoretical data. The peptidic chain incorporated nucleic acid dimers show a drastic change in global reactivity descriptor (gr) values. The vertical ionisation potential (VIP) and polarizability (α′) of peptide chain incorporated Guanine constructs are found to be higher by about 0.24 eV and 98.49 Å3 than their natural counterparts. The obtained gr along with frontier molecular orbitals depict G-containing dimeric strands to have efficient donor and acceptor capability with improved sensitivity upon peptide chain inclusion. This study in general could serve as a basic tool to understand the reactivity properties of PNA modularities, which are the possible building blocks of extended nanostructures.