Effect Of Solvent Polarity Research Articles

Synthesis of furan-2-ones and spiro[furan-2,3ʹ-indoline] derivatives using polyether sulfone sulfamic acid catalysis

Polyether sulfone sulfamic acid (PES-NHSO3H) was prepared by simple sulfonation of a modified polyether sulfone. The number of acidic sites (SO3H) was determined to be 4.23 mmol H+/g by acid-base titration and 4.29 mmol H+/g by barium sulfate test. PES-NHSO3H was used as an efficient acidic catalytic system for the preparation of functionalized furan-2-ones and 2ʹ,5-dioxo-5 H-spiro[furan-2,3 ʹ -indoline]-3-carboxylate derivatives via the three-component reaction of anilines, aldehydes/1-ethylindoline-2,3-dione, and diethyl acetylene dicarboxylate in high yields (85–97%). The effect of polar and non-polar solvents on the productivity of the reaction was investigated. The catalyst was recovered 11 times without losses in catalytic potential.

The Stability Challenge of Furanic Platform Chemicals in Acidic and Basic Conditions.

The transition toward renewable resources is pivotal for the sustainability of the chemical industry, making the exploration of biobased furanic platform chemicals derived from plant biomass of paramount importance. These compounds, promising alternatives to petroleum-derived aromatics, face challenges in terms of stability under synthetic conditions, limiting their practical application in the fuel, chemical, and pharmaceutical sectors. Our study presents a comprehensive evaluation of the stability of furan derivatives in various solvents and under different conditions, addressing the significant challenge of their instability. Through systematic experiments involving GC‒MS, NMR, FT‒IR and SEM analyses, we identified key degradation pathways and conditions that either promote stability or lead to undesirable degradation products. These findings demonstrate the strong stabilizing effect of polar aprotic solvents, especially DMF, and reveal the dependence of furan stability on solvent and additive type. This research opens new avenues in the utilization of renewable furans by providing critical insights into their behavior under synthetic conditions, significantly impacting the development of sustainable materials and processes. The broad appeal of this study lies in its potential to guide the selection of conditions for the efficient and sustainable synthesis of furan-based chemicals, marking a significant advance in green chemistry and materials science.

Effect of solvent polarity on yield extract, antioxidant and antibacterial activities of phytochemicals from Andrographis paniculata leaves

ABSTRACT In this study, the impact of solvent polarity on the extraction yield, antibacterial activity and antioxidant characteristics of phytochemical compounds derived from Andrographis paniculata leaves was investigated. The simplicia of A. paniculata was macerated in different organic solvents with raising polarity (n-Hexane, ethyl acetate, dichloromethane, ethanol, methanol, methanol–water) at room temperature for 24 h. Preliminary screening revealed that the yield extract, phytochemical composition, antibacterial activity and antioxidant properties were influenced by the polarity of the solvent used for extraction. The optimum yield extract was obtained using a methanol–water solvent (50:50, v/v) of 15.46%. The most active antibacterial activity against biofilm-forming bacteria (Pseudomonas aeruginosa) was obtained using ethyl acetate and dichloromethane with a minimum inhibition concentration (MIC) value of 312.5 µg mL−1. Meanwhile, the antioxidant properties of A. paniculata leaf extract with all solvents shows a very weak level. The antibacterial activity and antioxidant properties of A. paniculata leaf extracts are related to the phytochemical content in the extract. This result is evident in the extract with ethyl acetate solvents with the highest total phenolic and flavonoid values. However, GC-MS analysis of A. paniculata extract revealed 20 components, with Supraene having the greatest compounds.

A density functional theory study of a series of symmetric dibenzylideneacetone analogues as potential chemical UV-filters

The aim of this research was to provide valuable insights on symmetrical α,β-unsaturated ketones as potential chemical ultraviolet (UV) filters from experimental data and theoretical aspects. Towards this end, density functional theory (DFT/B3LYP) calculations on a series of symmetrical α,β-unsaturated ketones, (1E,4E)-1,5-bis[4-(R)phenyl]penta-1,4-diene-3-one (R = methylthio, 1; R = dimethylamino, 2; R = ethyl, 3), were performed to determine the effect of different electron-donating substituents on their stability when exposed to solar UV radiation. Their molecular structures, and UV-visible, infrared (IR) and NMR (1H and 13C) spectra were theoretically obtained from their optimized geometries with the B3LYP/6-311++ G (d, p) basis set and were compared with the experimental results. Conformational analysis was performed and the most stable conformer of each compound was identified as the trans-trans conformer, which was further supported by experimental NMR data. The UV spectra and effect of solvent polarity and proticity were studied by the time-dependent-DFT (TD-DFT) approach with the B3LYP/6-311++G (d, p) level of theory. Furthermore, various molecular parameters like dipole moment, frontier molecular orbital (FMO) energies, ΔEHOMO-LUMO gap, lifetime of the first excited state (τ), global chemical reactivity descriptors, and natural bond orbital analysis were predicted at the same level of theory and compared with the experimental data. Inspection of the active FMOs revealed the photoinstability trends of 1 and 3 under UV irradiation. However, introducing a -N(CH3)2 substituent to 2 at the para-position improves its photostability towards simulated UV radiation. Thus, compound 2 has the potential to provide efficient broad-spectrum protection against UV radiation. This work has shown that molecular modelling strategies can assist to rationalize experimental findings and also support the identification of photoproducts of 1 and 3.

Synthesis and optimization of chitosan-incorporated semisynthetic polymer/α-Fe2O3 nanoparticle hybrid polymer to explore optimal efficacy of fluorescence resonance energy transfer/charge transfer for Co(II) and Ni(II) sensing

Initially, four synthetic fluorescent polymers (SFPs) are synthesized from α-methacrylic acid and methanolacrylamide monomers carrying –C(=O)OH and –C(=O)NH subfluorophores, respectively. Among SFPs, ∼1:1 incorporation of subfluorophores in the optimum SFP3 is explored by spectroscopic analyses. Subsequently, chitosan is incorporated in SFP3 to produce five semi-synthetic fluorescent polymers (SSFPs). The maximum incorporation of chitosan in SSFP4 is supported by different spectroscopies. In SSFP4, strong electrostatic interactions among polar functionalities of chitosan and synthetic polymer favor resonance-associated charge transfer (RCT) from SSFP4-(amide) to SSFP4-(canonical). Finally, three hybrid fluorescent polymers (HFPs) are fabricated encapsulating iron-oxide nanoparticle within SSFP4. The maximum proportion of hematite (α-Fe2O3) phase in HFPs is explored by spectroscopic, magnetometric, microscopic, and light scattering studies. HFP2 shows local/RCT/fluorescence resonance energy transfer (FRET) emission at 393/460/570 nm. In HFP2, FRET, RCT, and ratiometric pH-sensing within 3.0–6.5 phenomena are explored by solvent polarity effects, time-correlated single photon counting, quantum yield measurements, alongside I431/I460 vs pH plots. RCT and FRET emissions of HFP2 are utilized for selective sensing of Co(II)/Ni(II) with limits of detection of 4.990 ppb (460 nm)/4.353 ppb (570 nm) and 45.041 ppb (428 nm)/29.617 ppb (527 nm) in organic and aqueous solutions, respectively.

Theoretical Insight into the Fluorescence Spectral Tuning Mechanism: A Case Study of Flavin-Dependent Bacterial Luciferase.

Bioluminescence of bacteria is widely applied in biological imaging, environmental toxicant detection, and many other situations. Understanding the spectral tuning mechanism not only helps explain the diversity of colors observed in nature but also provides principles for bioengineering new color variants for practical applications. In this study, time-dependent density functional theory (TD-DFT) and quantum mechanics and molecular mechanics (QM/MM) calculations have been employed to understand the fluorescence spectral tuning mechanism of bacterial luciferase with a focus on the electrostatic effect. The spectrum can be tuned by both a homogeneous dielectric environment and oriented external electric fields (OEEFs). Increasing the solvent polarity leads to a redshift of the fluorescence emission maximum, λF, accompanied by a substantial increase in density. In contrast, applying an OEEF along the long axis of the isoalloxazine ring (X-axis) leads to a significant red- or blue-shift in λF, depending on the direction of the OEEF, yet with much smaller changes in intensity. The effect of polar solvents is directionless, and the red-shifts can be attributed to the larger dipole moment of the S1 state compared with that of the S0 state. However, the effect of OEEFs directly correlates with the difference dipole moment between the S1 and S0 states, which is directional and is determined by the charge redistribution upon deexcitation. Moreover, the electrostatic effect of bacterial luciferase is in line with the presence of an internal electric field (IEF) pointing in the negative X direction. Finally, the key residues that contribute to this IEF and strategies for modulating the spectrum through site-directed point mutations are discussed.

Copper and ZnO Dual-Catalyzed Photo-Assisted Depolymerization of Poly(Methyl Methacrylate) without Deoxygenation

Despite significant advancements in thermal and photothermal depolymerizations, the success of these techniques relies on tedious deoxygenation procedures. Herein, we report the development of the depolymerization technique efficient without prior deoxygenation, which was enabled by copper/ligand complexes and the inclusion (0.25 wt% relative to solvent) of zinc oxide (ZnO) nanocrystals activated by UV light. This approach was tested for poly(methyl methacrylate) (PMMA) prepared by atom transfer radical polymerization (ATRP); the effects of solvent polarity and the activity of ligands were investigated. Unexpectedly, a low-activity Cu-complex with 2,2‘-bipyridine ligand, in combination with a low-polarity solvent, 1,2,4-trichlorobenzene, enabled relatively high depolymerization yields in less than 1 h at 150 °C. Higher activity ATRP complexes with tris(2-pyridylmethyl)amine (TPMA) and N,N,N‘,N‘‘,N‘‘-pentamethyldiethylenetriamine (PMDETA) ligands, were less efficient, which was associated with their thermal decomposition and/or the excessive formation of radicals and premature termination of the chain ends. The presented facile approach was designed to be used even in partially aerated reactors, opening new avenues for efficient depolymerization.

First-principles study of solvent polarity effects in the Menshutkin reaction

Quaternary ammonium salts (QASs) have been used as antimicrobial agents, surfactants, and ionic liquids in electrical double-layer capacitors, rechargeable lithium-ion batteries, and dye-sensitized solar cells. It is well known that solvents and reactants strongly affect the Menshutkin reaction. However, QASs are potentially harmful to humans and the environment. To address these issues, we report the effects of solvent polarity on the thermochemistry of two selected Menshutkin reactions, (1) trimethylamine and 1-iodopropane yielded propyltrimethylammonium, and (2) methylacetamide and 1-iodopropane yielded acetylpropylmethylammonium. We systematically constructed possible QAS unique conformers within the first-principles framework in solvents that have three various polarities: toluene, acetonitrile, and water. The polar solvent shifted both reactions toward exergonic and decreased the Gibbs free activation energy. In addition, the polar solvent changed the favorable reaction for the acetylpropylmethylammonium formation only due to an intramolecular hydrogen bond. Therefore, we suggest that selecting high solvent polarity should be considered to address the potential health and environmental effect.

Solvent polarity effects on extraction yield, phenolic content, and antioxidant properties of Malvaceae family seeds: a comparative study

ABSTRACT The selection of appropriate solvents in the extraction process plays a crucial role in determining the nature and quantity of secondary metabolites extracted from medicinal plants. This study investigates the impact of solvent polarity on the extraction yield, phenolic content, and antioxidant properties of seeds from four plants belonging to the Malvaceae family: Abutilon fruticosum, Abutilon pannosum, Sida ovata and Malvastrum coromendelianum. The seed powder of each species was subjected to extraction using solvents with varying polarities, including acetone, chloroform, methanol, and water. Physicochemical analysis, extraction yield, quantitative phenolic content, and antioxidant activity were assessed. Total phenolic content (TPC) was determined using the Folin–Ciocalteu reagent, and antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Analysis of variance (ANOVA) revealed that the choice of extracting solvents significantly influenced (p < 0.05) extraction yield, phenolic content, and antioxidant properties. In conclusion, water and methanol emerged as the most effective solvents for achieving high extraction yields, phenolic compound content, and free radical scavenging activities. The results demonstrated a robust correlation between total phenolic content (mg of Gallic acid equivalent/g of sample) and free radical scavenging activity (IC50). The study highlights the substantial impact of solvent type, suggesting the potential benefits of using a combination of polar and nonpolar solvents to enhance the extraction efficiency of phytochemicals, phenolic content and antioxidant quality from medicinal plant seeds. Future investigations should focus on isolating and identifying active secondary metabolites from these extracts.

Substituent effects on first generation photochemical molecular motors probed by femtosecond stimulated Raman.

Unidirectional photochemical molecular motors can act as a power source for molecular machines. The motors operate by successive excited state isomerization and ground state helix inversion reactions, attaining unidirectionality from an interplay of steric strain and stereochemistry. Optimizing the yield of the excited state isomerization reaction is an important goal that requires detailed knowledge of excited state dynamics. Here, we investigate the effect of electron withdrawing and donating substituents on excited state structure and ultrafast dynamics in a series of newly synthesized first generation photochemical molecular motors. All substituents red-shift the absorption spectra, while some modify the Stokes shift and render the fluorescence quantum yield solvent polarity dependent. Raman spectra and density functional theory calculations reveal that the stretching mode of the C=C "axle" in the electronic ground state shows a small red-shift when conjugated with electron withdrawing substituents. Ultrafast fluorescence measurements reveal substituent and solvent polarity effects, with the excited state decay being accelerated by both polar solvent environment and electron withdrawing substituents. Excited state structural dynamics are investigated by fluorescence coherence spectroscopy and femtosecond stimulated Raman spectroscopy. The time resolved Raman measurements are shown to provide structural data specifically on the Franck-Condon excited state. The C=C localized modes have a different substituent dependence compared to the ground state, with the unsubstituted motor having the most red-shifted mode. Such measurements provide valuable new insights into pathways to optimize photochemical molecular motor performance, especially if they can be coupled with high-quality quantum molecular dynamics calculations.

A green plant-derived fluorescent polyphenol: Investigating the fluorescence properties of ellagic acid in diverse solvents

Ellagic acid (EA), a natural and environmentally friendly polyphenol, positively impacts human health and is widely used in the food and medical industries. It features a well-organized planar structure with an extensive sp2 carbon-conjugated area and four phenolic hydroxyl groups, making it favorable for light energy absorption and fluorescent emission. This positions EA as a promising candidate for advanced fluorescence applications. To date, the fluorescence properties of EA have not been thoroughly investigated. In this research, we comprehensively examined the fluorescence properties of EA in various solvents—including alkaline aqueous, alcoholic, nitrogenous, other organic solvents, and polyethylene glycols (PEGs)—using transient/steady-state fluorescence spectroscopy, ultraviolet–visible absorption spectroscopy, Fourier-transform infrared spectroscopy, and density functional theory calculations. Additionally, the relationship between structural changes of EA in these solvents and its fluorescence properties was deeply investigated. It was discovered that general solvation effects (solvent polarity effects), hydrogen bonding effects, and viscosity effects are the main ways that solvents alter the optical characteristics of EA. EA exhibits outstanding fluorescence characteristics in PEG400, creating a bright green fluorescence with the highest Stokes shift at 170 nm among the 32 organic solvents and alkaline aqueous solutions examined. This study is both foundational and essential, setting the stage for advancing the research on EA-based fluorescent materials in future endeavors.

Review on Synthesis of 2-(2-Hydroxyaryl) Benzothiazoles (HBT) for Excited-State Intra-molecular Proton Transfer (ESIPT)-Based Detection of Ions and Biomolecules.

In this review, we present a systematic and comprehensive summary of the recent developments in the synthetic strategies of 2-(2-hydroxyarylsubstituted)-benzothiazole (HBT) framework along with incorporation of various substituents on phenolic and benzothiazole rings which affect the emission process. The literature, spanning the years 2015-2024, on excited-state intramolecular proton transfer (ESIPT)-based studies of HBT derivatives comprising the effects of solvent polarity, substituents, and extended conjugation on fluorophores has been searched. ESIPT, intramolecular charge transfer, and aggregation-induced emissions enable these fluorescent probes to specifically interact with analytes, thereby altering their luminescence characteristics to achieve analyte detection. These fluorescent probes exhibit large Stokes shifts, high quantum yields, and excellent color transitions. Finally, the applications of HBTs as ESIPT-based fluorescent probes for the detection of cations, anions, and biomolecules have been summarized. We anticipate that this review will provide a comprehensive overview of the current state of research in this field and encourage researchers to develop novel ESIPT-based fluorophores with new applications.

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.

Computational Investigation about the Effects of Solvent Polarity and Chalcogen Element Electronegativity on ESIPT Behaviors for the Et2N-Substituted Flavonoid.

Inspired by the outstanding nature of flavonoid derivatives in the fields of chemistry and medicine, in this work we mainly focus on exploring the photo-induced properties of the novel Et2N-substituted flavonoid (ENF) fluorophore theoretically. Considering the potential photo-induced properties in different solvents and the chalcogen atomic electronegativity-associated photoexcitation, by time-dependent density functional theory (TDDFT) methods we primarily explore the intramolecular hydrogen bonding interactions and photo-induced charge redistribution behaviors. Via comparing geometrical data and the infrared (IR) spectral shifts-associated hydroxy moiety of ENF, we confirm that the intramolecular hydrogen bond O-H···O should be enhanced with facilitating an excited-state intramolecular proton-transfer (ESIPT) reaction. Particularly, the charge reorganization around hydrogen bonding moieties further reveals the tendency of ESIPT behavior. Combined with the construction of the potential energy surface and the search for reaction transition states, we finally confirmed the solvent-polarity-regulated behaviors as well as the chalcogen elements' electronegativity-dependent ESIPT mechanisms for the ENF fluorophore. We sincerely wish our work could accelerate the further development and applications of flavonoid derivatives.

Radical scavenging activity of bromophenol analogs: analysis of kinetics and mechanisms.

This theoretical study explores the antioxidant activity of five bromophenol analogs, with a particular focus on their interaction with different solvent environments of varying polarities. Key findings include the correlation between increased solvent polarity and enhanced antioxidant activity of these analogs, comparable in some instances to ascorbic acid. Notably, compound 5, developed by our research team, demonstrates superior antioxidant activity in both lipid and aqueous solutions, surpassing that of ascorbic acid and other tested analogs. This research contributes to the understanding of bromophenol analogs, presenting the first known kinetic and chemical stability data such as rate constants, pKa values, and branching ratios for reactions with the methylperoxyl radical (CH3OO•). The computational analyses were conducted using the Gaussian 09 software suite at the M05-2X/6-31 + G(d) computational level. These analyses employed conventional transition state theory to account for various potential mechanisms and effects of solvent polarity on the antioxidant activities of bromophenol analogs. The study meticulously calculated enthalpy under standard conditions (298.15K and 1atm) with necessary thermodynamic corrections. Additionally, the Quantum Mechanics-based Test for Overall Radical Scavenging Activity (QMORSA) protocol guided the evaluation of radical scavenging activity, ensuring a comprehensive assessment of the antioxidant potential of the compounds.

Effects of temperature and solvent polarity on the thermodynamic and photophysical properties of ferulic acid using density functional theory (DFT)

Ferulic acid (FA) possesses diverse biological properties and is extensively utilized in pharmaceuticals, cosmetics, and the food industry due to its non-toxic nature. However, environmental factors such as temperature and solvent polarity play a significant role in influencing the thermodynamic and photophysical properties of drugs, particularly during the drug optimization and design phases. This study investigates the impact of temperature and solvent polarity on the thermodynamic and optical properties of FA using density functional theory (DFT) with the B3LYP functional approach and the 6-311++G(d, p) basis set under various solvent and gas conditions. Additionally, vertical UV-vis absorption and emission spectra of FA in different solvent polarities and gas phases were analyzed using time-dependent density-functional theory (TDDFT) with the B3LYP method and the 6-31++G(d, p) basis set. Applying Koopman's theory, the chemical activity of FA was assessed based on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) values. The findings indicate that an increase in temperature within the range of 100–1000 K leads to elevated enthalpy, heat capacity, and entropy due to molecular vibrational activity, resulting in FA degradation and instability. Furthermore, thermodynamic parameters, HOMO and LUMO values, and the chemical activity of FA were also influenced by different solvent polarities. The absorption and emission spectra of FA exhibited a red shift due to interactions with solvents and solutes. Overall, this study analyzed the significance of environmental factors such as temperature and solvent polarity in pharmaceutical design and optimization processes to enhance drug efficacy and stability.

Influence of Solvent Polarity on Phytochemicals, Antioxidants, and Antimicrobial Properties of Delphinium denudatum: A Medicinal Herb from Sainj Valley, Himachal Pradesh, India

Plants with medicinal properties play an important role in pharmaceutical industries for their disease prevention and treatment applications. Delphinium denudatum, commonly known as jadwar, is an important medicinal plant of the Himalayan region. Therefore, in the present study, the effect of solvent polarity (using seven different solvents i.e., methanol, ethanol, acetone, chloroform, ethyl acetate, hexane, and water separately) was estimated for its secondary metabolites production, antioxidants, and antimicrobial activities. Among the seven different extracting solvents used, the methanol extract of leaf rendered the highest phenolic content (80.52 mg GAE/g (dry weight (dw)). Acetone extracts for the shoot were found to be most efficient with the extraction of the highest flavonoid content (57.53 mg QE/g (dw) while the methanol extract of root rendered the highest tannin content 18.78 mg TAE/g (dw). Likewise, the methanol extract of the leaf showed the highest flavonol content 34.76 mg QE/g (dw). For antioxidant activity, the IC50 value for ABTS activity ranged from 35.15 to 103.08 µg/mL, and for DPPH activity it was 75.23 to 256.21 µg/mL. Further, all the plant parts i.e., leaf, shoot, and root, showed antimicrobial activity against Bacillus subtilis, Escherichia coli, and Serratia marcescens having MIC between 400 to 900 µg/mL. Among all the tested plant parts, polar solvent leaf extracts had higher antioxidant activity. Furthermore, phenols, flavonols, tannins, and ABTS activity from leaf, shoot, and root have shown a positive relation with solvent polarity. In all three plant parts; phenols, flavonols, and tannin positively correlate with antibacterial activity. The present study further revealed that the secondary metabolites in the leaf, shoot, and root extracts of D. denudatum are an excellent source of antioxidant and antimicrobial activities, thus validating the species’ therapeutic potential.

Design, Synthesis, and Photophysical Properties of 5-Aminobiphenyl Substituted [1,2,4]Triazolo[4,3-c]- and [1,2,4]Triazolo[1,5-c]quinazolines.

Two series of novel [1,2,4]triazolo[4,3-c]- and [1,2,4]triazolo[1,5-c]quinazoline fluorophores with 4'-amino[1,1']-biphenyl residue at position 5 have been prepared via Pd-catalyzed cross-coupling Suzuki-Miyaura reactions. The treatment of 2-(4-bromophenyl)-4-hydrazinoquinazoline with orthoesters in solvent-free conditions or in absolute ethanol leads to the formation of [4,3-c]-annulated triazoloquinazolines, whereas [1,5-c] isomers are formed in acidic media as a result of Dimroth rearrangement. A 1D-NMR and 2D-NMR spectroscopy, as well as a single-crystal X-ray diffraction analysis, unambiguously confirmed the annelation type and determined the molecular structure of p-bromophenyl intermediates and target products. Photophysical properties of the target compounds were investigated in two solvents and in the solid state and compared with those of related 3-aryl-substituted [1,2,4]triazolo[4,3-c]quinazolines. The exclusion of the aryl fragment from the triazole ring has been revealed to improve fluorescence quantum yield in solution. Most of the synthesized structures show moderate to high quantum yields in solution. Additionally, the effect of solvent polarity on the absorption and emission spectra of fluorophores has been studied, and considerable fluorosolvatochromism has been stated. Moreover, electrochemical investigation and DFT calculations have been performed; their results are consistent with the experimental observation.

Photo-Physical Characteristics of Janus Green B in Different Solvents and its Interaction Mechanism with Silver Nanoparticles.

This work explores the effects of solvent polarity on Janus Green B (JGB) photophysical properties. The Lippert-Mataga, Billot, and Ravi equations were utilized to calculate the singlet-state excited dipole moments (µe) and ground state dipole moments (µg) using absorption and fluorescence spectra analyses. The results showed an increase in the former, which is suggestive of electronic structural alterations upon excitation. Analysis of fluorescence quantum yield values revealed that JGB's environment had an impact on its emission characteristics; it was particularly sensitive to silver nanoparticles, suggesting possible interactions. While simulations of electron density, electrostatic potential, and energy gap (Eg) helped to understand the electronic structure of JGB, theoretical absorption spectra produced by Time Dependent Density Function Theory (TD-DFT) calculations offered insights into electronic transitions during absorption. To sum up, the present study contributes to our comprehension of the molecular behavior of JGB in various solvents by elucidating the intricate relationship among solvent polarity, molecular environment, and interactions with silver nanoparticles. Additionally, theoretical computations support the interpretation of experimental results.

Effect of solvent polarity on secondary metabolite content and α-glucosidase enzyme IC50 of Dendrophthoe pentandra (L). Miq leaves extract

Effect of solvent polarity on secondary metabolite content and α-glucosidase enzyme IC50 of Dendrophthoe pentandra (L). Miq leaves extract