Polar Solvents Research Articles

Dual-Channel Imine-Amine Photoisomerization in a Benzoimidazole and Benzothiazole Coupled System: Photophysics and Applications.

A molecule, namely 2-(1H-benzo[d]imidazol-2-yl)-6-(benzo[d]thiazol-2-yl)-4-bromophenol (BIBTB), having a two-way proton transfer unit of thiazole and imidazole moieties was synthesized and characterized by NMR, electrospray ionization mass spectrometry (ESI-MS), and single-crystal diffraction studies. Steady state and time-resolved spectral studies of BIBTB support excited state intramolecular proton transfer (ESIPT), causing imine-amine tautomerization through a two-way 6-membered H-bonded ring, where the N atoms of benzothiazole and the benzoimidazole unit are involved as proton acceptor sites. Interestingly, in a nonpolar and moderately polar solvent, photoisomerization in BIBTB is found to be favored toward the thiazole ring, whereas in a highly polar solvent, it is favored toward the imidazole ring. A spectral comparison of BIBTB with judicially designed molecules 2-(benzo[d]thiazol-2-yl)-4-bromophenol (HBT) and 2-(1H-benzo[d]imidazol-2-yl)-4-bromophenol (BIB) supports these inferences. Theoretical calculation using the Density Functional Theory (DFT) at CAM-B3LYP/6-311+G(d,p) level supports the existence of two low-energy 6-membered hydrogen-bonded planar conformers in the ground state in the gas phase and in solvents of different dielectrics. The potential energy curves (PECs) calculated along the proton transfer (PT) coordinate are found to have a high energy barrier in the ground state and to be barrierless or have a low energy barrier in the excited state for both the forms. The calculated vertical excitation and the emission energy from the relaxed excited and PT states show good correlation with the experimental spectral data. Aggregation of BIBTB in water with red shifted emission was established from X-ray single-crystal structure analysis, solid state emission, and Dynamic Light Scattering (DLS) measurement. The molecule BIBTB also acts as a fluorescence probe for sensing the explosive picric acid in the subnano scale and can be used to determine the proportion of water in dimethyl sulfoxide (DMSO) solvent.

Tetracene Diacid Aggregates for Directing Energy Flow toward Triplet Pairs.

A comprehensive investigation of the solution-phase photophysics of tetracene bis-carboxylic acid [5,12-tetracenepropiolic acid (Tc-DA)] and its related methyl ester [5,12-tetracenepropynoate (Tc-DE)], a non-hydrogen-bonding counterpart, reveals the role of the carboxylic acid moiety in driving molecular aggregation and concomitant excited-state behavior. Low-concentration solutions of Tc-DA exhibit similar properties to the popular 5,12-bis((triisopropylsilyl)ethynl)tetracene, but as the concentration increases, evidence for aggregates that form excimers and a new mixed-state species with charge-transfer (CT) and correlated triplet pair (TT) character is revealed by transient absorption and fluorescence experiments. Aggregates of Tc-DA evolve further with concentration toward an additional phase that is dominated by the mixed CT/TT state which is the only state present in Tc-DE aggregates and can be modulated with the solvent polarity. Computational modeling finds that cofacial arrangement of Tc-DA and Tc-DE subunits is the most stable aggregate structure and this agrees with results from 1H NMR spectroscopy. The calculated spectra of these cofacial dimers replicate the observed broadening in ground-state absorption as well as accurately predict the formation of a near-UV transition associated with a CT between molecular subunits that is unique to the specific aggregate structure. Taken together, the results suggest that the hydrogen bonding between Tc-DA molecules and the associated disruption of hydrogen bonding with solvent produce a regime of dimer-like behavior, absent in Tc-DE, that favors excimers rather than CT/TT mixed states. The control of aggregate size and structure using distinct functional groups, solute concentration, and solvent in tetracene promises new avenues for its use in light-harvesting schemes.

Highly dispersed biochar as a sustainable filler for enhancing mechanical performance and biodegradation of polybutylene succinate

AbstractSustainability has become increasingly important as environmental issues continue to rise. Biodegradable polymers offer a sustainable solution as they use biomass. In this study, biochar (BC) prepared by the pyrolysis of biomass was compounded with polybutylene succinate (PBS) to enhance its Young's modulus, and the residual BC was shown to amend the soil, following degradation. The incorporation of biochar into the PBS matrix is strategically achieved through a BC with treatment involving an aprotic polar solvent. This process not only reduces the size of the biochar particles but also ensures their uniform dispersion within the PBS matrix. As a result, a remarkable 2.5‐fold increase in Young's modulus is observed, reaching an impressive 571.04 MPa, compared with the baseline Young's modulus of neat PBS, which stands at 220.92 MPa. Interestingly, the degradation rate of the resulting composites was comparable to that of neat PBS despite the decrease in the number of potential hydrolysis sites owing to the increased Young's modulus of the PBS/BC composite. These sustainable composite exhibited properties different from those of conventional PBS and is expected to be used in potentially novel applications toward environmental sustainability, such as in agricultural mulch films or electronic printing.

GCMS-based phytochemical profiling and in vitro pharmacological activities of plant Alangium salviifolium (L.f) Wang

BackgroundThere is an urge for traditional herbal remedies as an alternative to modern medicine in treating several diseases. A significant number of modern pharmaceutical drugs are based on or derived from medicinal plants or their extracts. These drugs derived from the plant origin have various antimicrobial, antioxidant, anticancer, anti-inflammatory activities. Alangium salviifolium belongs to Cornaceae family and is well known for its medicinal properties. The present study was carried out to evaluate the antibacterial, antioxidant effect and possible bioactive components present in the chloroform, acetone, ethanol, methanol and aqueous extract of Alangium salviifolium leaves.MethodologyDried leaves of Alangium salviifolium were subjected to serial solvent extraction using increasing polarity of solvents, i.e., chloroform, acetone, methanol, ethanol, and distilled water. Crude extracts were further tested for qualitative analysis of phytochemicals using standard procedure, while GCMS analysis was performed to identify the probable phytocompounds. Antibacterial activity was performed against bacterial pathogens using agar well method, whereas antioxidant activity was performed using in vitro PM, DPPH and FRAP assays.ResultsPhytochemical analysis of the extracts revealed the presence of key phytochemical classes. Using gas chromatography-mass spectrometry, several high and low molecular weight chemical compound kinds were discovered. These chemical substances are regarded as having significant biological and pharmacological effects. All crude extracts had considerable and comparable in vitro antioxidant and antibacterial properties.ConclusionsAccording to the findings of this study, Alangium salviifolium leaves are a rich source of phytoconstituents that are crucial in stopping the advancement of numerous disorders.

4,4-Difluoroproline as a Unique 19F NMR Probe of Proline Conformation.

Despite the importance of proline conformational equilibria (trans versus cis amide and exo versus endo ring pucker) on protein structure and function, there is a lack of convenient ways to probe proline conformation. 4,4-Difluoroproline (Dfp) was identified to be a sensitive 19F NMR-based probe of proline conformational biases and cis-trans isomerism. Within model compounds and disordered peptides, the diastereotopic fluorines of Dfp exhibit similar chemical shifts (ΔδFF = 0-3 ppm) when a trans X-Dfp amide bond is present. In contrast, the diastereotopic fluorines exhibit a large (ΔδFF = 5-12 ppm) difference in chemical shift in a cis X-Dfp prolyl amide bond. DFT calculations, X-ray crystallography, and solid-state NMR spectroscopy indicated that ΔδFF directly reports on the relative preference of one proline ring pucker over the other: a fluorine which is pseudo-axial (i.e., the pro-4R-F in an exo ring pucker, or the pro-4S-F in an endo ring pucker) is downfield, while a fluorine which is pseudo-equatorial (i.e., pro-4S-F when exo, or pro-4R-F when endo) is upfield. Thus, when a proline is disordered (a mixture of exo and endo ring puckers, as at trans-Pro in peptides in water), it exhibits a small Δδ. In contrast, when the Pro is ordered (i.e., when one ring pucker is strongly preferred, as in cis-Pro amide bonds, where the endo ring pucker is strongly favored), a large Δδ is observed. Dfp can be used to identify inherent induced order in peptides and to quantify proline cis-trans isomerism. Using Dfp, we discovered that the stable polyproline II helix (PPII) formed in the denatured state (8 M urea) exhibits essentially equal populations of the exo and endo proline ring puckers. In addition, the data with Dfp suggested the specific stabilization of PPII by water over other polar solvents. These data strongly support the importance of carbonyl solvation and n → π* interactions for the stabilization of PPII. Dfp was also employed to quantify proline cis-trans isomerism as a function of phosphorylation and the R406W mutation in peptides derived from the intrinsically disordered protein tau. Dfp is minimally sterically disruptive and can be incorporated in expressed proteins, suggesting its broad application in understanding proline cis-trans isomerization, protein folding, and local order in intrinsically disordered proteins.

Synthesis and Structure of Protonated Sulfur Dioxide

AbstractSalts of protonated sulfur dioxide were synthesized by recrystallization of [FS(OX)2][SbF6] (X=H, D) in aprotic solvents at low temperatures. Hemiprotonated sulfur dioxide [(SO2)2H][Sb2F11] was obtained from the solvent SO2 and the monoprotonated sulfur dioxide [OSOD][Sb2F11], using 1,1,1,2‐tetrafluoroethane as solvent. For both compounds, single crystals were obtained and an X‐ray structure analysis was conducted. Furthermore, the salts were characterized by Raman spectroscopy and the results were discussed together with quantum chemical calculations on the M06‐2X/aug‐cc‐pVTZ level of theory.

Synthesis and Structure of Protonated Sulfur Dioxide.

Salts of protonated sulfur dioxide were synthesized by recrystallization of [FS(OX)2][SbF6] (X=H, D) in aprotic solvents at low temperatures. Hemiprotonated sulfur dioxide [(SO2)2H][Sb2F11] was obtained from the solvent SO2 and the monoprotonated sulfur dioxide [OSOD][Sb2F11], using 1,1,1,2-tetrafluoroethane as solvent. For both compounds, single crystals were obtained and an X-ray structure analysis was conducted. Furthermore, the salts were characterized by Raman spectroscopy and the results were discussed together with quantum chemical calculations on the M06-2X/aug-cc-pVTZ level of theory.

Photophysical Properties of Sinapic Acid and Ferulic Acid and Their Binding Mechanism with Caffeine.

Sinapic acid (SA) and ferulic acid (FA) are bioactive compounds used in the food, pharmaceutical, and cosmetic industries due to their antioxidant properties. In this work, we studied the photophysical properties of SA and FA in different solvents and concentrations and their interactions with caffeine (CF), using ultraviolet-visible (UV-Vis), fluorescence spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The findings show that the quantum yield, fluorescence lifetime, radiative decay rates, and non-radiative decay rates of SA and FA are influenced by the concentrations and solvent polarity. The interaction between SA and FA with CF was also studied using UV-Vis and fluorescence spectroscopy. The results indicate that the CF quenched the fluorescence intensity of SA and FA by static quenching due to the formation of a non-fluorescent complex. The van't Hoff equation suggests that the van der Waals forces and hydrogen bonds force were responsible for the interaction between SA and CF, as indicated by a negative change in enthalpy ( < 0) and a negative change in entropy ( < 0). On the other hand, the interaction between FA and CF was primarily controlled by electrostatic force, as indicated by a negative change in enthalpy ( < 0) and a positive change in entropy ( > 0). The negative change in Gibbs free energy ( ) indicates that both compounds underwent a spontaneous binding process.

Solvent Replacement Strategies for Processing Pharmaceuticals and Bio-Related Compounds—A Review

An overview of solvent replacement strategies shows that there is great progress in green chemistry for replacing hazardous di-polar aprotic solvents, such as N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), and 1,4-dioxane (DI), used in processing active industrial ingredients (APIs). In synthetic chemistry, alcohols, carbonates, ethers, eucalyptol, glycols, furans, ketones, cycloalkanones, lactones, pyrrolidinone or solvent mixtures, 2-methyl tetrahydrofuran in methanol, HCl in cyclopentyl methyl ether, or trifluoroacetic acid in propylene carbonate or surfactant water (no organic solvents) are suggested replacement solvents. For the replacement of dichloromethane (DCM) used in chromatography, ethyl acetate ethanol or 2-propanol in heptanes, with or without acetic acid or ammonium hydroxide additives, are suggested, along with methanol acetic acid in ethyl acetate or methyl tert-butyl ether, ethyl acetate in ethanol in cyclohexane, CO2-ethyl acetate, CO2-methanol, CO2-acetone, and CO2-isopropanol. Supercritical CO2 (scCO2) can be used to replace many organic solvents used in processing materials from natural sources. Vegetable, drupe, legume, and seed oils used as co-extractants (mixed with substrate before extraction) can be used to replace the typical organic co-solvents (ethanol, acetone) used in scCO2 extraction. Mixed solvents consisting of a hydrogen bond donor (HBD) solvent and a hydrogen bond acceptor (HBA) are not addressed in GSK or CHEM21 solvent replacement guides. Published data for 100 water-soluble and water-insoluble APIs in mono-solvents show polarity ranges appropriate for the processing of APIs with mixed solvents. When water is used, possible HBA candidate solvents are acetone, acetic acid, acetonitrile, ethanol, methanol, 2-methyl tetrahydrofuran, 2,2,5,5-tetramethyloxolane, dimethylisosorbide, Cyrene, Cygnet 0.0, or diformylxylose. When alcohol is used, possible HBA candidates are cyclopentanone, esters, lactone, eucalytol, MeSesamol, or diformylxylose. HBA—HBA mixed solvents, such as Cyrene—Cygnet 0.0, could provide interesting new combinations. Solubility parameters, Reichardt polarity, Kamlet—Taft parameters, and linear solvation energy relationships provide practical ways for identifying mixed solvents applicable to API systems.

Evaluation of antimicrobial activity and bioactive compound analysis of Verbascum thapsus L. A folklore medicinal plant

BackgroundThe prevalence of microbial infectious diseases is a major contributor to morbidity and mortality on a global scale due to the emergence of antibiotic-resistant microbes, despite the fact that many new antibiotics have been introduced for several decades. In present scenario, the potential utilization of natural plant derived extracts for medicinal and therapeutic purposes has increased remarkably due to adverse effects of synthetic drugs and resistance among pathogenic microbes. Aim of the studyVerbascum thapsus L. (Common mullein) has been traditionally used as a medicine for lung, skin and throat and many other disorders since time immemorial, therefore, the current study was aimed to evaluate the antimicrobial activity of leaf and root extracts of Verbascum thapsus against pathogenic bacterial and fungal strains and its phytochemical composition by spectral studies. MethodsSoxhlet extraction method was employed for extraction process by using varying polarity solvents like hexane, ethyl acetate and methanol. Phytochemical analysis of methanol extract was determined by Fourier Transform-Infrared Spectroscopy (FTIR) and Gas Chromatography-Mass Spectrometry (GC–MS). Antimicrobial activity was evaluated by determining the MIC and MBC/MFC of each extract by broth dilution method. ResultsThe antimicrobial competence of each extract sample was evaluated against six pathogenic bacterial strains and three fungal strains. Methanolic extract of leaves and the ethyl acetate extract of roots of Verbascum thapsus exhibited significant zones of inhibition against all the tested microorganisms. The highest inhibition zone was observed against the bacterial strain Bacillus subtilis (24.1±0.18 mm) followed by Streptococcus pyogenes (22.9±0.64 mm) and the fungal strain Aspergillus niger (22.8±0.55 mm) at a concentration of 500 μg/ml. Methanolic leaf extract strongly inhibited the growth of tested microbial strains with MIC ranged from 15.625 to 125 μg/ml. The FTIR and GCMS analysis confirms the presence of bioactive compound, possessing broad range of therapeutic activities. ConclusionThis Presence of various important phytoconstituents and broad-spectrum antimicrobial activity points Verbascum thapsus as a promising source for the isolations of molecules responsible for antimicrobial activities.

Spring Lock: Constructing Cluster Emitters with Colorful TADF from Non‐Conjugated Polymaleimide Helical Chains

AbstractNon‐conjugated luminescent polymers have received much attention due to their excellent flexibility, processability, and biocompatibility. However, the single emission color and low solid‐state luminescence efficiency restrict their further development. Herein, by introducing carboxyl‐terminated alkyl chains on the rigid and helical polymaleimide backbone, a series of non‐conjugated luminescent polymers are designed and synthesized. Due to the “spring lock” formed by the synergism of scalable helical main chains and flexible alkyl side chains, these polymers exhibit effective cluster luminescence with thermally activated delayed fluorescence (TADF) property, thereby significantly improving the solid‐state luminescence efficiency with the quantum yield up to 59.6%. The TADF emission wavelengths of the polymer powders can be tuned from 498 to 639 nm through changing reaction solvents, because the conformation of helical chains forming clusters is sensitive to solvent polarity. Interestingly, metal ions can induce the polymers to construct self‐repairing cluster luminescence gels, which show excellent potential applications in ammonia detection and information encryption. This work not only provides an effective design strategy for the colorful cluster luminescence with high‐efficiency TADF, but also further reveals the cluster luminescence mechanism and enlightens the promising applications of cluster luminescent gels.

Antioxidant proficiency in Serbian mushrooms: a comparative study on Hydnum repandum L. 1753 from mycorrhizal and edible niches

This study aimed to evaluate the antioxidant potential of autochthonous Hydnum repandum through LC-MS/MS profiling, total phenolic content (TP), total protein content (TPR), and antioxidant capabilities (DPPH, ABTS, and FRAP assays) across various extracts (CHCl3, acetone, 70% EtOH, 80% MeOH, and hot water). LC-MS/MS analysis revealed a predominant presence of quinic acid in polar solvents (ranging from 531.37 to 676.07 ng/mL), while EtOH and MeOH extracts exhibited elevated total phenolic levels (27.44 ± 0.32 and 28.29 ± 3.62 mg GAE/g d.w., respectively). Impressively, H. repandum showcased remarkable antioxidant properties, as evidenced by its FRAP values (57.29 to 199.96 mg AAE/g d.w.), ABTS values (5.69 to 29.95 mg TE/g d.w.), and IC50 values in the DPPH assay (91.40 to 372.55 μg/mL), which exhibited a strong correlation with TP. Notably, the acetone extract exhibited the most robust antioxidant activity where the highest TPR was observed, suggesting synergism of primary and secondary metabolites.

Robust Thiazole-Linked Covalent Organic Frameworks for Water Sensing with High Selectivity and Sensitivity.

The rational design of covalent organic frameworks (COFs) with hydrochromic properties is of significant value because of the facile and rapid detection of water in diverse fields. In this report, we present a thiazole-linked COF (TZ-COF-6) sensor with a large surface area, ultrahigh stability, and excellent crystallinity. The sensor was synthesized through a simple three-component reaction involving amine, aldehyde, and sulfur. The thiazole and methoxy groups confer strong basicity to TZ-COF-6 at the nitrogen sites, making them easily protonated reversibly by water. Therefore, TZ-COF-6 displayed color change visible to the naked eye from yellow to red when protonated, along with a red shift in absorption in the ultraviolet-visible diffuse reflectance spectra (UV-vis DRS) when exposed to water. Importantly, the water-sensing process was not affected by polar organic solvents, demonstrating greater selectivity and sensitivity compared to other COF sensors. Therefore, TZ-COF-6 was used to detect trace amounts of water in organic solvents. In strong polar solvents, such as N,N-dimethyl formamide (DMF) and ethanol (EtOH), the limit of detection (LOD) for water was as low as 0.06% and 0.53%, respectively. Even after 8 months of storage and 15 cycles, TZ-COF-6 retained its original crystallinity and detection efficiency, displaying high stability and excellent cycle performance.

Do Electrostatics Control the Diffusive Dynamics of Solitary Water? NMR and MD Studies of Water Translation and Rotation in Dipolar and Ionic Solvents.

NMR-based measurements of the diffusion coefficients and rotation times of solitary water and benzene at 300 K are reported in a diverse collection of 13 conventional organic solvents and 10 imidazolium ionic liquids. Proton chemical shifts of water are found to be correlated to water OH-stretching frequencies, confirming the importance of electrostatic interactions in these shifts. However, the influence of magnetic interactions in aromatic solvents renders chemical shifts a less reliable indicator of electrostatics. Diffusion coefficients (DB) and rotational correlation times (τB) of benzene in the solvents examined are accurately described as functions of viscosity (η) by DB ∝ η-0.81 and τB ∝ η0.64. Literature values of DB and τB in alkane and normal alcohols, which were not included among the solvents studied here, are systematically faster than predicted by these correlations, indicating that factors beyond solvent viscosity play a role in determining the friction on benzene. In contrast to benzene, water diffusion and rotation are poorly described in terms of viscosity alone, even in the dipolar and ionic solvents measured here. The present data and the substantial literature data already available on dilute water diffusion show a systematic dependence of DW on solvent polarity among isoviscous solvents. The aspect of solvent polarity most relevant to water dynamics is the ability of a solvent to accept hydrogen bonds from water, as conveniently quantified by the frequency of water's OH stretching band, ΔνOH. The friction on translation, ζtr = kBT/DW, and rotation, ζrot = kBTτW, are both well correlated by functions of the form ζ(η, ΔνOH) = a1ηa2 exp (a3ΔνOH), where the ai are adjustable parameters. Molecular dynamics simulations reveal a strong coupling between electrostatic and nonelectrostatic water-solvent interactions, which makes it impossible to dissect the friction on water into additive dielectric and hydrodynamic components. Simulations also provide a tentative explanation for the unusual form of the correlating function ζ(η, ΔνOH), at least in the case of ζrot.

Isolation and Characterization of a Triterpenoid Compound from Sodhita &lt;i&gt;Semecarpus anacardium&lt;/i&gt; L. Drupe Ethanolic Extract and its Anticancer Potential &lt;i&gt;In Vitro&lt;/i&gt;

Semecarpus anacardium is listed in Schedule E1 of the Drugs and Cosmetics Act, of 1940. It is purified (sodhana) and used in traditional medicine to treat various diseases, including gulma (hard mass/cystic growth or lump). Studies on Semecarpus anacardium in Non-Small Cell Lung Cancer (NSCLC) cell lines are hitherto unavailable, hence this study was conducted. The drupes of sodhita Semecarpus anacardium were extracted with solvents of different polarity, and the half-maximal inhibitory concentration (IC50) of each extract was determined in the NSCLC cell line (A549). The ethanolic extract with an IC50 of 47.09±0.032 μg/ml was found to be better than the other extracts and, therefore subjected to compound isolation by wet-pack column chromatography. The fractions (6-9 and 15-19) with a single spot identified by thin-layer chromatography were crystallized (56 mg) and used for spectral techniques. The probable compound structure of C30H50O2, elucidated by FTIR, 1H and 13C NMR revealed it as a triterpenoid derivative. The IC50 of the isolated compound was 15.73±0.019 μg/ml which was further used to investigate anti-cancer properties The treated cells showed apoptotic features like cell blebbing, loss of cell adhesion and membrane integrity. A semi-fragmented piece of unresolved DNA and G2/M phase arrest was observed in the treated cells. RT-qPCR analysis revealed that the expression of the NSCLC biomarkers c-ROS oncogene-1 (ROS1) and proinflammatory factor nuclear factor kappa B (NF-κB) was significantly (p&lt;0.05) downregulated in the treated cells. Based on these observations, it was concluded that the isolated compound could be a potential candidate for lung cancer therapy.

Controlling Anti-Penetration Performance by Post-Grafting of Fluorinated Alkyl Chains onto Polystyrene-block-poly(vinyl methyl siloxane).

Polydimethylsiloxane (PDMS) has been widely used as a surface coating material, which has been reported to possess dynamic omniphobicity to a wide range of both polar and nonpolar solvents due to its high segmental flexibility and mobility. However, such high flexibility and mobility also enable penetration of small molecules into PDMS coatings, which alter the chemical and physical properties of the coating layers. To improve the anti-penetration properties of PDMS, a series of fluorinated alkyl segments are grafted to a diblock copolymer of polystyrene-block-poly(vinyl methyl siloxane) (PS-b-PVMS) using thiol-ene click reactions. This article reports the chemical characterization of these model fluorosilicone block copolymers and uses fluorescence measurements to investigate the dye penetration characteristics of polymer thin films. The introduction of longer fluorinated alkyl chains can gradually increase the anti-penetration properties as the time to reach the maximum fluorescence intensity (tpeak) gradually increases from 11 s of PS-b-PVMS to more than 1000 s of PS-b-P(n-C6F13-VMS). The improvement of anti-penetration properties is attributed to stronger inter-/intrachain interactions, phase segregation of ordered fluorinated side chains, and enhanced hydrophobicity caused by the grafting of fluorinated alkyl chains.

Investigation of the Degradation of LiPF6- in Polar Solvents through Deep Potential Molecular Dynamics.

The nonaqueous electrolyte based on lithium hexafluorophosphate (LiPF6) is the dominant liquid electrolyte in lithium-ion batteries (LIBs). However, trace protic impurities, including H3O+, alcohols, and hydrofluoric acid (HF), can trigger a series of side reactions that lead to rapid capacity fading in high energy density LIBs. It is worth noting that this degradation process is highly dependent on the polarity of the solvents. In this work, a deep potential (DP) model is trained with a certain commercial electrolyte formula through a machine learning method. H3O+ is anchored with polar solvents, making it difficult to approach the PF6-, and suppressing the degradation process quickly at room temperature. Control experiments and simulations at different temperatures or concentrations are also performed to verify it. This work proposes a precise model to describe the solvation structure quantitatively and offers a new perspective on the degradation mechanism of PF6- in polar solvents.

Modulating the ESIPT Mechanism and Luminescence Characteristics of Two Reversible Fluorescent Probes by Solvent Polarity: A Novel Perspective.

As reversible fluorescent probes, HTP-1 and HTP-2 have favourable applications for the detection of Zn2+ and H2S. Herein, the impact of solvent on the excited-state intramolecular proton transfer (ESIPT) of HTP-1 and HTP-2 was comprehensively investigated. The obtained geometric parameters and infrared (IR) vibrational analysis associated with the intramolecular hydrogen bond (IHB) indicated that the strength of IHB for HTP-1 was weakened in the excited state. Moreover, structural torsion and almost no ICT behaviour indicated that the ESIPT process did not occur in HTP-1. Nevertheless, when the 7-nitro-1,2,3-benzoxadiazole (NBD) group replaced the H atom, the IHB strength of HTP-2 was enhanced after photoexcitation, which inhibited the twisting of tetraphenylethylene, thereby opening the ESIPT channel. Notably, hole-electron analysis and frontier molecular orbitals revealed that the charge decoupling effect was the reason for the fluorescence quenching of HTP-2. Furthermore, the potential energy curves (PECs) revealed that HTP-2 was more inclined to the ESIPT process in polar solvents than in nonpolar solvents. With a decrease in solvent polarity, it was more conducive to the ESIPT process. Our study systematically presents the ESIPT process and different detection mechanisms of the two reversible probe molecules regulated by solvent polarity, providing new insights into the design and development of novel fluorescent probes.

Synthesis of Naphthalimide Azocarboxylates Showing Turn-On Fluorescence by Substitution Reaction with Sulfinates.

The synthesis and characterization of sulfinate addition-responsive fluorescent molecules are described. We found that addition reaction of sulfinates to naphthalimide-substituted azocarboxylates afforded the corresponding sulfonyl hydrazides with high fluorescence quantum yields (up to 0.91 in THF and 0.54 in methanol), which exhibited a large Stokes shift (105 nm) in protic methanol solvent, while the unsubstituted hydrazide and the sulfonyl-position isomer showed no fluorescence in polar solvents.

Methyl‐ and Methoxy‐substituted 2‐(Pyridin‐2‐yl)‐4‐(4‐aminophenyl)quinazolines: Synthesis and Photophysical Properties

A series of 2‐(2‐pyridyl)quinazoline luminophores containing donor aryl fragment at position 4 and methyl or methoxy groups at benzene ring has been synthesized by efficient three‐step route. The linear optical properties have been studied by UV/Vis absorption and photoluminescence spectra in two solvents. We revealed that introduction of additional methyl group or the replacement of methyl substituents with methoxy ones lead to sequentially shift of absorption and emission maximum to blue region. 9H‐Carbazol‐9‐yl‐containing derivative is characterized by hypsochromically shifted absorption band compared to NEt2 and NPh2 counterparts. Unlike 9H‐carbazol‐9‐yl‐derivative, Et2N‐ and Ph2N‐bearing quinazolines demonstrate considerable decrease in quantum yield values when going from toluene to MeCN. Solvatochromic properties have been explored, the pronounced bathochromic shift was observed in fluorescence spectra with the increase of solvents polarity. Moreover, the compounds show significant shift of emission band with the increase of water fraction in DMSO/H2O mixture. Two‐photon optical properties were also studied, the two‐photon absorption cross‐sections in MeCN and toluene reached 120 GM and 210 GM, respectively. The presence of additional methyl group has little impact on δTPA, while introduction of methoxy substituents dramatically decreases TPA cross sections. Additionally, a quantum‐chemical calculations of synthesized compounds were performed to support the experimental data.