Monatshefte Fur Chemie最新文献

This study describes the first application of an improved procedure on a pencil graphite electrode decorated with functionalized multi-walled carbon nanotubes (f-MWCNTs/PGE) for the determination of the COVID-19 antiviral drug, favipiravir (FVP). The electrochemical behavior of FVP at f-MWCNTs/PGE was examined by cyclic voltammetry and differential pulse voltammetry (DPV) methods, and it was noted that the voltammetric response significantly increased with the modification of f -MWCNTs to the surface. The linear range and limit of detection from DPV studies were determined as 1-1500 µM and 0.27 µM, respectively. In addition, the selectivity of the method was tested toward potential interferences, which can be present in pharmaceutical and biological samples, and it was found that f-MWCNTs/PGE showed high selectivity for the determination of FVP in the presence of probable interferences. The results with high accuracies and precisions from the obtained feasibility studies also revealed that the designed procedure can be used for accurate and selective voltammetric determination of FVP in real samples.

Graphical abstract:

Molecular docking simulation is a very popular and well-established computational approach and has been extensively used to understand molecular interactions between a natural organic molecule (ideally taken as a receptor) such as an enzyme, protein, DNA, RNA and a natural or synthetic organic/inorganic molecule (considered as a ligand). But the implementation of docking ideas to synthetic organic, inorganic, or hybrid systems is very limited with respect to their use as a receptor despite their huge popularity in different experimental systems. In this context, molecular docking can be an efficient computational tool for understanding the role of intermolecular interactions in hybrid systems that can help in designing materials on mesoscale for different applications. The current review focuses on the implementation of the docking method in organic, inorganic, and hybrid systems along with examples from different case studies. We describe different resources, including databases and tools required in the docking study and applications. The concept of docking techniques, types of docking models, and the role of different intermolecular interactions involved in the docking process to understand the binding mechanisms are explained. Finally, the challenges and limitations of dockings are also discussed in this review.

Graphical abstract:

The acid-base equilibria of six ACE inhibitors (ACEIs), captopril, cilazapril, enalapril, lisinopril, quinapril, and ramipril, were investigated in the presence of micelles of nonionic surfactant Brij 35. The pK_a values were potentiometrically determined at 25 °C and at a constant ionic strength (0.1 M NaCl). The obtained potentiometric data were evaluated in the computer program Hyperquad. On the basis of the shift in the pK_a values (ΔpK_a) determined in micellar media in relation to the pK_a values previously determined in "pure" water, the effect of Brij 35 micelles on ACEIs ionization was estimated. The presence of nonionic Brij 35 micelles caused a shift in the pK_a values of all ionizable groups of the investigated ACEIs (ΔpK_a from - 3.44 to + 1.9) while shifting the protolytic equilibria of both acidic and basic groups toward the molecular form. The Brij 35 micelles expressed the most pronounced effect on the ionization of captopril among the investigated ACEIs and stronger effect on the ionization of amino than on the ionization of carboxyl groups. The obtained results suggest that ionizable functional groups of ACEIs are involved in interactions with palisade layer of nonionic Brij 35 micelles, which potentially can be considered in physiological conditions. Distribution diagrams of the investigated ACEIs equilibrium forms as a function of pH indicate that the change in distribution is most strongly expressed in pH range 4-8, which includes biopharmaceutically important pH values.

Graphical abstract:

The synthesis, characterization, and reactivity of several new Cr(II) and Cr(III) complexes featuring an NCN pincer ligand with an arene backbone connected to amine donors NEt₂ and NiPr₂ via CH₂-linkers is described. Reacting the in situ lithiated ligand precursor N(C-Br)N^CH2-Et with [CrCl₃(THF)₃] resulted in the formation of the Cr(III) complex trans-[Cr(κ³NCN-NCN^CH2-Et)(Cl)₂(THF)]. Upon reaction of lithiated N(C-Br)N^CH2-iPr with a suspension of anhydrous CrCl₂, the Cr(II) complex [Cr(κ²NC-NCN^CH2-iPr)₂] is formed featuring two NCN ligands bound in κ²NC-fashion. In contrast, when lithiated N(C-Br)N^CH2-iPr is reacted with a homogeneous solution of anhydrous CrX₂ (X = Cl, Br), complexes [Cr(κ³NCN-NCN^CH2-iPr)X] are obtained. Treatment of [Cr(κ³NCN-NCN^CH2-iPr)Cl] with 1 equiv of PhCH₂MgCl and LiCH₂SiMe₃ afforded the alkyl complexes [Cr(κ³NCN-NCN^CH2-iPr)(CH₂Ph)] and [Cr(κ³NCN-NCN^CH2-iPr)(CH₂SiMe₃)]. All Cr(II) complexes exhibit effective magnetic moments in the range of 4.7-4.9 µ_B which is indicative for d⁴ high spin systems. If a solution of lithiated N(C-Br)N^CH2-iPr is treated with CrCl₂, followed by addition of an excess of Na[HB(Et)₃], the dimeric complex [Cr(κ²NC-NCN^CH2-iPr)(μ₂-H)]₂ is obtained bearing two bridging hydride ligands. [Cr(κ³NCN-NCN^CH2-iPr)(CH₂SiMe₃)] turned out to be catalytically active for the hydrosilylation of ketones at room temperature with a catalyst loading of 1 mol%. X-ray structures of all complexes are presented.

Graphical abstract:

Supplementary information: The online version contains supplementary material available at 10.1007/s00706-023-03128-6.

The spatial organization of metal oxide nanoparticles represents an important factor in the chemical utilization of resulting structures. For the production of networks that are composed of metal oxide nanoparticle chains, we dispersed vapor phase-grown TiO₂ and ZnO nanoparticles homogeneously in an aqueous polyvinyl alcohol solution. After electrospinning, we analyzed the sizes and diameters of the compositionally homogeneous electrospun fibers and discussed the size distribution and morphology of the nanoparticles inside. Calcination-induced polymer removal gives rise to self-supported nanoparticle-based nanofibers. Particle coarsening by a factor of ~ 2 for TiO₂ and ~ 3 for ZnO nanoparticles is observed.

Graphical abstract:

Herein, we present a new route to synthesize poly(2-oxazoline)s (POx) with coumarin moieties as pendant groups that can be crosslinked by irradiation to form hydrogels. The synthesis of a novel coumarin-containing 2-oxazoline monomer, 2-[(4-methyl-7-coumarinyloxy)methyl]oxazoline is described in four steps and further its subsequent homo- and copolymerization with 2-ethyl-2-oxazoline (EtOx) via cationic ring-opening polymerization (CROP). The received polymers with different coumarin content (8, 4 and 2 mol%) were compared with a known copolymer synthesized via postpolymerization modification of partially hydrolyzed poly(2-ethyl-2-oxazoline) (PEtOx) with a coumarin derivative. The thermoresponsive behavior of the POx in aqueous solutions was investigated, showing a clear difference in the cloud point temperature (T _cp ) between the polymers synthesized via different strategies. The hydrogel formation was achieved by irradiation with UV light by the following two methods: on the one hand with the pure coumarin-containing POx and on the other hand mixed with poly(ethylene glycol) diacrylate (PEGDA). The obtained hydrogels were compared regarding their swelling degree and their gel content, whereas the swelling degree in water of prepared hydrogels can be tuned by using POx by varying the coumarin content.

Graphical abstract:

Supplementary information: The online version contains supplementary material available at 10.1007/s00706-022-03013-8.

Treatment of [Co₂(CO)₈] with the ipso-substituted P(C-X)P^Y ligands (X = Br, Cl; R = iPr, tBu) bearing Y = NH and CH₂ linkers under solvothermal conditions affords the five-coordinate Co(I) and Co(III) complexes [Co^I(PCP^Y-R)(CO)₂] and [Co^III(PCP^Y-R)X₂]. The later are paramagnetic exhibiting a solution magnetic moment in the range of 3.0-3.3 μ_B which is consistent with a d⁶ intermediate spin system corresponding to two unpaired electrons. In the case of P(C-X)P^Y ligands (X = Br, Cl; R = tBu; Y = NH) the formation of the square planar Co(II) complex [Co(PCP^NH-tBu)X] was favored. This complex gives rise to a magnetic moment of 1.8 μ_B being consistent with a d⁷ low spin system corresponding to one unpaired electron. All complexes are characterized by means of spectroscopic techniques (NMR, IR), HR-MS. Representative complexes were also characterized by X-ray crystallography.

Graphical abstract:

Supplementary information: The online version contains supplementary material available at 10.1007/s00706-023-03123-x.

Binding of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol (C1), a biologically active substance, to bovine blood plasma albumin (BSA) at 293, 298, and 303 K was studied using fluorescence (steady state, synchronous, excitation/emission matrix) and FT-IR spectroscopy methods. The experimental results showed that C1 causes fluorescence quenching of BSA through both static and dynamic quenching mechanisms. The thermodynamic parameters, enthalpy and entropy change, for the static quenching were calculated to be - 35.73 kJ mol^-1 and - 35.34 J mol^-1 K^-1, which indicated that hydrogen bonding and van der Waals interactions were the predominant intermolecular forces regulating C1-BSA interactions. Distance between donor and acceptor (2.14, 2.26, and 2.30 nm) depending on the temperature, obtained from intrinsic Förster resonance energy transfer calculations, revealed the static quenching mechanism of BSA fluorescence in 0-3.0 × 10^-5 mol/dm³ concentration range of C1. The micro-environmental and conformational changes in BSA structure, established by synchronous, excitation/emission matrices and FT-IR spectra showed the changes in the BSA secondary structure.

Graphical abstract: