Journal of Chemical Sciences最新文献

The host-guest interactions of two macrocycles L₁ and L₂ with 8-aniline-1-naphthalene sulfonic acid (1,8-ANS) were evaluated by fluorescence emission spectra. It was found that 1,8-ANS had a quenching effect upon the addition of the two macrocycles, which contain both 2,6-pyridylamide and dipyrrole units, and the corresponding binding ratios were also obtained. Furthermore, the binding behavior was investigated by H NMR titration. The results show that both the binding ratios of L₁ and L₂ with 1,8-ANS molecule are 1:1, and the stability constants are 3.06×10⁴ L·mol^-1 and 6.58×10³ L·mol^-1, respectively.

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The host-guest interactions of macrocycles L₁ and L₂ with 8-aniline-1-naphthalene sulfonic acid were evaluated by fluorescence spectra and H NMR titration. The binding ratios of L₁ and L₂ with the compound are both 1:1, and the stability constants are 3.06×10⁴ L·mol^-1 and 6.58×10³ L·mol^-1.

This study deals with the preparation and corrosion inhibition investigations of pyrazoline-sulfonamide hybrid, namely 4-((3-methyl-5-oxo-4,5-dihydro-1H-pyrazol-4-yl)diazenyl) benzene sulfonamide 4. Elemental analysis, Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (¹H NMR), and ¹³CNMR spectra investigated the pyrazoline-sulfonamide structure. The mild steel corrosion inhibition was investigated in 1 M HCl and 3.5% NaCl solutions using various techniques, including electrochemical, gravimetric, and microscopic techniques. The inhibition efficiency was 95.4 and 87.7% at 500 ppm inhibitor in 1 M HCl and 3.5% NaCl, respectively. The positive values of ∆H_ads (44.184 and 31.403 kJ/mol, in 1 M HCl and 3.5% NaCl, respectively) indicate that inhibitor adsorption is an endothermic process. Moreover, the high values of K_ads (0.281 and 0.148 M^-1) indicate more significant adsorption and thus stronger inhibitory efficiency. Langmuir adsorption isotherm was used to evaluate mild steel corrosion inhibition by pyrazoline-sulfonamide. Experimental data agree with data obtained from B3LYP density functional theory calculations. Therefore, based on the experimental and theoretical data, pyrazoline-sulfonamide is recommended as a corrosion inhibitor of mild steel in aqueous media.

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Pyrazoline-sulfonamide (PS) has been prepared and used as novel corrosion inhibitors of mild steel. Langmuir adsorption isotherm was used to evaluate MS corrosion inhibition by PS. Experimental data are in good agreement with B3LYP DFT calculations. Therefore, PS is recommended as a corrosion inhibitor of mild steel in aqueous media.

Though metal complex-based redox couples showed promising results in test cell devices of dye-sensitized solar cells (DSSCs), it hampers the scale-up of modules/panels due to mass transport and recombination issues. Copper (II/I) redox couple-based DSSCs have dispensed exceptional results at diffused/artificial indoor light conditions as potential candidates for Internet of Things (IoT) applications. Recently, our group have reported triphenylimidazole based metal-free organic dyes (LG-P series) with [Cu(tmby)₂]^2+/+ (tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine) redox couple realizing device efficiency of ~10% under low-light conditions. In the present study, we extended the work using iodide-triiodide (I⁻/I₃⁻) redox couple with LG-P series of sensitizers and measured the device efficiencies under both full sun (100 mW/cm²) and low-light conditions (1000 lux indoor illumination). Under full sun condition, LG-P3 has delivered a power conversion efficiency (PCE) of 2.15%, whereas at 1000 lux daylight, LED LG-P1 showed a PCE of 10.53%, and at 1000 lux daylight CFL LG-P3 showed PCE of 9.19%, which we observed with I⁻/I₃⁻ redox electrolyte. We have adopted charge extraction (CE), open-circuit voltage decay (OCVD) and electrochemical impedance spectroscopy (EIS) to explain the efficiency differences in LG-P series of dyes.

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Mass transport and recombination are two hurdles for metal complex-based redox couples for dye-sensitized solar cells. We have fabricated DSSC devices using triphenylimidazole-based organic dyes with I⁻/I₃⁻ redox electrolyte and measured its device efficiency under full sun and artificial/indoor light conditions and the potential for the Internet of Things (IoT) applications.

Utilization of carbon materials having excellent selectivity and robustness can have tremendous influence in the field of membrane-based separation. Herein, a hybrid polysulfone multi-walled carbon nanotube Hollow Fiber (HF) membrane was fabricated for enantioseparation of β-substituted-α-amino acids. Thin Film Nanocomposite (TFN) membrane was prepared via interfacial polymerization between D-tryptophan with carboxylated multi-walled carbon nanotubes and trimesoylchloride. The enantioseparation performance of the membranes was demonstrated through sorption and permeation study. On passing a racemate solution through the cross-linked membranes, the D-tryptophan-linked chiral probe adsorbed the D-isomer of the racemate, and L-isomer was passed to permeate side through the membrane. In a nutshell, the thin film nanocomposite enacts as the effective layer over the HF membrane which ensured that the apportioned chiral selectors were adequate to attain 99% of enantioselectivity.

Graphical abstract

Hybrid nanocomposite membranes were prepared via interfacial polymerization between D- tryptophan with carboxylated multi-walled carbon nanotubes and trimesoyl chloride over polysulfone support. On passing a racemate solution of β-substituted-α-amino acids through the hybrid membranes, the chiral probe selectively adsorbed the D-isomer. The thin-film nanocomposite enacts as the effective layer over the hollow fiber membrane which ensures the apportioned chiral selectors were adequate to attain 99% of enantioselectivity.

A Schiff base fluorescent “turn-off” sensor L based on 2, 4-diamino-6-hydroxypyrimidine, and 2-hydroxy-1-naphthaldehyde was synthesized, which shows excellent selectivity and sensitivity towards Cu²⁺ ions in an aqueous medium. The detection limit of the probe was found to be 11.92 µM which is much lower than the acceptable level of Cu²⁺ ions in drinking water as set by the World Health Organization (30 µM) and the U. S. Environmental Protection Agency (20 µM). Furthermore, a 1: 0.5 binding stoichiometry between the probe and Cu²⁺ ion was confirmed from the fluorescence titration data, Job’s plot, and DFT calculation. The binding constant (K_a) of Cu²⁺ ion with the probe was found to be 6.3 × 10⁴ M⁻¹. Thus, the overall study reveals that the synthesized Schiff base ligand is a potential fluorescent sensor for Cu²⁺ions.

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The research study includes the synthesis of a novel and efficient Schiff base ligand L, which is highly sensitive and a selective fluorescent sensor for Cu²⁺ ions with a very low detection limit.

In order to find amide compounds with desired antifungal activity, 16 nicotinamide derivatives containing diphenylamine moieties were prepared by condensation of 2-chloronicotinic acid with substituted N¹-phenylbenzene-1,2-diamines based on the structure of fungicide boscalid. The structures of the synthesized compounds were characterized by ¹H NMR, ¹³C NMR, ESI-MS, and elemental analysis. Among the compounds screened, compound 3a had high inhibitory effects against Rhizoctonia solani in vitro and in vivo, which slightly exceeded boscalid. The study of the structure-activity relationship provides important information for further structural optimization. Molecular docking offered a reasonable explanation to guarantee its fungicidal activity against R. solani. These results could provide a benchmark for understanding the antifungal activity against the phytopathogenic fungus R. solani and prompt us to develop more potent fungicides.

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Sixteen nicotinamide derivatives containing diphenylamine moieties were prepared based on the structure of fungicide boscalid. Thereinto, compound 3a showed high antifungal activity against Rhizoctonia solani. Structure-activity relationship study provided important information for further structural optimization. Molecular docking offered a reasonable explanation to guarantee its fungicidal activity.

Five perovskite materials of the general formula La_1–xSr_xMn_1-yZn_yO₃ (x = 0, 1, 2, 3, and y = 0, 2) were successfully synthesized by the citric acid sol-gel route and characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunner-Emmet-Teller (BET) technique and X-ray photoelectron spectroscopy (XPS). The materials were employed as heterogeneous catalysts in the Hantzsch reaction, producing 1,4-dihydropyridine derivatives. Incorporating Zn into the parent perovskite LaMnO₃ improved the catalytic activity, which was greatly enhanced by the simultaneous introduction of Sr. In addition to the positive effect of Zn and Sr incorporation, the results also showed that the catalytic activity was related to the surface Mn⁴⁺ content and acidic character. The La_0.9Sr_0.1Mn_0.8Zn_0.2O₃ catalyst was recycled and reused four times after demonstrating significant catalytic activity in a polar protic solvent (ethanol). After four cycles of use, the catalyst did not exhibit a significant reduction in catalytic activity, despite the formation of some secondary phases revealed by XRD and XPS analyses.

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Zn and Sr doubly partial substitution in lanthanum manganite perovskite resulted in a high catalytic activity of the Hantzsch reaction. The results showed that the catalytic activity is related to the creation of oxygen vacancies and the defect associations, in addition to surface acidity and Mn⁴⁺ content

Graphene quantum dots (GQDs), a zero-dimensional material, are emerging as a potential fluorescent probe with a wide range of applications, particularly bio-imaging and optical sensing. In this work, we have fabricated the blue-emitting Graphene Quantum Dots (GQDs) and utilized as for free bilirubin (BR) detection. Under optimal conditions, the fluorescence of GQDs was quenched linearly with the successive addition of BR concentrations. The probe exhibited a wide linear range (40.53-237.55 μM), low detection limit (9 μM), high selectivity, and rapid response towards free BR. The drastic quenching in the fluorescence intensity of GQDs with the addition of BR is due to Förster Resonance Energy Transfer (FRET) between GQDs and bilirubin. The efficiency of energy transfer between GQD and BR was determined as 43%. Therefore, this free BR sensing platform using GQDs may prove useful in the diagnosis of jaundice. Our study opens up the possibility of designing a low-cost biosensor that will be suitable for a real sample study.

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Our study presents the fabrication of blue-emitting Graphene Quantum Dots (GQDs) and employs them as an assay to detect free bilirubin (BR). Fluorescence of GQDs was quenched linearly as BR concentrations increased from 40.53 to 237.55 μM and exhibited a low detection limit (9 μM) with high selectivity and rapid response towards free BR. The efficiency of energy transfer between GQD and BR was determined as 43%. Fluorescence spectra show a broad emission spectrum with a maximum fluorescence intensity at around 420 nm (λ_max) when excited at a wavelength of 320 nm. This 100 nm wavelength stokes shift is advantaged for employing GQDs for sensing applications.

1,3-Cyclohexadienes are an important group of molecules found in natural compounds and their metabolites. In this contribution, optimization, spectral prediction, reactivity, and molecular docking studies of 3-aminocyclohexa-2,6-diene-1-sulfonic acid were performed. The structure was optimized based on the crystallographic structures of cis-(1S)-3-Fluoro-3,5-cyclohexadiene-1,2-diol and 1,1′-(3,5-Cyclohexadiene-1,3-diyl)dibenzene. The most intense transitions in the predicted spectrum were observed at 195, 222, 235, and 324 nm. The molecular orbitals included in these transitions were partially localized on polar groups. The explicit solvent effect was investigated through optimization of structure with one water molecule. The strength of these interactions was assessed by the Natural Bond Orbital Theory and Quantum Theory of Atoms in Molecules. Three different dimer structures were also optimized to obtain the interaction energy for various active positions. The most stable dimer was formed through the interaction of amino and sulfonic groups. The reactivity parameters for three cyclohexadiene were calculated and discussed from the structural point of view. The docking study towards Urokinase Type Plasminogen Activator (uPa) proved the importance of various substituents. Once the dimers were used as ligands, the binding energy increased. These results show the possible use of cyclohexadienes as uPa inhibitors.

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The optimization of 3-aminocyclohexa-2,6-diene-1-sulfonic acid (1), cis-(1S)-3-Fluoro-3,5-cyclohexadiene-1,2-diol (2) and 1,1′-(3,5-Cyclohexadiene-1,3-diyl)dibenzene (3) compounds was performed at the B3LYP/6-311++G(2df,2p) level of theory. Strong hydrogen bonds were formed with amino and sulfonic groups. The dimer structures proved the importance of intermolecular interactions between polar groups. The docking results towards Urokinase Type Plasminogen Activator (uPa) proved the reactivity order determined previously along with the interactions with the amino acids in an active pocket.

The addition of bromoform to carbon-carbon and carbon-heteroatom multiple bonds has gathered interest from the synthetic community as it leads to brominated molecules that find applications in agrochemicals, pharmaceuticals, polymers, and radiolabeled agents. The chemistry of di- and tri-brominated functionalized olefins remains scarcely explored. It may be due to their high steric demand and their propensity to form halogen bonds. The addition of bromoform to olefins in the presence of protic bases and a phase-transfer catalyst is well-established. However, their metal-mediated versions leading to new brominated compounds did not receive much attention. The addition of bromoform mediated by metals provides an opportunity to construct various synthetic intermediates and understand the underlying mechanistic aspects. Herein, we present the approaches reported in the last two decades on the bromocyclopropanation, atom transfer radical additions, hydroalkylations, and conjugate additions of bromoform to electron-rich and electron-deficient olefins under metal-mediated conditions. These approaches are expected to set the stage for hitherto unexplored asymmetric transformations and synthesis of complex molecules, including natural products, involving metal-mediated bromoform addition as the key step.

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Reactions of bromoform with various multiple bonds such as olefins, carbonyl compounds, and imines under metal-mediated conditions are reviewed here. The methodology includes tribromomethylation, dibromomethylenation, dibromocyclopropanation, etc., and is a superior alternative to conventional base-mediated conditions.