Search Results (67)

The organic compounds 2-aminopyrimidine (AP) and 4-aminobenzoic acid (PABA) were selected for the synthesis of a compound by establishing the phase diagram and adopting the solid-state synthesis method. The phase diagram analysis suggested the formation of a novel intermolecular compound (IMC) at a 1:1 stoichiometric ratio of AP and PABA, along with two eutectics at 0.25 and 0.90 mole fractions of AP. FTIR and NMR spectroscopy were used for the structure elucidation of the intermolecular compound. The powder X-ray diffraction analysis revealed the novel nature of IMC (APPABA) and the mechanical mixture nature of eutectics. The sharp and single peak of the DSC curve suggested the melting and pure nature of the synthesized IMC. Various thermodynamic parameters of IMC and eutectics were studied. A single crystal of the IMC was grown from solution and its single-crystal X-ray diffraction analysis revealed that it crystallized in a monoclinic system with the P21/n space group. Hirshfeld surface analysis further validated the weak non-covalent interactions summarized through the single-crystal X-ray analysis. Studies on the IMC were thoroughly conducted to evaluate its antibacterial activity with reference to antibiotics, and it showed significant positive responses against various pathogenic microbial isolates (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella aerogenes, and Shigella boydii) and non-pathogenic microbial isolates (Enterobacter cloacae, Pseudomonas azotoformans, and Burkholderia paludis). It was also found effective against methicillin-resistant bacterial strains viz. Staphylococcus aureus MRSA. Full article

This work studies the effect of mesostructured silica–zirconia–tungstophosphoric acid (SiO₂-ZrO₂-TPA) composites used as catalysts in the synthesis of nifedipine by the Hantzsch methodology. The selectivity for nifedipine is determined, along with that of secondary products that may form depending on the reaction conditions. The materials were synthesized via the sol–gel method and characterized by N₂ adsorption–desorption isotherms, infrared spectroscopy (FT-IR), ³¹P solid-state nuclear magnetic resonance (NMR-MAS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectra (XPS), and potentiometric titration. The characterization results from the XPS spectra showed that as the Si/Zr ratio drops, the Si-O-Si signal size decreases, while the Zr-O signal size increases. Characterization by titration indicated that an increase in the total acidity of the material, resulting from support modification with tungstophosphoric acid (H₃PW₁₂O₄₀, TPA), enhances the reaction yield. The catalytic activity in the solvent-free Hantzsch reaction was evaluated under thermal heating and microwave irradiation. The experiments conducted at 80 °C achieved a maximum yield of 57% after 4 h of reaction using the Si20Zr80TPA30 catalyst (50 mg), while by microwave heating, the yield significantly improved, reaching 77% in only 1 h of reaction. This catalyst exhibited stability and reusability without significant loss of activity up to the third cycle. Depending on the type of material and the reaction conditions, it is possible to modify the selectivity of the reaction, obtaining a 1,2-dihydropyridine isomeric to nifedipine. Reaction intermediates and other minor secondary products that may be formed in the process were also evaluated. Full article

The synthesis of [Cu(PteN^˄N)(P^˄P)][BF₄] complexes with pterin-fused phenanthroline (PteN^˄N) derivatives and bisphosphine (P^˄P) co-ligands was achieved through a mechanochemical approach. Due to the extremely poor solubility of PteN^˄N ligands, traditional solution methods are ineffective, whereas solid-state mechanochemistry reliably yielded the targeted heteroleptic—rather than homoleptic—complexes with considerable stability even in solution. The transformation from ligand to complex increased the solubility dramatically. The ligands and complexes were comprehensively characterised with a mixture of routine spectroscopic and spectrometric methods, the applicability of which depended to some extent on the compounds’ solubility, e.g., in the case of NMR spectroscopy. The photophysical properties of the complexes, which were not as exciting as anticipated, were assessed by absorption and emission spectroscopic methods, showing that further improvements are needed in complex design if these species are to be developed towards photocatalysis in the future. Full article

The present study reports the ability of a fungal isolate Aspergillus ochraceus DY1, obtained from rotten wood, to degrade alkali lignin (AL) and lignocelluloses in an efficient manner. The efficiency of degradation was monitored by measuring the percentage of decolorization and utilizing GC-MS for identifying degradation products at different time intervals (10, 20, 30, and 40 days). The optimal degradation of alkali lignin (AL) was achieved at 0.01% concentration, 25 °C, and pH 7, resulting in 63.64% degradation after 40 days of incubation. A GC-MS analysis revealed significant degradation products, including n-hexadecanoic acid, octadecane, butylated hydroxytoluene, 2,6,11-trimethyl-dodecane, dibutyl phthalate, oleic acid, 3,5-dimethoxy-phenol acetate, and 2-(phenylmethylene)- cyclohexanone. Structural changes in AL were confirmed through HSQC 2D NMR and size-exclusion chromatography, indicating depolymerization and reduced molecular weight. Furthermore, A. ochraceus DY1 demonstrated substantial biomass loss in corn stover (62.5%) and sugarcane bagasse (50%) after 7 days of solid-state fermentation. Surface morphological depletion was observed in the bio-treated corn stover through SEM and confocal microscopy, which was not seen in the untreated one. These findings underscore the potential of A. ochraceus DY1 for efficient lignin degradation, with promising applications in biofuel production, waste management in the paper and pulp industry, and the synthesis of value-added bioproducts. Full article

Organometallic ruthenium complexes with p-cymene = 1-methyl-4-(1-methylethyl)-benzene and N^N = bidentate polypyridyl ligands constitute interesting candidates with biological and catalytic properties. Towards this aim, we have synthesized four ruthenium(II)–arene complexes of the type [Ru(η⁶-p-cymene)(N^N)Cl][X] (N^N = Br-Qpy = 6-bromo-4-phenyl-2-pyridin-2-yl-quinoline, X = Cl⁻ (1a); PF₆⁻ (1b); N^N = OH-Ph-Qpy = 4-(4-phenyl-2-(pyridin-2-yl)quinolin-6-yl)phenol, X = Cl⁻ (2a); PF₆⁻ (2b)). This is the first report of ruthenium(II) p-cymene complexes incorporating substituted pyridine–quinoline ligands, with –Br and –C₆H₄OH groups in the 6-position of quinoline. We also refer to the cytotoxicity of the ligands and their possible effect of modulating the activity of the ruthenium(II) complexes. These were characterized by a combination of spectroscopic methods (ATR-IR, UV–Vis, multinuclear NMR), elemental analysis, and conductivity measurements. The solid-state structure of 2b, determined by single-crystal X-ray diffraction, reveals a three-legged piano-stool geometry. The in vitro cytotoxic activities of the new complexes were evaluated in HEK293T (human embryonic kidney cells) and in HeLa cells (cervical cancer cells), via the MTT assay. Poor in vitro anticancer activities were observed for the HeLa cancer cell line, with 2a being the most potent (IC₅₀ = 75 μΜ). The cytotoxicity of Br-Qpy in HEK293T is comparable to that of cisplatin. Both complexes 1a and 1b successfully catalyze the transfer hydrogenation of benzophenone to benzhydrol by 2-propanol at 82 °C. The catalytic performance of 1a in the ratio of S:Cat:B = 400:1:40 (S = substrate, Cat = catalyst, B = base = KOiPr) leads to a conversion of 94%, within 3 h of reaction. Presumably, catalytic transformation takes place via ruthenium(II) hydride species being the active catalyst. Full article

Nitrilotris(methylenephenylphosphinic) acid (NTPAH₃) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe₃)₃. From the latter, upon alcoholysis in chloroform, NTPAH₃ could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH₃ synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H⋅⋅⋅O H-bonded networks (NTPAH₃^P), in chloroform crystals in the space group R3c formed (NTPAH₃^M), the constituents of which are individual molecules with exclusively intramolecular O-H⋅⋅⋅O hydrogen bonds. Both solids, NTPAH₃^P and NTPAH₃^M, were characterized by single-crystal X-ray diffraction, multi-nuclear (¹H, ¹³C, ³¹P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH₃^P and NTPAH₃^M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)₃ H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and ¹H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)₃ H-bond trimers of NTPAH₃^M over those in NTPAH₃^P. Full article

Organometallic complexes of the formula [Ru(N^N)(p-cymene)Cl][X] (N^N = bidentate polypyridyl ligands, p-cymene = 1-methyl-4-(1-methylethyl)-benzene, X = counter anion), are currently studied as possible candidates for the potential treatment of cancer. Searching for new organometallic compounds with good to moderate cytotoxic activities, a series of mononuclear water-soluble ruthenium(II)–arene complexes incorporating substituted pyridine–quinoline ligands, with pending -CH₂OH, -CO₂H and -CO₂Me groups in the 4-position of quinoline ring, were synthesized, for the first time, to study their possible effect to modulate the activity of the ruthenium p-cymene complexes. These include the [Ru(η⁶-p-cymene)(pqhyme)Cl][X] (X = Cl⁻ (1-Cl), PF₆⁻ (1-PF₆), pqhyme = 4-hydroxymethyl-2-(pyridin-2-yl)quinoline), [Ru(η⁶-p-cymene)(pqca)Cl][Cl] ((2-Cl), pqca = 4-carboxy-2-(pyridin-2-yl)quinoline), and [Ru(η⁶-p-cymene)(pqcame)Cl][X] (X = Cl⁻ (3-Cl), PF₆⁻ (3-PF₆), pqcame = 4-carboxymethyl-2-(pyridin-2-yl)quinoline) complexes, respectively. Identification of the complexes was based on multinuclear NMR and ATR-IR spectroscopic methods, elemental analysis, conductivity measurements, UV–Vis spectroscopic, and ESI-HRMS techniques. The solid-state structures of 1-PF₆ and 3-PF₆ have been elucidated by single-crystal X-ray diffraction revealing a three-legged piano stool geometry. This is the first time that the in vitro cytotoxic activities of these complexes are studied. These were conducted in HEK293T (human embryonic kidney cells) and HeLa cells (cervical cancer cells) via the MTT assay. The results show poor in vitro anticancer activities for the HeLa cancer cell lines and 3-Cl proved to be the most potent (IC₅₀ > 80 μΜ). In both cell lines, the cytotoxicity of the ligand precursor pqhyme is significantly higher than that of cisplatin. Full article

This study demonstrates the synthesis of five novel quaternary ammonium aldimines through a two-step synthetic route involving a condensation reaction between 4-pyridincarboxyaldehyde and 3,4,5-trimethoxyaniline, followed by the quaternization of the pyridine N-atom with various aromatic α-bromo ketones. The newly obtained compounds underwent characterization for both purity and molecular structure, utilizing HR-MS, 1D, and 2D NMR spectroscopy in solution, as well as a comparison between single-crystal and powder X-ray analyses in a solid state. The thermal behavior of the studied compounds was evaluated using differential scanning calorimetry (DSC). The antioxidant properties of the compounds were assessed through DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and ferric-reducing antioxidant power (FRAP) assays, employing Trolox as a standard. The performed in vitro antibacterial screening indicates a selective antibacterial activity against Gram-negative K. pneumoniae and P. aeruginosa, while no such activity is detected for Gram-negative E. coli and Gram-positive S. aureus. Full article

The reaction of the potassium salt of (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)-pyridine-2-yl]-amine (Ap*H) with the equimolar ratio of [ScCl₃] in tetrahydrofuran (thf) resulted in the mononuclear mono(aminopyridinato) scandium dichloride complex [Ap*ScCl₂(thf)₂]. An X-ray analysis showed the title compound to be monomeric. The compound [C₄₀H₅₉Cl₂N₂O₂Sc] crystallized in the monoclinic space group, P2₁/n, and possessed the following cell parameters: a  =  12.4441(8) b  =  22.9975(10) c  =  13.9971(8) Å, β  =  92.297(5)°, V  =  4002.5(4) A³, and Z  =  4. Hirshfeld analyses show that H…H (91.1%), H…C/C…H (5.0%), and H…Cl/Cl…H (3.9%) are the contributing interactions in the solid-state structure. The compound was further characterized by NMR spectroscopy, and its purity was confirmed by elemental analysis. Full article

The reaction of the dianionic species [Fe₂(CO)₆(μ-PPh)₂]²⁻ with ^tBuN(CH₂Cl)₂ gives the di-iron carbonyl aza-diphosphido-bridged complex [Fe₂(CO)₆(µ-{P(Ph)CH₂}₂N^tBu)] (1). Attempts to prepare 1 by click-chemistry by reacting [Fe₂(CO)₆(μ-PHPh)₂] with CH₂O and ^tBuNH₂ afforded a bis-phosphido compound [Fe₂(CO)₆(µ-P(Ph)CH₂NH^tBu)₂] (2) which exists as two, syn and anti, isolable isomers depending on the relative orientation of the groups carried by the phosphorus atoms. In the presence of HBF₄.Et₂O, in dichloromethane, 1 leads to the stabilized ammonium species [Fe₂(CO)₆(µ-{P(Ph)CH₂}₂NH^tBu)](BF₄) (3). The derivatives 1–3 were characterized by IR and ¹H, ³¹P-{¹H} NMR spectroscopies. Their structures in a solid state were determined by X-ray diffraction analyses, which accord with their spectroscopic characteristics. Full article

Catalytic dehydroaromatization of n-alkanes into high-value aromatics has garnered extensive interest from both academia and industry. Our group has previously reported that phosphorus-doped carbon materials exhibit high selectivity for C-H bond activation in the dehydroaromatization of n-hexane. In this study, using n-heptane as a probe, we synthesized biomass-based phosphorus-doped carbon catalysts to investigate the impact of hydrogen heat treatment and carbon deposition on catalyst structure. Despite achieving an initial conversion of n-heptane at approximately 99.6%, with a toluene selectivity of 87.9%, the catalyst activity fell quickly. Moreover, longer hydrogen treatment time and higher hydrogen concentrations were found to accelerate catalyst deactivation. Thermogravimetric analysis (TGA) and N₂ adsorption measurements (BET) indicated that a small amount of coke deposition was not the primary cause of catalyst deactivation. Temperature-programmed desorption of ammonia gas (NH₃-TPD) revealed a significant decrease in acid-active functional groups. X-ray photoelectron spectroscopy (XPS) and solid-state ³¹P NMR spectroscopy confirmed the reduction of active central phosphorus species. These results suggest that catalyst deactivation primarily arises from the decrease in acidity and the partial reduction of phosphorus-containing groups, leading to a substantial loss of active sites. This work contributes new perspectives to understanding the properties and design improvements of metal-free carbon catalysts. Full article

The tetrafluoroborate salt of the cationic Cu(I) complex [Cu(CHpz₃)(PPh₃)]⁺, where CHpz₃ is the tridentate N-donor ligand tris(pyrazol-1-yl)methane and PPh₃ is triphenylphosphine, was synthesized through a displacement reaction on the acetonitrile complex [Cu(NCCH₃)₄][BF₄]. The compound crystallizes in the monoclinic P2₁/c space group. The single-crystal X-ray diffraction revealed that the copper(I) centre is tetracoordinated, with a disposition of the donor atoms surrounding the metal centre quite far from the ideal tetrahedral geometry, as confirmed by continuous shape measures and by the τ₄ parameter. The intermolecular interactions at the solid state were investigated through the Hirshfeld surface analysis, which highlighted the presence of several non-classical hydrogen bonds involving the tetrafluoroborate anion. The electronic structure of the crystal was modelled using plane-wave DFT methods. The computed band gap is around 2.8 eV and separates a metal-centred valence band from a ligand-centred conduction band. NMR spectroscopy indicated the fluxional behaviour of the complex in CDCl₃ solution. The geometry of the compound in the presence of chloroform as implicit solvent was simulated by means of DFT calculations, together with possible mechanisms related to the fluxionality. The reversible dissociation of one of the pyrazole rings from the Cu(I) coordination sphere resulted in an accessible process. Full article

A fluorescent probe, N′-((3-methyl-5-oxo-1-phenyl-4, 5-dihydro-1H-pyrazol-4-yl) methylene)-2-oxo-2H-chromene-3-carbohydrazide (MPMC), was synthesized and characterized. Characterizations of the synthetic MPMC were conducted via proton nuclear magnetic resonance (¹HNMR) spectroscopy and carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR). The fluorescence emission behaviors of the MPMC probe towards diverse metal ions were detected, and the probe exhibited high sensitivity and selectivity towards Cu²⁺ over other metal ions via the quenching of its fluorescence. Furthermore, the existence of other metal actions made no apparent difference to the fluorescence intensity of the MPMC-Cu²⁺ system; that is, MPMC displayed a good anti-interference ability. Job’s plot of the MPMC and copper ions indicated that the detection limit was 10.23 nM (R² = 0.9612) for the assayed actions, with a stoichiometric ratio of 1:1 for MPMC and Cu²⁺. Additionally, the color of the MPMC probe solution changed from nearly colorless to yellow in the presence of Cu²⁺ in visible light, and the color change could be observed by the naked eye. Similarly, the color resolved from bright yellow into blue in ultraviolet light. Moreover, reusability studies indicated that the MPMC probe was reusable. The pH effect of the MPMC probe on Cu²⁺ had a broad range of pH detection, i.e., from 4.0 to 11.0. The response time of the MPMC probe for determining Cu²⁺ was within 1 min. The recognition of Cu²⁺ via MPMC performed on pre-treated paper under sunlight and UV light both had a distinct colour change. Thus, the solid-state method for detecting Cu²⁺ with the naked eye was both economical and convenient. Full article

Magnesium silicates combining acidic and basic surface properties are known to be interesting as heterogeneous catalysts. Nevertheless, their catalytic performances are highly dependent on the synthesis method used. In this study, a series of magnesium silicates was synthesized for the first time using a coprecipitation method with a micromixer. It is first shown that changes in synthesis/precipitation pH led to magnesium silicates with different Mg/Si ratios: the higher the synthesis pH, the higher the Mg/Si ratio. Moreover, prepared silicates with a final Mg/Si ratio greater than 0.7, thus prepared at high pH, exhibit negligible specific surface area, whereas relatively high values (>180 m²/g) have been obtained for lower Mg/Si ratios. A set of experimental characterization data obtained by N₂ physisorption, SEM, XRD, TGA-DTA as well as Raman and ²⁹Si NMR spectroscopies are presented and discussed. They show the existence of two distinct families with a similar Magnesium Silicate Hydrate (MSH) phase, but they reveal different aggregation states and textural properties. Finally, the surface acid–base reactivity of the co-precipitated magnesium silicates was determined using the model reaction of 2-methylbut-3-yn-2-ol (MBOH) conversion. The results obtained suggest that it is possible to prepare silicates with a wide range of surface acid–base properties, from purely basic solids to those with both acidic and basic properties, by adjusting the final Mg/Si ratio via the control of the synthesis parameters. Full article

A new copper(I) complex, [Cu₂(L)₂dppm](PF₆)₂ (1) [L = 3-(2-Pyridyl)-5,6-diphenyl-1,2,4-triazine and dppm: Bis(diphenylphosphino)methane], was prepared and characterized by IR, ¹H-NMR, ³¹P-NMR spectroscopy, elemental and thermogravimetric analysis, and a single-crystal X-ray diffraction technique. Complex 1 is a dinuclear compound, showing that L and dppm act as tridentate and bidentate chelating ligands, respectively. The two Cu(I) atoms exhibit a distorted tetrahedral coordination sphere embedded in N₃P environments. The supramolecular interactions in the solid-state structure are characterized by C−H···N, C−H···F, C-H···π and π···π intermolecular interactions, which we studied using Hirshfeld surface and fingerprint tools. Additionally, the complex was studied experimentally using UV–Vis spectroscopy and cyclic voltammetry, and theoretical studies with time-dependent density functional theory (TD-DFT) were performed. Moreover, the optical and electrochemical properties were studied, focusing on the band gap. Compound 1 was used as a co-sensitizer in a dye-sensitized solar cell, showing a good photovoltaic performance of 2.03% (Jsc = 5.095 mAcm⁻², Voc = 757 mV, and FF = 52.7%) under 100 mW cm⁻² (AM 1.5G) solar irradiation, which is similar to that of DSSC, which was only sensitized by N719 (2.2%) under the same condition. Full article