Polar Solvents Research Articles

Exploring optimal cathode composite design for high-performance all-solid-state batteries

All-solid-state batteries (ASSBs) have attracted considerable attention due to their high stability, offering a safer alternative to currently used batteries. Extensive research has been conducted to improve cathode part performance. However, the conventional hand mixing (HM) process results in inhomogeneous particle distribution, causing poor interparticle contact due to uneven stress distribution, and the solution process causes unwanted solid electrolyte (SE) deterioration when using a polar solvent although it ensures uniform SE distribution. To overcome these limitations, based on the design rule considering SE surface coverage of less than 100 %, we propose a cathode/SE composite, showing decent ionic/electronic conductivities, uniform SE distribution, and intimate interparticle contact, achievable through a mass-producible mechanical mixing (MM) process. Unlike the HM cell, the MM cell forms well-defined ionic percolating pathways and shows excellent structural stability. Consequently, the MM cell exhibits improved capacity retention during 1000 cycles and stable cyclability even under the harsh condition of 7 wt% SE. Finite element analysis theoretically demonstrates that uniform electrode and electrolyte currents are responsible for the improved performances including increased cathode utilization efficiency and reduced overpotentials. This study reveals the importance of composite design and uniform SE distribution in developing high-performance ASSBs at a practical cell level.

Unraveling the effect of molecular medium on the fluorosolvatochromism of the biphenyl- salicylate derivative drug Diflunisal: Experimental and computational study

Understanding the photochemical behavior of a photosensitive drug through its molecular properties is crucial for assessing potential phototoxicity. In this study, we examine how the molecular microenvironment influences the physicochemical and photochemical properties of Diflunisal (DIF), an organofluorine salicylate derivative drug. To elucidate the photophysical properties of DIF, we employed absorption and fluorescence spectroscopy techniques combined with various DFT-based computational methods. The solvatochromic and fluorescence behaviors of DIF were investigated employing various neat solvents of various polarity and hydrogen bonding (HB) capabilities. The molecular behavior of DIF exhibited mixed fluorosolvatochromism, where a negative fluorosolvatochromism is noted as solvent polarity increases, where DIF exhibited positive fluorosolvatochromism within the examined set of protic polar solvents. These fluorosolvatochromic behaviors suggest that a combination of factors, including solvent polarity, hydrogen bonding capacity, and specific solvation effects, influences the fluorosolvatochromic properties of DIF. To elucidate the impact of specific and non-specific interactions between DIF and solvent on the fluorosolvatochromism of DIF, we utilized Catalán’s four empirical scales model. The results revealed that the solvent’s acidity, basicity, and polarizability had approximately equivalent and notable impacts on the fluorosolvatochromic behavior of DIF. For a molecular-level explanation of the experimental spectral properties, we employed DFT and TD-DFT/B3LYP/6–31 + G(d) computational methods, incorporating the IEFPCM implicit solvation approach. It is also revealed that the negative fluorosolvatochromism of DIF is attributed to the solvent’s impact on the main electronic transition, namely HOMO → LUMO. It is revealed as well that not only the salicylate moiety is affected by the solvent, but also the biphenyl moiety can exhibit a major contribution to the observed behavior. The results presented here offer insights into the photochemical behavior of DIF within various microenvironments at the molecular level. This understanding could inform future endeavors aimed at mitigating induced toxicity and side effects of DIF.

Effects of extraction solvents on antarctic krill oil quality characteristics and some insights into the oxidation stability of antarctic krill oil

The effects of 6 solvent combinations (Folch, acetone/ethanol [1:1, v/v], ethanol [95%, v/v], n-hexane/ethyl acetate [7:3, v/v], n-hexane/ethanol [10:1, v/v], and isopropanol alcohol [95%, v/v] with different polarities on the quality characteristics of Antarctic krill oil (AKO) extracted from Antarctic krill were investigated in this study. The relationship between endogenous active substances and oxidative stability was also explored. There was a significant positive correlation between solvent polarity and AKO yield (r = 0.91, p < 0.05), a significant positive correlation with total tocopherols (r = 0.84, p < 0.05) and a weak correlation with astaxanthin (r = 0.53). In addition, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in AKO were mostly located in phosphatidylcholines, lysophosphatidylcholine, phosphatidylethanolamine and lysophosphatidylethanolamine. ethanol (95%, v/v) had the highest efficiency of glycerophospholipids (34.39%), EPA (20.83%) and DHA (9.61%). For liposolubility trace substances, astaxanthin were extracted most efficiently with Folch (283.49 μg/g) and acetone/ethanol (1:1, v/v, 264.58 μg/g), whereas tocopherols were extracted most efficiently with ethanol (95%, v/v, 114.29 μg/g). Astaxanthin, tocopherol and phosphatidylcholines were closely related to the oxidative stability of AKO. Astaxanthin in AKO showed a significant (p < 0.05) positive correlation with ABTS· scavenging capacity, whereas tocopherol and phosphatidylcholines showed a significant (p < 0.05) dose-effect relationship with total reducing power.

Synthesis and Molecular Dynamic Simulation of Novel Cationic and Non-cationic Pyrimidine Derivatives as Potential G-quadruplex-ligands.

Drug resistance has been a problem in cancer chemotherapy, which often causes shortterm effectiveness. Further, the literature indicates that telomere G-quadruplex could be a promising anti-cancer target. We synthesized and characterized two new pyrimidine derivatives as ligands for G-quadruplex DNA. The interaction of novel non-cationic and cationic pyrimidine derivatives (3a, b) with G-quadruplex DNA (1k8p and 3qsc) was explored by circular dichroism (CD) and ultraviolet-visible spectroscopy and polyacrylamide gel electrophoresis (PAGE) methods. The antiproliferative activity of desired compounds was evaluated by the MTT assay. Apoptosis induction was assessed by Propidium iodide (P.I.) staining and flow cytometry. Computational molecular modeling (CMM) and molecular dynamics simulation (MD) were studied on the complexes of 1k8p and 3qsc with the compounds. The van der Waals, electrostatic, polar solvation, solventaccessible surface area (SASA), and binding energies were calculated and analyzed. The experimental results confirmed that both compounds 3a and 3b interacted with 1k8p and 3qsc and exerted cytotoxic and proapoptotic effects on cancer cells. The number of hydrogen bonds and the RMSD values increased in the presence of the ligands, indicating stronger binding and suggesting increased structural dynamics. The electrostatic contribution to binding energy was higher for the cationic pyrimidine 3b, indicating more negative binding energies. Both experimental and MD results confirmed that 3b was more prone to form a complex with DNA G-quadruplex (1k8p and 3qsc), inhibit cell growth, and induce apoptosis, compared to the non-cationic pyrimidine 3a.

Application of Abraham's solvation parameter model to extractables and leachables studies in pharmaceutical and medical device industries: A tutorial

The Abraham's solvation parameter model is an important tool to model and predict distribution properties of compounds in numerous partitioning systems in chemistry, environmental chemistry, medicine, and biology. The evaluation of the distribution properties in extractables and leachables (E&L) studies in pharmaceutical and medical device industries is another major application of this model. This tutorial is aimed at illustrating the applications of the model in E&L studies. Specific examples of the application illustrated in this tutorial include: (a) establishment of equivalent or similar solvents; (b) determination of polarity of solvents, biological tissues, and materials; (c) development of drug product simulating solvents; (d) understanding solvent extraction power for a material; (e) selection of solvent and standards in pretreatment of extraction samples; and (f) chromatography retention prediction for E&L.

Chemical composition of organic extracts of Phyla nodiflora L. in Syria by GC-MS

IntroductionPhyla nodiflora L. is a perennial herbaceous plant belonging to the Verbenaceae family. It is widely used as an herbal drink to treat many diseases. It has antioxidant, antifungal and anti-inflammatory properties. In traditional medicine, it is used to treat skin infections. However, there is little information on the chemical composition of organic plant extracts. Therefore, the aim of this study was to determine the chemical composition of organic extracts of P. nodiflora L. MethodsIn this study, organic extracts were prepared using a continuous Soxhlet extractor and four different solvents with increasing polarity from nonpolar to polar solvents (petroleum ether, chloroform, ethyl acetate, and isopropanol) to ensure the possibility of extracting a wide range of compounds. GC‒MS analysis was performed to determine the chemical constituents of the organic extracts. ResultsNineteen compounds were identified in the petroleum ether (Et) extract, 14 in the chloroform (Ch) extract, 18 in the ethyl acetate (Ea) extract and 15 in the isopropanol (Is) extract. The most important compounds in the Et extract were 1,1-diethoxyethane (33.9 %) and nonadecane (19.9 %). The most important compound in the Ch extract was octacosane (37.4 %). The most important compounds in the Ea extract were 3-hydroxy-dodecanoic acid (17.7 %) and geranyl isovalerate (15.5 %). The most important compound in the Is extract was behenic acid alcohol (18.6 %). The chemical structures of the major compounds were confirmed by mass spectrometry by studying their fragmentation mechanism and comparing the molecular weights of the resulting fragments with the molecular weights of the peaks present in each mass spectrum. ConclusionsThe results of this study show that the dominant compounds in nonpolar extracts (petroleum ether and chloroform) are hydrocarbons, ethers, epoxides, and silicon compounds, while the dominant compounds in moderately polar extracts (ethyl acetate and isopropanol) are alcohols, carbonyl compounds, and oxygenated terpenes.

Synthesis, optical properties, DNA, β-cyclodextrin interactions, and antioxidant evaluation of novel isoxazolidine derivative (ISoXD2): A multispectral and computational analysis

ISoXD2 are well explored among versatile and outstanding class of pharmacophores for the preparation and discovery of drugs. Herein, the electronic absorption and emission spectra of ISoXD2 were investigated in three different solvents. The observed transition was attributed to π-π* with charge transfer character. Changes in the excited state and shift of the absorption and emission peaks to longer wavelengths are observed as a result of increasing solvent polarity, due to the interactions between the ISoXD2 molecule and the solvent molecules surrounding it. Changing the solvent confirms its solvatochromic effect. UV–vis and fluorescence analysis revealed that ISoXD2 binds to deoxyribonucleic acid (DNA) by intercalation mode, with a stoichiometric ratio of 1:1.5. Moreover, the fluorescence intensity of DNA bound to ethidium bromide (EB) in the presence of ISoXD2 was investigated. From this analysis, the Stern-Volmer quenching constant (Ksv), quenching rate constant (kq), binding constant (Kb) and binding sites number (n) were found to be 5.654 × 103 M−1, 2.827 × 1011 M−1 s−1, 3.81 × 104 M−1 and 1.225, respectively. The interaction between ISoXD2 and β-CD was investigated through absorption spectra analysis. Kb for this interaction was determined to be 4.9 × 104 M−1. The free radical-scavenging ability of the prepared ISoXD2, examined by DPPH and ABTS assays have shown a good antioxidant activity. Furthermore, modeling study was conducted to explore their plausible binding mechanism with ISoXD2 and to support the experimental results.

Synthesis of Intrinsically-Fluorescent Aliphatic Tautomeric Polymers for Proton-Conductivity, Dual-State Emission, and Sensing/Oxidation-Reduction of Metal Ions.

Herein, fluorescent conducting tautomeric polymers (FCTPs) are developed by polymerizing 2-methylprop-2-enoic acid (MPEA), methyl-2-methylpropenoate (MMP), N-(propan-2-yl)prop-2-enamide (PPE), and in situ-anchored 3-(N-(propan-2-yl)prop-2-enamido)-2-methylpropanoic acid (PPEMPA). Among as-synthesized FCTPs, the most promising characteristics in FCTP3 are confirmed by NMR and Fourier transform infrared (FTIR) spectroscopies, luminescence enhancements, and computational studies. In FCTP3, ─C(═O)NH─, -C(═O)N<, ─C(═O)OH, and ─C(═O)OCH3 subluminophores are identified by theoretical calculations and experimental analyses. These subluminophores facilitate redox characteristics, solid state emissions, aggregation-enhanced emissions (AEEs), excited-state intramolecular proton transfer (ESIPT), and conductivities in FCTP3. The ESIPT-associated dual emission/AEEs of FCTP3 are elucidated by time correlated single photon counting (TCSPC) investigation, solvent polarity effects, concentration-dependent emissions, dynamic light scattering (DLS) measurements, field emission scanning electron microscopy images, and computational calculations. The cyclic voltammetry measurements of FCTP3 indicate cumulative redox efficacy of ─C(═O)OH, ─C(═O)NH─/-C(═O)N<, ─C(─O─)═NH+─/─C(─O─)═N+, and ─C(═N)OH functionalities. In FCTP3, ESIPT-associated dual-emission enable in the selective detection of Cr(III)/Cu(II) at λem1/λem2 with the limit of detection of 0.0343/0.079 ppb. The preferential interaction of Cr(III)/Cu(II) with FCTP3 (amide)/FCTP3 (imidol) and oxidation/reduction of Cr(III)/Cu(II) to Cr(VI)/Cu(I) are further supported by NMR-titration; FTIR and X-ray photoelectron spectroscopy analyses; TCSPC/electrochemical/DLS measurement; alongside theoretical calculations. The proton conductivity of FCTP3 is explored by electrochemical impedance spectroscopy and I-V measurements.

Fumaronitrile-based π–conjugated mechanochromic material: Design, synthesis and photophysical properties

In this study, we synthesized four 2,3-bis(4-methoxyphenyl)fumaronitrile-based D–A–D quadrupoles using a two-fold Suzuki-Miyara cross-coupling reaction and conducted comprehensive investigations into their photophysical properties, including absorption, fluorescence, and lifetime in the solution state. All compounds demonstrate a blue to green light emission both in solution and thin films, alongside moderate quantum yields and lifetimes (in the nanosecond range) in solution state, while also presenting significant spectral shifts in thin films. Aggregation-induced emission (AIE) behavior in THF/water mixtures and solvatochromic effects were observed by varying the solvent polarities. The energy levels of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were examined via density functional theory (DFT) calculations. Intriguingly, mechanical force application, such as grinding, induced a red shift in the photoluminescence spectra, while exposure to dichloromethane fumes resulted in reversible spectra changes. These distinct behaviors underscore the mechanochromic nature of the compounds, as corroborated by both photoluminescence and powder-XRD analyses. Importantly, these unique characteristics render the compounds suitable for applications in inkless pens and rewritable printers.

Antioxidant and antibacterial activity of nutgrass tuber (Cyperus rotundus L.) on extraction with different solvent polarity and particle sizes

Nutgrass tuber (Cyperus rotundus L.) is a wild weed often used as traditional medicine locally, having potential as an antioxidant and antibacterial. This study aimed to determine the effect of the type of solvent with different polarity and particle size on the antioxidant and antibacterial activity of nutgrass tuber (C. rotundus L.) extract and to determine the best type of solvent and particle size to produce nutgrass tuber extract with the highest antioxidant activity and antibacterial activity. The experiment design was a factorial randomized block design (RBD). A total of three different solvent treatments (ethanol, ethyl acetate and n-hexane) was the first factor while the particle size with three treatment levels of 40-, 60-, and 80-mesh sieves was the second factor. Data were then analyzed by analysis of variance (ANOVA) followed by Tukey's test. The results showed that the type of solvent, particle size, and their interactions were highly significant on the antioxidant activity and the antibacterial activity against Staphylococcus aureus, while the antibacterial activity against Escherichia coli had a significant effect by the interaction. For the antioxidant activity test, the best treatment was ethanol with particle size produced using the 80-mesh sieve resulting in an IC50 value of 192.18±0.43 ppm. The best antibacterial activity was the extract using ethyl acetate and the particle size produced using the 80-mesh sieve. Meanwhile, the antibacterial activity against E. coli and S. aureus was 3.53±0.19 mm2 /mL and 10.67±0.14 mm2 /mL (AU), respectively. This suggested nutgrass tuber extract with suitable solvent has the potency as an antioxidant and antibacterial.

A FTIR Evident-Based Exploration of the Antioxidant Activity of Five Threatened Cactus Species

Cacti, members of the botanical family Cactaceae, comprise approximately 127 genera and approximately 1,850 known species within the Caryophyllales order. Presently, various anthropogenic activities are causing the endangerment of several cactus species. Among the reasons cited for this threat, the aesthetic and medicinal values of cacti have garnered notable attention. This study aims to explore the medicinal potential, particularly in terms of antimicrobial, antioxidant, and phytochemical properties, of five threatened cactus species listed by the International Union for Conservation of Nature (IUCN) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES): Micranthocereus estevesii, Euphorbia lactea, Haageocereus crestata, Ferocactus acanthodes and Mammillaria huitzilopochtli. A Fourier-transform infrared (FTIR) analysis was conducted to substantiate and corroborate the findings. Notably, no prior studies have investigated the medicinal properties of these five species, underscoring the novelty of our research. Initially, specimens of the five cacti were collected from the Regional Plant Resource Center, Bhubaneswar, air-dried, and milled into powder. Phytoconstituents were then extracted individually using polar (water) and non-polar (methanol) solvents. The antimicrobial properties were assessed using agar well diffusion assays against Candida albicans, Escherichia coli and Staphylococcus aureus. Results indicated that methanol extracts of Micranthocereus estevesii and Euphorbia lactea inhibited Candida albicans, while aqueous extracts of Micranthocereus estevesii and Ferocactus acanthodes inhibited Escherichia coli and Staphylococcus aureus. Methanol extracts exhibited superior antioxidant activity compared to aqueous extracts. FTIR spectroscopy revealed distinctive peak values representing various functional groups in the extract components, including alcohols, carboxylic acids, phenols, aldehydes, alkanes, alkenes, ketones, aromatics, aliphatic amines, primary amines, ethers, alkyl halides, and esters. Both aqueous and methanolic extracts demonstrated promising antibacterial efficacy among the five cactus species studied, suggesting their potential application in pharmaceuticals and medication development. However, habitat degradation and illegal commerce pose significant threats to these species, emphasizing the urgent need for conservation efforts.

ISOLATION OF ETHYL TRANS-P-METHOXYCINNAMATE FROM Kaempferia galanga L. RHIZOMES BY USING N-HEXANE

Kaempferia galanga L. rhizomes contain ethyl trans-p-methoxycinnamate as a major secondary metabolite compound and biomarker. Various extraction methods with different solvents can isolate ethyl trans-p-methoxycinnamate with potential bioactivities. This paper reported the isolation of ethyl trans-p-methoxycinnamate from two varieties of K. galanga L. rhizomes by maceration in n-hexane. The small and large varieties of K. galanga samples produced ethyl trans-p-methoxycinnamate in 1.43% and 1.84% yields, higher than other methods and polar solvents of previous research. Structural elucidation of the obtained ethyl trans-p-methoxycinnamate was performed by FTIR, MS, and 1H NMR spectroscopies.

Transient Covalent Polymers through Carbodiimide‐Driven Assembly

AbstractBiochemical systems make use of out‐of‐equilibrium polymers generated under kinetic control. Inspired by these systems, many abiotic supramolecular polymers driven by chemical fuel reactions have been reported. Conversely, polymers based on transient covalent bonds have received little attention, even though they have the potential to complement supramolecular systems by generating transient structures based on stronger bonds and by offering a straightforward tuning of reaction kinetics. In this study, we show that simple aqueous dicarboxylic acids give poly(anhydrides) when treated with the carbodiimide EDC. Transient covalent polymers with molecular weights exceeding 15,000 are generated which then decompose over the course of hours to weeks. Disassembly kinetics can be controlled using simple substituent effects in the monomer design. The impact of solvent polarity, carbodiimide concentration, temperature, pyridine concentration, and monomer concentration on polymer properties and lifetimes has been investigated. The results reveal substantial control over polymer assembly and disassembly kinetics, highlighting the potential for fine‐tuned kinetic control in nonequilibrium polymerization systems.

Transient Covalent Polymers through Carbodiimide-Driven Assembly.

Biochemical systems make use of out-of-equilibrium polymers generated under kinetic control. Inspired by these systems, many abiotic supramolecular polymers driven by chemical fuel reactions have been reported. Conversely, polymers based on transient covalent bonds have received little attention, even though they have the potential to complement supramolecular systems by generating transient structures based on stronger bonds and by offering a straightforward tuning of reaction kinetics. In this study, we show that simple aqueous dicarboxylic acids give poly(anhydrides) when treated with the carbodiimide EDC. Transient covalent polymers with molecular weights exceeding 15,000 are generated which then decompose over the course of hours to weeks. Disassembly kinetics can be controlled using simple substituent effects in the monomer design. The impact of solvent polarity, carbodiimide concentration, temperature, pyridine concentration, and monomer concentration on polymer properties and lifetimes has been investigated. The results reveal substantial control over polymer assembly and disassembly kinetics, highlighting the potential for fine-tuned kinetic control in nonequilibrium polymerization systems.

Evaluation and optimisation of phenolic compounds extracted by supercritical carbon dioxide from the seeds of Plantago ovata and their comparison with conventional extraction

This study’s main objectives are to evaluate and confirm the effects of the extraction process, operating conditions, solvent type and solvent polarity on the yield and quality of the extracts. Supercritical carbon dioxide (scCO2) and Soxhlet were specially used in this study to extract bioactive chemicals from the seeds of a natural plant known as Plantago ovata. No studies have been published so far regarding the extraction from the seeds of this plant using scCO2.The effects of three operating parameters (pressure, temperature and particle size) on the extraction yield, total phenolic content, total flavonoid content (TFC), total tannin content (TTC) and antioxidant activity were assessed in this study using the Box–Behnken statistical experimental design (BBD). The chemical components in the extracts were separated and identified using gas chromatography mass spectrometry. According to the antioxidant activity results, scCO2 failed to produce bioactive compounds with interesting properties when operated within operating range conditions.

Enhanced aggregation induced emission by H-bond between the barbiturate molecules containing hydroxyl group

Barbiturates had been widely studied as a molecule with aggregation induced emission (AIE) phenomenon, but barbiturates as a group with multiple hydrogen bond donor and acceptor sites, the relationship between intermolecular hydrogen bond and AIE phenomenon has not been mainly studied. In this paper, a new barbiturate fluorescence molecule BNOH with hydroxyl group was designed and synthesized in order to analyze the relationship between hydrogen bond and molecular AIE phenomenon by increasing the functional group (–OH) that was easy to form hydrogen bond. By spectroscopic analysis, BNOH had structural torsion in aqueous mixed solution, which led to fluorescence decrease, while in aprotic mixed solvent, there was strong AIE phenomenon. DFT and TD-DFT calculations at the B3LYP/6-31G (d) were performed for a deeper understanding of optical transitions. In addition, in order to investigate the difference of its fluorescence phenomenon, two other barbiturate derivatives were synthesized and their spectra were compared with BNOH. The relationship between hydrogen bond and AIE phenomenon of barbiturates was proved, and the fluorescence mechanism of BNOH in organic solvent was proposed and determined. We believe that this study will not only increase the understanding of barbiturate AIE compounds, but also contribute to the study of the important role of hydrogen bonds in the fluorescence phenomenon of barbiturate AIE compounds.

An NIR Type I Photosensitizer Based on a Cyclometalated Ir(III)-Rhodamine Complex for a Photodynamic Antibacterial Effect toward Both Gram-Positive and Gram-Negative Bacteria.

Type I photosensitizers offer an advantage in photodynamic therapy (PDT) due to their diminished reliance on oxygen levels, thus circumventing the challenge of hypoxia commonly encountered in PDT. In this study, we present the synthesis and comprehensive characterization of a novel type I photosensitizer derived from a cyclometalated Ir(III)-rhodamine complex. Remarkably, the complex exhibits a shift in absorption and fluorescence, transitioning from "off" to "on" states in aprotic and protic solvents, respectively, contrary to initial expectations. Upon exposure to light, the complex demonstrates the effective generation of O2- and ·OH radicals via the type I mechanism. Additionally, it exhibits notable photodynamic antibacterial activity against both Gram-positive and Gram-negative bacteria, demonstrated through in vitro and in vivo experiments. This research offers valuable insights for the development of novel type I photosensitizers.

Computational insights into solvent polarity associated excited state behaviour for 2-(1H-benzoimidazol-2-yl)−5-diethylamino-phenyl fluorophore

Inspired by the mesmerising charm emanating from the precisely controlled attributes displayed by 2-(1H-benzoimidazol-2-yl)−5-diethylamino-phenyl (HDP) and its derivatives in the domains of photochemistry and photobiology, our present undertaking predominantly focuses on exploring the complexities of light-triggered excited state reactions for HDP fluorophore dissolved in solvents with diverse levels of polarity. Initially, we performed molecular structure optimisation at various stages of the proton transfer process and collected data on bond length, bond angle, and core-valence bifurcation (CVB) index for the molecular framework. Subsequently, infrared (IR) vibrational spectra were analysed to evaluate the reinforcement of hydrogen bonds in different solutions. Furthermore, the investigation of orbital transitions and potential energy curves has led to the conclusion that the ESIPT process of HDP molecules is most likely to occur in nonpolar ccl4 solution, followed by chloroform solution; acetonitrile ranks last. In essence, the nonpolar aprotic solvents are more conducive to facilitating the ESIPT process. This research aims to contribute towards advancements in new luminescent materials and prove valuable in display technology and medical imaging fields while also promoting related technological development.

Computational Studies of Reactions of 1,2,4,5-Tetrazines with Enamines in MeOH and HFIP.

The reaction between 1,2,4,5-tetrazines and alkenes in polar solvents proceeds through a Diels-Alder cycloaddition along the C-C axis (C3/C6 cycloaddition) of the tetrazine, followed by dinitrogen loss. By contrast, the reactions of 1,2,4,5-tetrazines with enamines in hexafluoroisopropanol (HFIP) give 1,2,4-triazine products stemming from a formal Diels-Alder addition across the N-N axis (N1/N4 cycloaddition). We explored the mechanism of this interesting solvent effect through DFT calculations in detail and revealed a novel reaction pathway characterized by C-N bond formation, deprotonation, and a 3,3-sigmatropic rearrangement. The participation of an HFIP molecule was found to be crucial to the N1/N4 selectivity over C3/C6 due to the more favored initial C-N bond formation than C-C bond formation.

Total synthesis of Comfreyn A and structural analogues via two photochemical key steps.

In this work the influence of o-fluorine substituents on the photo-dehydro-Diels-Alder (PDDA) reaction was investigated and the findings of this study were applied to the total synthesis of natural products. The reactant molecules consisted of two alkyl arylpropiolates, connected by a suberic acid tether and bearing fluorine substituents in each of the o-positions. While quantum chemical calculations suggested that a fluorine substituent prevents an attack of the adjacent carbon atom in the second C-C bond forming step of the PDDA reaction, this attack took place nevertheless. The subsequent fluoride elimination, assisted by protic solvents or trialkylsilanes, resulted in an "Umpolung" of the 4-position of the cycloallene intermediate enabling the introduction of nucleophiles at this position. The nucleophilic replacement of the second fluorine substituent could also be triggered photochemically. After removal of the tether, the two arene moieties stand nearly perpendicular to each other and a selective excitation of the naphthalene moiety was possible. This led to an intramolecular photoinduced electron transfer (PET) followed by a nucleophilic replacement of the fluoride according to a SR+N1Ar* mechanism. The formed phenolic hydroxyl group underwent spontaneous lactonization with the adjacent ester group. Based on these results, the first total synthesis of the lignan Comfreyn A and some structural analogues were developed.