Spectroscopic Methods Research Articles

Synthesis of Iron(IV) Alkynylide Complexes and Their Reactivity to Form 1,3‐diynes

The isolation of thermally unstable and highly reactive organoiron(IV) complexes is a challenge for synthetic chemists. In particular, the number of examples where the C‐based ligand is not part of the chelating ligand remains scarce. These compounds are of interest because they could pave the way to designing catalytic cycles of bond forming reactions proceeding via organoiron(IV) intermediates. Herein, we report the synthesis and characterization, including single‐crystal X‐ray diffraction, of a family of alkynylferrates(III) and Fe(IV) alkynylide complexes. The alkynylferrates(III) are formed by transmetalation of the Fe(III) precursor [(N3N’)FeIII] (N3N’ is tris(N‐tert‐butyldimethylsilyl‐2‐amidoethyl)amine)) with lithium alkynylides, and their further one‐electron oxidation enables the synthesis of the corresponding Fe(IV) alkynylides. The electronic structure of this family of organometallic Fe(III) and Fe(IV) complexes has been thoroughly investigated by spectroscopic methods (EPR, NMR, 57Fe Mössbauer, X‐Ray absorption (XAS) and emission (XES) spectroscopies) and theoretical calculations. While alkynylferrates(III) are sluggish to engage into C–C bond forming processes, the Fe(IV) alkynylides react to afford 1,3‐diynes at room temperature. A bimolecular reductive elimination from a bimetallic iron(IV) intermediate to form the 1,3‐diynes is proposed based on the mechanistic investigations performed.

Synthesis of Iron(IV) Alkynylide Complexes and Their Reactivity to Form 1,3‐diynes

The isolation of thermally unstable and highly reactive organoiron(IV) complexes is a challenge for synthetic chemists. In particular, the number of examples where the C‐based ligand is not part of the chelating ligand remains scarce. These compounds are of interest because they could pave the way to designing catalytic cycles of bond forming reactions proceeding via organoiron(IV) intermediates. Herein, we report the synthesis and characterization, including single‐crystal X‐ray diffraction, of a family of alkynylferrates(III) and Fe(IV) alkynylide complexes. The alkynylferrates(III) are formed by transmetalation of the Fe(III) precursor [(N3N’)FeIII] (N3N’ is tris(N‐tert‐butyldimethylsilyl‐2‐amidoethyl)amine)) with lithium alkynylides, and their further one‐electron oxidation enables the synthesis of the corresponding Fe(IV) alkynylides. The electronic structure of this family of organometallic Fe(III) and Fe(IV) complexes has been thoroughly investigated by spectroscopic methods (EPR, NMR, 57Fe Mössbauer, X‐Ray absorption (XAS) and emission (XES) spectroscopies) and theoretical calculations. While alkynylferrates(III) are sluggish to engage into C–C bond forming processes, the Fe(IV) alkynylides react to afford 1,3‐diynes at room temperature. A bimolecular reductive elimination from a bimetallic iron(IV) intermediate to form the 1,3‐diynes is proposed based on the mechanistic investigations performed.

Bioassay‐Guided Extraction and Isolation of Natural Herbicides from Dried Zanthoxylum limonella Alston Fruits

AbstractWeeds are problematic plant species around the world. Various strategies exist for controlling weeds, but chemical treatment remains the preferred method, particularly when using natural substances. In this research, a crude aqueous‐methanol extract from dried Zanthoxylum limonella fruits was acid‐base partitioned into four fractions: neutral extract (NE), acid extract (AE), basic extract (BE), and aqueous extract (AQ). These fractions were further separated into seventeen subfractions: NEF1 to NEF7, AEF1 to AEF5, and BEF1 to BEF5, which were then tested for herbicidal activity against the growth of Chinese amaranth (Amaranthus tricolor) and barnyard grass (Echinochloa crus‐galli). Active subfractions were isolated via column chromatography and identified using spectroscopic methods, yielding seven active compounds: xanthoxyline (1), tambulin (2), atanine (3), prudomestin (4), skimmianine (5), p‐methoxybenzoic acid (6), and methyl caffeate (7). Compounds 2–7 had not been previously reported in Z. limonella. Xanthoxyline (1) was identified as the most potent botanical herbicide, fully inhibiting seed germination of Chinese amaranth and barnyard grass. This compound also decreased seed imbibition and α‐amylase activity in both species. Molecular docking studies on the α‐amylase enzyme (PDB ID: 1BG9) revealed that the aromatic, hydroxy, and carbonyl groups of xanthoxyline (1) interact with the enzyme's active sites.

PnictogenIII Dications Supported by BZIMPY Ligands.

Two homologous series of pnictogen(III) dications, stabilized by 2,6-bis(benzimidazole-2-yl)pyridine ligands have been prepared. Both series contain PnIII-X moieties (Pn = P, As, Sb, Bi; X = Cl or Ph) and have been fully characterized using spectroscopic methods including X-ray crystallography. The Lewis acidity of these compounds has also been probed by computational methods; the results suggest that the dictations are strong Lewis acids, with the PnCl2+ compounds being more acidic than the PnPh2+ compounds, and with Lewis acidity increasing from P to Bi, in both series. The PhP2+-containing compound was also found to be a versatile PIII transfer reagent, leading to new synthetic routes for various PhP-containing compounds. The redox chemistry of all compounds has also been probed using cyclic voltammetry and chemical reductions. In some cases the resulting PnI moieties could be trapped using diazabutadienes.

Recent advancements in meat traceability, authenticity verification, and voluntary certification systems

The growing demand for transparency in the food industry has led to significant advancements in meat traceability. Ensuring the authenticity and origin of meat products is critical for consumer trust, public health, and compliance with regulations. This paper reviews recent innovations in meat traceability, with a focus on blockchain technology as a novel approach to ensuring traceability. Additionally, advanced methods for verifying meat authenticity and origin, such as isotope fingerprinting, DNA analysis, and spectroscopic methods, are discussed. The role of voluntary certification schemes in enhancing traceability and authenticity verification in the meat industry is also explored. The findings highlight the importance of integrating cutting-edge technologies and certification schemes to build a robust and transparent meat supply chain.

Two New Alkaloids of the Endophytic Fungus Rhizopus oryzae From Atractylodes macrocephala Koidz.

Two new alkaloids, named migenomycin I (1) and II (2), along with nine known compounds (3-11), were isolated from the fungus Rhizopus oryzae from Atractylodes macrocephala Koidz. The structures of compounds 1 and 2 were determined by spectroscopic methods (MS, NMR, and CD). All compounds were isolated from Rhizopus oryzae for the first time. In addition, the antitumor activities of compounds 1 and 2 and the hypoglycemic activities of most compounds were evaluated.

Design, Synthesis, ssDNA Binding Affinities, and Evaluation of Novel Metal‐Centered Ferrocene as an Effective Antimicrobial and DNA Cleavage Agent

ABSTRACTMetal (Co3+, Ni2+, and Pt2+)–centered and noncentered ferrocene–Schiff bases were prepared. They have been structurally characterized by spectroscopic methods, elemental analysis, conductivity, and magnetic moment. Electron spin resonance was used for the characterization of the Co3+‐centered complex. All synthesized compounds showed antibacterial activity against all tested Gram‐positive and Gram‐negative strains, as well as potent antifungal effect against Candida species. Remarkably, these compounds demonstrated greater efficacy against Gram‐positive bacteria than Gram‐negative. Without an additional oxidant or reductant, the compounds exhibited DNA cleavage capability in the dark. The development of synthesized novel chemical compounds having DNA cleavage and antimicrobial activity plays a profound role in the advancement of medical therapeutics.

Characterization of glomalin proteins in soil: A potential indicator of erosion intensity

Abstract In this study, in a pioneering effort, glomalin proteins were extracted and geochemically characterized from soil in Serbia. Standard chemical (dry combustion, Walkley-Black) and spectroscopic methods (fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), scanning electron microscope (SEM)) were used to gain insight into the glomalin proteins. Samples from the City of Novi Sad (Serbia) were used for characterization and comparison. The soil contained an average of 17 mg/g of glomalin, representing ≈21% of the soil organic matter. DLS zeta potential analysis and the FTIR spectra reveal two significant differences before and after glomalin extraction, indicating a relationship between sand fractions and organic matter that affects particle aggregation and erosion potential. A comparison of SEM images and DLS results reveals that the glomalin extract consists of two particle size groups (0.08–1 and 6 µm), suggesting that the extraction process isolates only a smaller fraction of proteins and less tightly bound particles, indicating that soil aggregation is influenced by both mineralogy and the characteristics of organic matter. Hence, our research raises important questions about the role of glomalin in mitigating soil degradation processes, particularly soil erosion. Our study will enhance the overall understanding of glomalin, inspire future research, and prove beneficial for the sustainable restoration of degraded lands.

Illuminating Malaria: Spectroscopy’s Vital Role in Diagnosis and Research

Spectroscopic techniques have emerged as crucial tools in the field of malaria research, offering immense potential for improved diagnosis and enhanced understanding of the disease. This review article pays tribute to the pioneering contributions of Professor Henry Mantsch in the realm of clinical biospectroscopy, by comprehensively exploring the diverse applications of spectroscopic methods in malaria research. From the identification of reliable biomarkers to the development of innovative diagnostic approaches, spectroscopic techniques spanning the ultraviolet to far-infrared regions have played a pivotal role in advancing our knowledge of malaria. This review will highlight the multifaceted ways in which spectroscopy has contributed to the field, with a particular emphasis on its impact on diagnostic advancements and drug research. By leveraging the minimally invasive and highly accurate nature of spectroscopic techniques, researchers have made significant strides in improving the detection and monitoring of malaria parasites. These advancements hold the promise of enhancing patient outcomes and aiding in the global efforts towards the eradication of this devastating disease.

The bioactive constituents from the fruits of Elaeagnus angustifolia L.

Multiple spectroscopic, chromatographic, and chemical reaction methods were combined to investigate the chemical components in the fruits of Elaeagnus angustifolia L. As results, thirty-two compounds were obtained from it as natural products. Six of them, elangphenosides A (1), B (2), C (3) and D (4), elangmegastigmanoside A (5), and elangorganic acid A1 (6) were retrieved by Scifinder as previously undescribed ones. Additionally, a previously undescribed artificial product, elangorganic acid A2, as well as a known artificial one, (3R) 5-ethoxy-3-(ethoxycarbonyl)-3-hydroxy-5-oxopentanoic acid, were yielded. Following the phytochemical investigation, LC-MS analysis was employed to conduct a systematical characterization of the constituents from E. angustifolia fruits. Ultimately, fifty-six compounds, including seventeen phenols, one ionone, twenty-four triterpenes, and fourteen other ones, were unambiguously detected and identified. Moreover, in vitro anti-inflammatory activity screening of forty-four natural compounds presented in E. angustifolia fruits was performed by using the LPS-induced RAW264.7 cell model. Twenty-six compounds, including phenols, organic acids, and other compounds, showed assignable activity. Furthermore, their structure-activity relationships were summarized. Combined with the previous research work in our lab, triterpenes, phenols, and organic acids were speculated to be key components during the E. angustifolia fruits exerting anti-inflammatory activity. In summary, this article fully explored the chemical composition of E. angustifolia fruits, assayed their in vitro NO production inhibitory effects, greatly expanding its material foundation and laying a solid foundation for further research and development.

Substitution of the axial Type 1 Cu Ligand Afford Binding of a Water Molecule in Axial Position Affecting Kinetics, Spectral, and Structural Properties of the Small Laccase Ssl1.

Multicopper oxidases use Cu ions as cofactors to oxidize various substrates. High reduction potential at Type 1 Cu is considered as crucial for effective catalysis. Previous studies have shown that replacing the axial methionine ligand of the Type 1 Cu with leucine or phenylalanine leads to an increased reduction potential, but not always to higher enzyme activity. Here we present a study of six variants of the small laccase Ssl1 from Streptomyces sviceus, where the axial methionine ligand was substituted and the effect of the axial ligand on reduction potential, activity, spectral properties and structure was investigated. Absorption, electronic circular dichroism and EPR spectra revealed the presence of a stronger coordinating axial ligand like oxygen, which influences the electronic and catalytic properties more than the nature of the amino acid side chain. The crystal structures of the Ssl1 variants were solved, which show that none of the amino acids side chains coordinates to the Cu. Instead, a water molecule is found in the axial coordination site, which support the spectroscopic data. Our findings highlight the importance of combining structural and spectroscopic methods to investigate the effect of amino acid exchange on multicopper oxidases.

Tribute to Kenneth Sauer (1931-2022): a mentor, a role-model, and an inspiration to all in the field of photosynthesis.

Kenneth (Ken) Sauer was a mainstay of research in photosynthesis at the University of California, Berkeley and the Lawrence Berkeley National Laboratory (LBNL) for more than 50years. Ken will be remembered by his colleagues, and other workers in the field of photosynthesis as well, for his pioneering work that introduced the physical techniques whose application have enriched our understanding of the basic reactions of oxygenic photosynthesis. His laboratory was a training ground for many students and postdocs who went on to success in the field of photosynthesis and many others. Trained as a physical chemist, he always brought that quantitative approach to research questions and used several spectroscopic methods in his research. His broad scientific interests concerned the role of manganese in oxygen evolution, electronic properties of chlorophylls, energy transport in antenna complexes, and electron transport reactions. He was also an enthusiastic teacher, an enormously successful mentor who leaves behind a legion of scientists as his abiding legacy, a lover of music and the outdoors with many interests beyond science, and a dedicated family man with a great sense of humility. In this tribute, we summarize some aspects of Ken Sauer's life and career, illustrated with selected research achievements, and describe his approach to research and life as we perceived it, which is complemented by reminiscences of several current researchers in photosynthesis and other fields. The supporting material includes Ken Sauers's CV and publication list, as well as a list of the graduate students and postdocs he trained and of researchers that spent a sabbatical in his lab.

Cycloartane-type triterpenoids from Combretum quadrangulare Kurz with PCSK9 secretion inhibitory activities.

Nine previously undescribed (1-9) and seven known (10-16) cycloartane-type triterpenoids were isolated and characterized from Combretum quadrangulare Kurz using physicochemical and spectroscopic methods. The absolute configurations of these compounds were determined through modified Mosher's method and quantum chemical calculation of electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectra. Their inhibitory activities against PCSK9 secretion were assessed, and a plausible structure-activity relationship was delineated. Compounds 2, 14, and 15 exhibited notable inhibitory effects on PCSK9 mRNA and protein levels, and significant PCSK9 mRNA inhibition was observed when co-treated with atorvastatin. Compound 15 showed the most potent activity, markedly enhancing LDL uptake compared to the negative control. In vivo pharmacokinetic studies confirmed that compound 15 exhibited higher distribution in the liver than plasma, where PCSK9 is predominantly synthesized. These findings emphasize the potential significance of the cycloartane-type triterpenoid scaffold in discovering PCSK9 inhibitors.

Traditional Use, Chemical Constituents, and Pharmacological Activity of Maytenus elaeodendroides Stem Bark

Plants belonging to the genus Maytenus are members of the Celastraceae family. They have been widely used by different peoples as treatment for curing many diseases. The aim of this study was to explore the anti-inflammatory and antioxidant properties of Maytenus elaeodendroides stem bark extracts, an endemic Cuban plant. The antioxidant activity of four extracts (EtOH, EtOAc, n-BuOH, and diethyl ether/petroleum ether 1:1) was determined using DPPH and FRAP methods. Meanwhile, anti-inflammatory effects by the edema method were induced by croton oil in the mouse ear. The investigated extracts showed radical reduction capacity and prevented ear inflammation at doses of 4 mg/ear. In addition, FIA/ESI/IT/MSn was used to determine the qualitative chemical composition of the EtOAc extract and allowed the identification of five flavan-3-ol monomers, four dimers, and other proanthocyanidin oligomers. From this extract three flavan-3-ol compounds (elaeocyanidin and 4′-O-methylgallocatechin), one of them new (2′-hydroxy-4′-methoxy-epigallocatechin), and a proanthocyanidin dimer (afzelechin-(4β→8)-4′-O-methylepigallocatechin) were isolated and identified by the chromatographic method and spectroscopic techniques, mainly ESI-MS and NMR spectroscopic methods.

Spectroscopic and Molecular Docking Studies on the Influence of Inulin on the Interaction of Sophoricoside with Whey Protein Concentrate

The influence of inulin on the interaction of sophoricoside (Sop) with whey protein concentrate (WPC) was investigated using various spectroscopic methods, including fluorescence spectroscopy (intrinsic fluorescence, synchronous fluorescence, and three-dimensional fluorescence), ultraviolet-visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular docking. Sop was found to quench the intrinsic fluorescence of WPC by a static mechanism, both with and without the addition of inulin, and to enhance the antioxidant capacity of the protein. The addition of inulin slightly increased the binding distance between WPC and Sop, while reducing the number of binding sites from two to one. Non-covalent interactions, predominantly van der Waals forces and hydrogen bonding, were maintained between Sop and the protein. Synchronous fluorescence spectroscopy revealed that Sop prevents the exposure of hydrophobic groups on tryptophan residues, leading to increased surface hydrophilicity of the WPC complex. This aligns with the decreased protein surface hydrophobicity measured by 8-Anilino-1-naphthalenesulfonic acid (ANS) binding assays. With inulin, the overall hydrophobicity of the protein was lower than in the system without inulin, suggesting that both inulin and Sop improve the solubility of WPC. Three-dimensional fluorescence spectral analysis showed a reduction in fluorescence intensity and a red shift in the presence of both Sop and inulin. FTIR spectroscopy indicated a slight increase in the secondary structure ordering of WPC following the addition of both Sop and inulin, suggesting structural stabilization under heating conditions. Molecular docking highlighted the potential for hydrogen bond formation between Sop and WPC.

Thermal Condensation of Dehydrogenation Polymer (DHP) with Xylose

Conventional adhesives used in wood-based panels typically contain volatile organic compounds, including formaldehyde, which can potentially lower indoor air quality and damage human health. Lignin, a natural adhesive present in wood, offers significant advantages over other materials due to its ready availability, renewable nature, rich aromatic rings, and aliphatic and aromatic hydroxyl groups, as well as quinone groups. However, when modified as an adhesive for wood-based panels, lignin suffers from poor water resistance and formaldehyde release. Dehydrogenation polymer (DHP), as a lignin model compound, possesses a structure similar to lignin and excellent water resistance, making it a potential substitute for lignin as a formaldehyde-free adhesive. A DHP-xylose complex was obtained from a condensation reaction between DHP and xylose in hemicellulose in a simulated hot-pressing environment. The feasibility of DHP bonding with hemicellulose components was verified using FT-IR and NMR spectroscopic methods. In addition, the structure of the adduct and condensation process were also studied. DHP and xylose underwent condensation under simulated hot-pressing conditions. Xylose and DHP may be linked by C-C bonds. The thermal condensation of DHP with xylose was investigated. This may contribute to a better understanding of the adhesive bonding process for xylose during hot-pressing and offer support for practical applications.

Terahertz time-domain investigation of atacamite: Spectral analysis and theoretical insights for cultural heritage applications

Spectroscopic methods based on terahertz (THz) radiation can represent an innovative approach in the Cultural Heritage field. Specifically, contemporary and historical pigments can exhibit unique fingerprints. However, despite the high selectiveness of terahertz technique, the origin of spectral characteristics is not often known. In this work, the characteristic terahertz-time-domain spectroscopy spectrum of atacamite is reported in the spectral range 0.1–3.7 THz along with ab initio calculation of lattice dynamics to assess the nature of experimental features. The obtained results enable the acquisition of reliable new data in Heritage sciences, which is essential for developing accurate reference pigment databases.

A New Contribution Confirming the Analogy Between NO+ and Related Aryldiazo Ligands

Abstract. The reaction of the cyclometalated five‐coordinate 16 electron iridium(III) complex [IrCl(H){P(tBu)2C6H4‐k2P,C}{P(tBu)2Ph}] (1) with the diazonium salt [p‐BrC6H4N2]BF4 in dichloromethane at room temperature was investigated. By spontaneous reductive elimination the iridium(I) complex salt trans‐[IrCl(N2C6H4Br‐p){(P(tBu)2)Ph}2]BF4 (2) was obtained in good yield. Therefore, this observed reaction behavior exhibits the diazonium unit as a strong p‐acceptor group and confirms furthermore the analogy between nitrosyl and aryldiazonium ligands. The new compound 2 has been characterized by standard spectroscopic methods and the molecular structure of 2 was determined by a single‐crystal X‐ray diffraction analysis (monoclinic, space group Cc, Z = 4).

Mechanistic characterization of fast dissolving PVP-I powder with multipolymer approaches and investigation on their molecular interaction

Povidone-iodine (PVP-I) is widely used as an antiseptic in medical applications. However, its effectiveness is limited by certain drawbacks, such as low solubility in water and high volatility. Therefore, a formulation of a stable solid PVP-I is desirable. In this study, complexes of molecular PVP-I with polyethylene glycol-polyvinyl alcohol copolymer (PEG-PVA copolymer) were considered water-soluble iodophors. Two different methods were used to prepare the solids: physical mixtures and kneading. The physical characteristics of the obtained solids were evaluated using several spectroscopic methods. The presence of iodine was confirmed by a potentiometric titration and antimicrobial activity was tested. The results showed that the PEG-PVA copolymer interacted with povidone primarily through hydrogen bonding between the hydroxyl part of the PEG-PVA copolymer and the amide part of povidone with an estimated binding energy of 3.2 kcal/mol. The amide groups polarity in povidone made them more likely to form hydrogen bonds with the PEG-PVA copolymer. Also, the protonated pyrrolidone bonded to the triiodide anions by intermolecular hydrogen bonds, which increased PVP-I solubility in water. The kneading method provided a faster dissolution rate than physical mixing and pure PVP-I. The iodine contents were within an acceptable range (10-12%), and the antimicrobial activity proved effective against Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus mutans.

Deciphering Electrocatalytic Hydrogen Production in Water Through a Bioinspired Water-Stable Copper(II) Complex Adorned with (N2S2)-Donor Sites.

Electrocatalytic hydrogen production stands as a pivotal cornerstone in ushering the revolutionary era of the hydrogen economy. With a keen focus on emulating the significance of hydrogenase-like active sites in sustainable H2 generation, a meticulously designed and water-stable copper(II) complex, [Cl-Cu-LN2S2]ClO4, featuring the N,S-type ligand, LN2S2 (2,2'-((butane-2,3-diylbis(sulfanediyl))bis(methylene))dipyridine), has been crafted and assessed for its prowess in electrocatalytic H2 production in water, leveraging acetic acid as a proton source. The molecular catalyst, adopting a square pyramidal coordination geometry, undergoes -Cl substitution by H2O during electrochemical conditions yielding [H2O-Cu-LN2S2]2+ as the true catalyst, showcases outstanding activity in electrochemical proton reduction in acidic water, achieving an impressive rate of 241.75 s-1 for hydrogen generation. Controlled potential electrolysis at -1.2 V vs. Ag/AgCl for 1.6 h reveals a high turnover number of 73.06 with a commendable Faradic efficiency of 94.2 %. A comprehensive analysis encompassing electrochemical, spectroscopic, and analytical methods reveals an insignificant degradation of the molecular catalyst. However, the post-CPE electrocatalyst, present in the solution domain, signifies the coveted stability and effective activity under the specified electrochemical conditions. The synergy of electrochemical, spectroscopic, and computational studies endorses the proton-electron coupling mediated catalytic pathways, affirming the viability of sustainable hydrogen production.