Spectroscopic Studies Research Articles

Novel AIE and solvatochromism exhibiting TPE based organic fluorophore with excellent emission properties in solid and solution phase for latent fingerprint and metronidazole sensing in real samples

Organic molecules with extended aromaticity are important when designing probes with optical properties. Herein, we designed and synthesized a novel tetraphenylethylene (TPE) based organic molecule TC exhibiting excellent photophysical characteristics. A thorough and in-depth study of the optical properties of probe TC was performed including solvatochromism, aggregation and solid-state studies using ultraviolet–visible (UV Vis) and fluorescence spectroscopy. Also, its optical properties under a UV 365 nm laser were investigated. The compound exhibited aggregation induced emission (AIE) which was thoroughly investigated in a H2O/DMF system and later utilized in formulation of invisible ink and latent fingerprint sensing. Moreover, the excellent emission properties of probe TC were utilized for the highly selective detection of the antibiotic metronidazole (MET) in real samples including human serum and artificial urine. Furthermore, portable TLC and paper-based strips were designed for the on-site detection of MET. Additionally, the mechanism of selective sensing of MET was thoroughly investigated through spectroscopic studies including titration NMR, fluorescence, UV Vis studies and DFT studies. Photoinduced electron transfer (PET) was attributed as the plausible sensing mechanism for the detection of MET. Scanning electron microscopy (SEM) also supported the sensing of MET through change in morphology. DFT calculations involved the measurement of thermodynamic stability, reduced density gradient (RDG) analysis, molecular orbital, and charge transfer studies as well as analysis of quantum theory of atoms in molecules (QTAIM). All the studies supported the presence of non-covalent interactions between probe TC and MET.

Expanding the scope of resonance Raman spectroscopy in hydrogenase research: New observable states and reporter vibrations

Oxygen-tolerant [NiFe] hydrogenases are valuable blueprints for the activation and evolution of molecular hydrogen under application-relevant conditions. Vibrational spectroscopic techniques play a key role in the investigation of these metalloenzymes. For instance, resonance Raman spectroscopy has been introduced as a site-selective approach for probing metal-ligand coordinates of the [NiFe] active site and FeS clusters. Despite its success, this approach is still challenged by a limited number of detectable active-site states – due to missing resonance enhancement or intrinsic light sensitivity – and difficulties in their assignment. Utilizing two oxygen-tolerant [NiFe] hydrogenases as model systems, we illustrate how these challenges can be met by extending excitation and detection wavelength regimes in resonance Raman spectroscopic studies. Specifically, we observe that this technique does not only probe low-frequency metal-ligand vibrations but also high-frequency intra-ligand modes of the diatomic CO/CN− ligands at the active site of [NiFe] hydrogenases. These reporter vibrations are routinely probed by infrared absorption spectroscopy, so that direct comparison of spectra from both techniques allows an unambiguous assignment of states detected by resonance Raman spectroscopy. Moreover, we find that a previously undetected state featuring a bridging hydroxo ligand between Ni and Fe can be probed using higher excitation wavelengths, as photoconversion occurring at lower wavelengths is avoided. In summary, this study expands the applicability of resonance Raman spectroscopy to hydrogenases and other complex metalloenzymes by introducing new strategies for probing and assigning redox-structural states of the active site.

Dielectric properties and impedance spectroscopic study of (1−x)[0.90NaNbO3–0.10Bi(Mg0.5Ta0.5)O3]–x(Bi0.5Na0.5)0.7(Sr0.7La0.2)0.3Ti0.9Zr0.1O3 ceramics

Dielectric properties and impedance spectroscopic study of (1−x)[0.90NaNbO3–0.10Bi(Mg0.5Ta0.5)O3]–x(Bi0.5Na0.5)0.7(Sr0.7La0.2)0.3Ti0.9Zr0.1O3 ceramics

Dynamics of magnetic inhomogeneity in La2CoMnO6 films probed by Raman spectroscopy

We report the dynamic effects of magnetic inhomogeneity on the temperature evolution of the Raman modes in polycrystalline La2CoMnO6 (LCMO) films. The LCMO films were obtained via chemical solution deposition and annealed at different temperatures, 700, 800 and 900 °C. Temperature-dependent Raman spectroscopic studies uncover anomalous phonon energy behaviors, associated with strong spin-phonon couplings revealed even at ambient conditions. This effect, which is observed to occur well above ferromagnetic ordering temperature is ascribed to short-range Mn4+/Co2+ ferromagnetic clusters. Moreover, our study has shown that spin-phonon coupling strength is governed by competing antiferromagnetic (AFM) and ferromagnetic (FM) interactions. These results significantly enhance the understanding of the complex spin-phonon coupling mechanism to provide insights into magnetic inhomogeneity in systems with two or more magnetic sublattices. These findings suggest the presence of similar effects in other double perovskites within the RE2CoMnO6 (RE = rare earths) family, which exhibit analogous magnetic sublattice and order–disorder defects.

Complementary Multisite Turnover Catalysis toward Superefficient Bifunctional Seawater Splitting at Ampere-Level Current Density.

The utilization of seawater for hydrogen production via water splitting is increasingly recognized as a promising avenue for the future. The key dilemma for seawater electrolysis is the incompatibility of superior hydrogen- and oxygen-evolving activities at ampere-scale current densities for both cathodic and anodic catalysts, thus leading to large electric power consumption of overall seawater splitting. Here, in situ construction of Fe4N/Co3N/MoO2 heterostructure arrays anchoring on metallic nickel nitride surface with multilevel collaborative catalytic interfaces and abundant multifunctional metal sites is reported, which serves as a robust bifunctional catalyst for alkaline freshwater/seawater splitting at ampere-level current density. Operando Raman and X-ray photoelectron spectroscopic studies combined with density functional theory calculations corroborate that Mo and Co/Fe sites situated on the Fe4N/Co3N/MoO2 multilevel interfaces optimize the reaction pathway and coordination environment to enhance water adsorption/dissociation, hydrogen adsorption, and oxygen-containing intermediate adsorption, thus cooperatively expediting hydrogen/oxygen evolution reactions in base. Inspiringly, this electrocatalyst can substantially ameliorate overall freshwater/seawater splitting at 1000mA cm-2 with low cell voltages of 1.65/1.69V, along with superb long-term stability at 500-1500mA cm-2 for over 200 h, outperforming nearly all the ever-reported non-noble electrocatalysts for freshwater/seawater electrolysis. This work offers a viable approach to design high-performance bifunctional catalysts for seawater splitting.

Operando spectroscopic studies on redox mechanism for CO2 hydrogenation to CO on In2O3 catalysts

The catalytic activities of In2O3 catalysts with different surface area for both cyclic unsteady-state (transient) and steady-state reverse water–gas shift (RWGS) reactions were systemically investigated. The initial CO formation rates during CO2-oxidation of the H2-reduced In2O3 catalysts were close to the CO formation rates in steady-state RWGS conditions at 325 °C, suggesting a redox mechanism for the steady-state RWGS reaction over the In2O3 catalysts. Transient kinetics for the In3+/In+ redox and products (H2O, CO) formation during the cyclic H2-reduction and CO2-oxidation of In2O3 under periodic feeding of H2 ↔ CO2 were studied by time-resolved operando UV–vis and In K-edge X-ray absorption experiments at 325 °C. During the H2-reduction, the surface In3+-O species was reduced to produce H2O and In+-□ (□: oxygen vacancy). Subsequent re-oxidation of the In+-□ by CO2 gave CO and the In3+-O species. The transient CO formation rates were close to the consumption rates of In+-□ under CO2, providing a quantitative evidence on the redox mechanism for unsteady-state RWGS reaction over In2O3. These results indicate that the unsteady-state and steady-state RWGS reactions are primary driven by the In3+/In+ redox mechanism. Kinetic results show that the reoxidation step is the rate-limiting step in the steady-state RWGS reaction.

From LaCrO3 towards LaCr0.2Mn0.2Fe0.2Al0.2Ga0.2O3 high-entropy ceramic compound: Crystal structure, dielectric and magnetic properties

A group of five perovskite-type ceramic systems was designed by solid-state reaction, increasing the configurational entropy, ΔSconf at the B-site, going from low and medium to finally reaching a high-entropy system. Chemical elements, crystal structure, and microstructure characterization, as well as the dielectric and magnetic properties, are discussed from the single phase LaCrO3 towards a continuous equiatomic multicomponent LaCr0.2Mn0.2Fe0.2Al0.2Ga0.2O3 ceramic compounds. Through a combination of structural analysis and XPS spectroscopy study, it is found that not only the configurational entropy ∆Sconf term, but also the enthalpy of mixing, ΔHmix through of arising of the coexistence of mixed valence state, oxygen vacancies, and local octahedral distortions lead to the stabilization of the single phase in equimolar multicomponent perovskite systems. The arising of Cr3+/Cr6+ and Mn3+/Mn2+ mixed valence state drives the AC electric conductivity through the presence of two kinds of charge carriers, small polarons and oxygen vacancies in LCM, LCMF, LCMFA, and LCMFAG ceramic compounds. The occurrence of these two classes of charge carriers progressively increases the AC electric conductivity at room and high temperatures for each ceramic compound, being higher for the LCMFA entropy compound, making it a potential candidate for solid oxide fuel cell (SOFC) applications. As expected, the increases of compositional random cations display rich magnetic properties arising from competing magnetic interactions driven by the sublattice of Cr, Mn, and Fe magnetic ions. The resulting ΔSconf increase leads to a Griffith-like phase. The results also show that not only the ferromagnetic clusters of the LaMnO3 (AxFz) sublattice but also the weak ferromagnetism associated with the LaCrO3 (GxFz), and LaFeO3 (GxFz) sublattices play a predominant role in the formation of the Griffiths-like phase in the low, medium and high-entropy ceramic systems.

Flexible magnesium-ion-conducting solid poly-blend electrolyte films for magnesium-ion batteries

Solid biodegradable polymer electrolyte systems are considered the optimal choice for energy storage devices because they are both cost-effective and energy-efficient. A solid blend polymer electrolyte (SBPE) membrane capable of transporting magnesium ions was prepared using a mixture of 70 wt% methylcellulose, 30 wt% chitosan, and varying wt% magnesium perchlorate salt. X-ray diffraction analysis revealed an increase in the amorphous nature caused by the inclusion of Mg(ClO4)2 salt in the polymer blend matrix. A Fourier transform infrared spectroscopy study of samples containing varying salt concentrations revealed secondary interactions between polymer segments and salt, which provides the basis for energy density. Moreover, through impedance analysis, it was determined that the bulk resistance decreased with increasing salt concentration. The SBPE containing 30 wt% magnesium perchlorate exhibited the highest ionic conductivity, with a value of 2.49 × 10–6 S cm−1. A comprehensive evaluation of the ion transport parameters, including mobility, carrier density, and diffusion, was conducted for the prepared electrolyte samples. Notably, an ionic transference number (tion) of approximately 0.83 was observed for the SBPE sample with 30 wt% magnesium salt, indicating ions’ prevalence as the system’s primary charge carriers. Electrochemical analyses demonstrated that the SBPE with the highest ion conductivity possessed an electrochemical stability window (ESW) of 1.92 V. Additionally, the thermal characteristics of the samples were evaluated using thermogravimetric analysis (TGA) to assess the thermal stability of the electrolyte. Finally, the highest conducting polymer electrolyte was employed to construct a primary magnesium battery, and its discharge profile with different cathode materials was studied. Based on these findings, the current study suggests an environmentally friendly, biodegradable, and economically viable electrolyte option suitable for separator cum electrolytes in magnesium-ion batteries.

A review of ion scattering spectroscopy studies at liquid interfaces with noble gas ion projectiles

Ion scattering spectroscopy (ISS) is an analytical tool that provides direct structural, topographical, and atomic compositional information at interfaces when noble-gas ions are used as projectiles. Since its development in 1967, ISS is commonly used to obtain quantitative information from solid interfaces. Over the last couple of decades, ISS has emerged as an important technique to probe liquid interfaces and their studies employing ISS has become not uncommon, more so with Neutral impact collision ion scattering spectroscopy (NICISS). Therefore, here the principle of ISS and its data evaluation are summarised while reviewing some important studies at vapor-liquid interfaces that provide direct information for molecular orientation of liquids (including ionic liquids), composition and distribution of atoms (or solutes) and charges as a function of depth to gain vast variety of thermodynamical information. Employing ISS such information can be achieved with high depth resolution of ~1–2 Å (depending on the nature of the experiment). These examples highlight the significance of ISS and show potential for its application for studies related to specific ion effects, atmospheric reaction in aerosol and sea water droplets, and even determining the fate of environmental pollutants like heavy metal ions and per-fluoroalkyl substances (PFAS). Furthermore, some limitations of ISS are also discussed relating to investigation of high-vapor pressure liquids and probing buried interfaces like liquid-liquid interfaces while presenting progresses made in probing solid-liquid interfaces.

Cost-effective Production of Titania Nanoparticles for the Modification of Transformer insulating oil

Nanofluids are prospective solutions for improving the transformer dielectric strengthby adding nanoparticles to the standard oils used in transformers.Oil-based titania nanofluids are becoming increasingly popular due to their superior insulating qualities and distinctive thermal performance, and they areconsideredas possible replacements in the domains of transformer insulating oils.This paper describes the industrial synthesis of titania nanoparticles for improving the insulating characteristics of virgin oil used in transformers.The titania nanoparticles were analyzed using an X-ray diffractogram (XRD), which revealed a prominent peak at Bragg angle 25O, indicating that the titania nanoparticles were generated in the anatase phase. Fourier transform infrared (FTIR) spectroscopy study endorsed the formation of Ti-O-Ti, Ti-OH, C-H and O-H stretching vibrations at 760 cm-1, 1345cm-1, 2475cm-1, and 3646 cm-1 wavenumbers respectively. Field emission scanning electron microscopy (FESEM) and Atomic Force Microscopy (AFM) examinations on the produced titania nanoparticles revealed that the particles had a circular shape with a diameter of 55nm and an average roughness value of roughly 3.6 nm respectively.The viscosity of the host virgin oil and the nanoparticles-filled nanofluid were examined, and higher viscosity values were found as particle concentration increased.The effective conductivity study with the zeta potential and thermal conductivity fluctuation with temperature variation also revealed that at higher temperatures, conductivity with the zeta potential increased and thermal conductivity dropped. Furthermore, the breakdown strength of the titania nanoparticles-based virgin oil was observed to be effectively increasedwith the particle concentration.

Synergetic benefits of zinc antimony oxide/reduced graphene oxide hybrid anode for enhanced sodium-ion storage

Organic-inorganic hybrid nanocomposites are rapidly evolving as a new generation of materials with attractive properties for electrochemical energy storage. Unfortunately, their practical applications in sodium-ion batteries (SIBs) still require further research due to the unsatisfactory cycling stability and rate performance. This work explores using zinc antimony oxide/reduced graphene oxide (ZSO/rGO) hybrid nanocomposite as an anode material in SIBs. After 150 cycles at 0.05 A g−1, the ZSO/rGO electrode delivers a specific capacity of 357.21 mAh g−1 with a coulombic efficiency of 99.3 %, which is almost 2.5-fold higher than the specific capacity of the pristine ZSO electrode. An in-situ Raman spectroscopy study demonstrates that the sodiation/desodiation mechanism in the ZSO/rGO electrode involves the conversion and alloying reactions in the ZSO nanoparticles. Further electrochemistry analysis reveals that the nanocomposite anode shows synergistic effects by coupling diffusion and surface contribution, in which the latter plays an important role.

Spectroscopic, anti-cancer, anti-bacterial and theoretical studies of new bivalent Schiff base complexes derived from 4-bromo-2,6-dichloroaniline

In this paper, four new mono-nuclear Ni(II), Pd(II), Pt(II) and Zn(II) complexes were prepared by using a bi-dentate Schiff base ligand, (E)-2-(((4-bromo-2,6-dichlorophenyl)imino)methyl)-5-chlorophenol (BrcOH), with bivalent ions in a methanol and distil water mixture as solvent in presence of NaOH as base. The structures of the prepared compounds were characterized by spectroscopic techniques (IR and 1H NMR), CHN analysis, and molar conductivity. The M(II) (Ni, Pd and Pt) ions are four-coordinated by a bi-dentate N2O2 donor ligand, forming square planar geometry, whereas the Zn(II) is coordinated as a tetrahedral geometry. The newly synthesized compounds, which include the Schiff base ligand and its complexes, underwent antibacterial screening against E. coli and S. aureus. The results demonstrated a remarkable and noteworthy biological activity of these compounds against these pathogenic bacterial strains. Different binding energies showed good correlation, with Pd showing the strongest binding. Small energy differences indicated high reactivity, with Ni and Pd complexes being the most reactive. Electrophilicity index exhibited electron-accepting properties, with Zn showing the highest reactivity. The dipole moments showed polarity and charge separation, with Pt having the highest polarity. We evaluated the pharmacokinetic properties (ADME) of a ligand and its metal complexes using the Swiss ADME website. The results of the in-silico prediction of physicochemical properties revealed that ten compounds in total adhered to Lipinski's rule.

Tracking the Photoactivity At The Interface of SiC/Poly 2(2-Thienyl) Furan Thin Solid Film in Polymer Gel Electrolytes

Assemblies made by immobilizing nanoparticles SiC into poly 2(2-thienyl) furane (PTF) were subjected to optical and electrochemical investigation. The studies show that SiC, a molecular inorganic compound, and PTF produce reproducible photo responses. Optical studies show that the optical band gap of SiC is around 2.5 eV while PTF's is around 2.2 eV. The band gap values suggest these assemblies absorb the visible solar radiation spectra. Electrochemical studies in gel electrolytes indicate that PTF and PTF/SiC under illumination show p-p behavior, where hole accumulation dominates. SiC thin films lack such character. Electrochemical Impedance Spectroscopy (EIS) studies revealed that the PTF and PTF/SiC possess kinetic and diffusional charge transfer properties. The studied assemblies and the gel electrolyte showed stability and resistance to photodegradation as evidenced by the regeneration of the same photo response after a longer period of experimentation.

Solution NMR backbone resonance assignment of the full-length resistance-related calcium-binding protein Sorcin.

Sorcin is a penta-EF hand calcium-binding protein that confers multidrug resistance in cancer cells. It regulates cellular Ca2+ homeostasis by interacting with calcium channels such as Ryanodine receptor 2 and Sarcoplasmic/endoplasmic reticulum Ca2+-ATPase in a calcium-dependent manner. The crystal structure of the Sorcin has been determined in both calcium-free and calcium-bound states to understand calcium-binding induced conformational change. However, due to its flexibility, most of the N-terminal domain is invisible in these crystal structures. Here we report the 1H, 13C, and 15N backbone resonance assignments of full-length Sorcin in the calcium-free state using solution NMR. The protein secondary structure was predicted based on the assigned backbone chemical shifts using TALOS+ and CSI 3.0. Our backbone resonance assignment of the full-length Sorcin provides a foundation for future NMR spectroscopic studies to uncover the mechanism of Ca2+ sensing by Sorcin.

Addressing the Challenge of a Simultaneous Destructive Assay of Plutonium and Uranium: Highly Precise, Robust, Universal, and Reagent-Free Differential Pulse Voltametric Method Development in Biodegradable Methanesulfonic Acid Medium.

The destructive assay of bulk uranium and plutonium, a cornerstone for chemical quality control and nuclear material accounting of fuel matrices, mandates robust and precise methodologies. Despite ongoing research, simultaneous, matrix independent determination of U and Pu has eluded solution owing to inherent limitations in aqueous acid medium, viz., coexistence of multiple oxidation states, coupled electrochemical reactions, smaller potential window, and requirement for multistep sample preconditioning and tedious electrode modification. The present study addresses this challenge wherein non-aqueous methanesulfonic acid (MSA) served the dual role of solvent and analyte media with a bare glassy carbon (GC) electrode. Fuel matrices, viz., (U, Pu)C, (U, Pu)O2, PuO2, UO3, UO2, and U3O8, were quantitatively dissolved in biodegradable MSA, without using any additives. Redox speciation of the analytes, U and Pu, in MSA was probed by ultraviolet-visible spectrophotometry and electrometry, revealing the absence of electrocatalytic regeneration and stabilization of single oxidation state, viz., U(VI) and Pu(IV), along with relevant redox-energetic (electron transfer and reversibility) and kinetic data. Bidentate coordination of MSA with the U analyte was indicated by X-ray absorption spectroscopy studies and was corroborated by density functional theory-based investigations, providing the optimized structure, viz., [UO2(MSA)2] and [Pu(MSA)4], binding modes and energy, partial charges, and molecular orbital diagrams. Based on these insights, the feasibility of differential pulse voltammetry (DPV)-based assay method development for U and Pu separately and in different U/Pu ratios, representing assorted fuel matrices, was probed. Analytical figures of merit for both U and Pu (detection limit of ∼10-5 M, precision of ∼0.2%, accuracy of ∼0.2%, high sensitivity, repeatability, and non-influence of relevant interferences) were determined, method validated employing actual fuel samples, and compared with the established, multi-step biamperometry method. Hence, a universal, simultaneous U and Pu destructive assay method in non-aqueous MSA media based on DPV with a commercial GC electrode was demonstrated.

The links among age, sex, and glutathione: A cross-sectional magnetic resonance spectroscopy study

Glutathione (GSH) is a brain marker for oxidative stress and has previously been associated with cerebral amyloid deposition and memory decline. However, to date, no study has examined the links among GSH, sex, age, amyloid, and Apolipoprotein E (APOE) genotype in a large non-clinical cohort of older adults. We performed APOE genotyping, magnetic resonance spectroscopy (MRS) as well as simultaneous positron emission tomography with the radiotracer Flutemetamol (Amyloid-PET), in a group of older adults. The final analysis set comprised 140 healthy older adults (mean age: 64.7 years) and 49 participants with mild cognitive impairment (mean age: 71.4 years). We recorded metabolites in the posterior cingulate cortex (PCC) by a GSH-edited MEGAPRESS sequence. Structural equation modeling revealed that higher GSH levels were associated with female sex, but neither APOE- epsilon 4 carrier status nor age showed significant associations with GSH. Conversely, older age and the presence of an APOE4 allele, but not sex, are linked to higher global amyloid load. Our results suggest that the PCC shows sex-specific GSH alterations in older adults.

Reorientation of interfacial water molecules during melting of brain sphingomyelin is associated with the phase transition of its C24:1 sphingomyelin lipids

Melting of brain sphingomyelin (bSM) manifests as a broad feature in the DSC curve that encompasses the temperature range of 25 – 45 °C, with two distinguished maxima originating from the phase transitions of two the most abundant components: C24:1 (Tm,1) and C18:0 (Tm,2). While C24:1/C18:0 sphingomyelin transforms from the gel/ripple phase to the fluid/fluid phase, the dynamics of water molecules in the interfacial layer remain completely unknown. Therefore, we carried out a calorimetric (DSC), spectroscopic (temperature-dependent UV-Vis and fluorescence) and MD simulation study of bSM in the absence/presence of Laurdan® (bSM ± L) suspended in Britton-Robinson buffer with three different pH values, 4 (BRB4), 7 (BRB7) and 9 (BRB9), and of comparable ionic strength (I = 100 mM). According to DSC, T̅m, 1 (≈ 34.5 °C/≈ 32.1 °C) and T̅m, 2 (≈ 38.0 °C/≈ 37.2 °C) of bSM suspended in BRB4, BRB7, and BRB9 in the absence/presence of Laurdan® are found to be practically pH-independent. Turbidity-based data (UV-Vis) detected both qualitative and quantitative differences in the response of bSM suspended in BRB4/BRB7/BRB9 (T̅m: ∼ 35 °C/32.0 ± 0.2 °C/36.4 ± 0.4), suggesting an intricate interplay of weakening of van der Waals forces between their hydrocarbon chains and of increased hydration in the polar headgroups region during melting. The temperature-dependent response of Laurdan® reported a discontinuous, pH-dependent change in the reorientation of interfacial water molecules that coincides with the melting of C24:1 lipids (on average, T̅m (LTC/HTC): ≈ 31.8 °C/30.6 °C/30.5 °C). MD simulations elucidated the impact of Laurdan® on a change in the physicochemical properties of bSM lipids and characterized the hydrogen bond network at the interface at 20 °C and 50 °C.

Spectroscopic and computational study of molecular interaction of Pexidartinib with homologous mammalian transport proteins

Binding of biologically important molecules with plasma proteins highly influence its availability, distribution, and metabolism, and thus has great significance in determining its therapeutic efficiency. Hence, studying its interaction with plasma proteins is prime and inevitable. Herein, we have investigated the molecular interaction of Pexidartinib, a novel, primitive and highly selective therapeutical agent against CSF-1R overexpression, with human serum albumin (HSA) and bovine serum albumin (BSA) using various spectroscopic methods, docking and simulations. The intrinsic fluorescence of the proteins considerably quenched on PEX addition accompanied by a slight blue shift. The complex formation between PEX and BSA/HSA induced some alterations in the molecular milieu of the tryptophan residues. The active binding locus was found to be within the hydrophobic cavity of Sudlow site I of both BSA and HSA. The binding dynamics suggest the interplay of hydrogen bonding and hydrophobic interactions in complex stabilisation. MD simulations provides valuable insights into the dynamic facets of the molecular recognition processes involved and governs the stability factor of protein post ligand complexation.

Access to diverse carbonyl compounds by catalyst-free and photoinduced aerobic cleavage of C=N bonds.

Functional group interconversion is of great significance in organic synthesis. However, aerobic cleavage of C=N bonds to access carbonyl compounds still suffered from some limitations such as harsh reaction conditions, stoichiometric oxidants, poor substrate scope and use of toxic reagents. Herein, we report a catalyst-free and photo-induced aerobic cleavage of C=N bonds to afford diverse carbonyl compounds using oxygen from air as green oxidant. This mild methodology permits N-tosylhydrazones converted into the corresponding carbonyl compounds including ketones, amides, aldehydes and carboxylic acids, showing broad functional group tolerance and compatibility. Moreover, the gram-scale reaction and post-modification of complicated molecules proved the applicability and efficiency of this strategy. Finally, a plausible mechanism was proposed based on spectroscopic investigations and detailed mechanistic studies.

Gold(III) complexes with chloride and cyanopyridines: Facilitated hydrolysis of nitrile ligand to amide and antibacterial activity

A range of novel simple gold(III) compounds has been synthesized in their monocrystalline form, including two previously unknown chloro-complexes of Au3+ with 2-cyanopyridine or 3-cyanopyridine, respectively. Our investigations have revealed the intricate nature of the reaction between 2-cyanopyridine and tetrachloroauric acid, yielding at least three distinct products. The main product, obtained in high yield, is a salt featuring a tetrachloroauric anion and a pyridinium cation stabilized by a hydrogen bond to a further 2-cyanopyridine molecule. Moreover, we observed the in-situ formation of a 2-cyanopyridine-AuCl3 complex, which undergoes hydrolysis of the nitrile bond to yield a picolinamide-Au(III) complex. The complexes were characterized by IR and Raman spectroscopies, NMR spectroscopy, and single-crystal XRD studies. Additional computational studies were conducted to explain unusual spectral features, the observed disparities in the complexation reactions of the three isomeric cyanopyridine ligands and the distinct reactivity of the complex with 2-cyanopyridine. Based on these studies, we propose a mechanism for the catalyzed hydrolysis of the nitrile bond within the Au(III) complex. Finally, we assessed the antimicrobial efficacy of the synthesized gold(III) complexes against a spectrum of bacteria and fungi.