Complexation Research Articles

Catalytic effect of the in-situ rhodium(III) complexes in surfactant medium on the auto-oxidation of 1,2-hydroxyphenylthiourea: A theoretical and experimental study for rhodium(III) sensing

1,2-hydroxyphenylthiourea(HPTU) undergoes auto-oxidation to form an yellow colored dimer. The process of auto-oxidation is enhanced by the presence of trace quantities of transition metal ions and transition metal complexes that act as catalysts. In the current study, catalytic potential of rhodium(III) complexes on the auto-oxidation of 1,2-hydroxyphenylthiourea(HPTU) was studied theoretically using quantum mechanical calculations and experiments were carried out using photometry and fluorometry. DFT studies inferred that [Rh(Py)6]Cl3 showed a better catalytic activity in the dimerization of HPTU. Theoretical studies were subsequently validated through experiments using photometric methods and the range of detection was determined to be 6 ng/mL–100 ng/mL. The detection limit was observed to be 2 ng/mL. Analytical parameters such as pH, reagent concentration, metal ion concentration, appropriate activators and surfactants were established.

Sustainable humification of food waste slurry through thermally activated persulfate oxidation

This study introduces a thermoanalytical approach utilizing sodium persulfate (PS) to expedite the humification of food waste (FW) through advanced oxidation processes (AOPs). The method harnesses heat-induced free radicals to break down complex organic compounds into simpler forms, leading to the formation of humic substances. We conducted an analysis of changes in soluble chemical oxygen demand (SCOD), dissolved organic carbon (DOC), ammonia nitrogen, soluble proteins, and sugars, employing advanced techniques such as three-dimensional fluorescence spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). The findings indicate that the activation of PS at 70°C effectively increases SCOD and DOC levels, converts proteins into soluble forms, and enhances NH4+-N content. This study, which focuses on the utilization of thermal methods, affirms that the thermal activation of persulfate (PS) significantly boosts the humification of food waste (FW), presenting a sustainable approach for waste management and resource recovery.

Role of van der Waals, Electrostatic, and Hydrogen-Bond Interactions for the Relative Stability of Cellulose Iβ and II Crystals.

Naturally occurring cellulose Iβ with its characteristic parallel orientation of cellulose chains is less stable than cellulose II, in which neighboring pairs of chains are oriented antiparallel to each other. While the distinct hydrogen-bond patterns of these two cellulose crystal forms are well established, the energetic role of the hydrogen bonds for crystal stability, in comparison to the van der Waals (vdW) and overall electrostatic interactions in the crystals, is a matter of current debate. In this article, we investigate the relative stability of celluloses Iβ and II in energy minimizations with classical force fields. We find that the larger stability of cellulose II results from clearly stronger electrostatic interchain energies that are only partially compensated for by stronger vdW interchain energies in cellulose Iβ. In addition, we show that a multipole description of hydrogen bonds that includes the COH groups of donor and acceptor oxygen atoms leads to consistent interchain hydrogen-bond energies that account for roughly 70% and 75% of the interchain electrostatics in celluloses Iβ and II, respectively.

Preparation and Antifungal Properties of Cyclopropyl Derivatives of 3-Aminoquinazolin-4(3H)-one and Salicylal Schiff Base Nickel(II) Chelate Complex

N-substituted 2-cyclopropyl-3-R-quinazoline-4()-ones [R: NH2 (1), N=CH(2-hydroxyphenyl) (2)] and Ni(II) chelate compound of 2-cyclopropyl-3-[(Z)-(2-hydroxybenzylidene)amino]quinazoline-4(3H)-one (3) were synthesized and their structures and properties were characterized using X-ray diffraction data, computational optimization, 1H and 13C NMR, IR spectroscopy, and diffuse reflectance spectra. Compounds 1 and 2 are monoclinic (space group P21/n). Unit cell parameters (a, b, c) are 9.2529; 4.7246; 22.3460 Å and 10.2811; 4.6959; 30.972 Å for 1 and 2, respectively. Nickel(II) chelate compound crystallizes in an orthorhombic crystal system (space group Pbca). Unit cell parameters (a, b, c) for 3 are 26.5010; 14.8791; 8.904975 Å, respectively. Schiff base 2 in the crystalline state exhibits two rotary isomers in a molar ratio of 1:3, among which only a minor component as a bidentate ligand can form compound 3 with Ni(II) ion. Nickel(II) ion in 3 is coordinated by N donor atoms and deprotonated O atoms of Schiff base ligands to form square-planar chelate node NiN2O2. All synthesized compounds revealed high antifungal activity against bread mold (Mucor mucedo).

Crown-like Biodegradable Lipids Enable Lung-Selective mRNA Delivery and Dual-Modal Tumor Imaging In Vivo.

Systemic mRNA delivery to specific cell types remains a great challenge. We herein report a new class of crown-like biodegradable ionizable lipids (CBILs) for predictable lung-selective mRNA delivery by leveraging the metal coordination chemistry. Each CBIL contains an impressive crown-like amino core that coordinates with various metal ions such as Zn2+ and further regulates the in vivo organ-targeting behavior of lipid nanoparticles (LNPs). The representative CBIL (Zn-9C-SCC-10)-formulated LNPs could exclusively deliver mRNA to the lung after systemic administration. Notably, following intravenous administration of 0.2 mg kg-1 Cre mRNA, Zn-9C-SCC-10 LNPs enabled the highly efficient gene editing of all lung epithelial and endothelial cells up to 43 and 61%, respectively, outperforming the current state-of-the-art LNPs in lung epithelial cell delivery. Moreover, compared to DLin-MC3-DMA LNPs with the addition of cationic lipid (DOTAP), our approach yielded a 44.6-fold enhancement in pulmonary mRNA expression and significantly improved biosafety in vivo. Taking advantage of paramagnetic gadolinium ion, Gd-12C-SCC-10 LNPs allowed the potent mRNA delivery to cancer cells and successfully illuminated lung tumors by magnetic and bioluminescent dual-mode imaging, facilitating the early discovery and diagnosis of lung cancer. This work will open a new avenue to rationally design predictable LNPs, as well as address the major challenges of mRNA delivery to specific cells in the lung tissues for treating a wide variety of diseases.

A Review: Recent Advances in Chemistry and Applications of 2,4-Dihydroxybenzaldehyde Oxime and Its Transition Metal Complexes

This review presents a comprehensive overview of the recent advances in the chemistry and applications of 2,4-dihydroxybenzaldehyde oxime (DHBO) and its transition metal complexes. DHBO, characterized by its unique hydroxyl and oxime functional groups, has gained significant attention due to its versatile reactivity and potential applications across various fields, including pharmaceuticals, catalysis, and environmental science. Recent synthetic methodologies, including microwave-assisted techniques and green chemistry approaches, have improved the efficiency and sustainability of DHBO production. The formation of transition metal complexes with DHBO has been a focal point of research, revealing enhanced catalytic properties and biological activities compared to the free ligand. These complexes have shown promise in organic synthesis, particularly in oxidation and reduction reactions, as well as in drug development, exhibiting antimicrobial and anticancer properties. Furthermore, the potential of DHBO and its metal complexes in environmental remediation, particularly in removing heavy metals and pollutants, underscores their significance in addressing contemporary environmental challenges. This review also provides current knowledge on the synthesis, characterization, and applications of DHBO and its transition metal complexes, highlighting their importance in both academic research and industrial applications. By elucidating the multifaceted roles of DHBO, this work aims to pave the way for future research and innovation in this promising area of study.

Transition Metal Complexes of Turmeric Schiff Base: A New Avenue for the Development of Antioxidant, Anti‐Inflammatory, and Preliminary Anticancer Therapies via In Silico, In Vitro, and In Vivo Assessments

ABSTRACTIn the current study, Knoevenagel condensates mediated by ultrasound were created using cinnamaldehyde and physiologically active curcumin. These Knoevenagel condensates have been reacted with 4‐aminoantipyrene to create curcumin Schiff bases. The octahedral geometry of the synthesized transition metal complexes is verified by a range of analytical methods and spectroscopic techniques. It is interesting to note that viscosity tests against calf thymus‐DNA and UV–visible absorption titration are used to confirm the synthetic drugs intercalative binding effectiveness. VLS3D online program was utilized to examine the properties of SWISS ADME. The experimental validation of antioxidant and anti‐inflammatory activity demonstrates that theoretical expectations align with the experimental findings. The minimum inhibitory concentration values of the synthesized complexes show that they are more effective against microbes than ligand. Density functional theory simulations were performed at the B3LYP/6–31G(d) level to examine the complexes' thermodynamic stability and physiological accessibility. Every synthetic molecule has been docked against the bovine serum albumin 3v03 enzyme.

AABBA Graph Kernel: Atom-Atom, Bond-Bond, and Bond-Atom Autocorrelations for Machine Learning.

Graphs are one of the most natural and powerful representations available for molecules; natural because they have an intuitive correspondence to skeletal formulas, the language used by chemists worldwide, and powerful, because they are highly expressive both globally (molecular topology) and locally (atom and bond properties). Graph kernels are used to transform molecular graphs into fixed-length vectors, which, based on their capacity of measuring similarity, can be used as fingerprints for machine learning (ML). To date, graph kernels have mostly focused on the atomic nodes of the graph. In this work, we developed a graph kernel based on atom-atom, bond-bond, and bond-atom (AABBA) autocorrelations. The resulting vector representations were tested on regression ML tasks on a data set of transition metal complexes; a benchmark motivated by the higher complexity of these compounds relative to organic molecules. In particular, we tested different flavors of the AABBA kernel in the prediction of the energy barriers and bond distances of the Vaska's complex data set (Friederich et al., Chem. Sci., 2020, 11, 4584). For a variety of ML models, including neural networks, gradient boosting machines, and Gaussian processes, we showed that AABBA outperforms the baseline including only atom-atom autocorrelations. Dimensionality reduction studies also showed that the bond-bond and bond-atom autocorrelations yield many of the most relevant features. We believe that the AABBA graph kernel can accelerate the exploration of large chemical spaces and inspire novel molecular representations in which both atomic and bond properties play an important role.

Eco-friendly Synthesis, Characterization, and Antimicrobial Evaluation of Transition Metal (II) Complexes with Thiophene-Derived Tridentate (S N N Donor) Heterocyclic Schiff Base Ligand

Eco-friendly Synthesis, Characterization, and Antimicrobial Evaluation of Transition Metal (II) Complexes with Thiophene-Derived Tridentate (S N N Donor) Heterocyclic Schiff Base Ligand

Alkali cation-π interactions in aqueous systems, modulating supramolecular stereoisomerism of nanoscopic metal-organic capsules

Contrary to common chemical intuition, cation-π interactions can persist in polar, aqueous reaction solutions, rather than in dry non-coordinative solvent systems. This account highlights how alkali ion-π interactions impart distinctive structure-influencing supramolecular forces that can be exploited in the preparation of nanoscopic metal-organic capsules. The incorporation of alkali ions from polar solutions into molecular pockets promotes the assembly of otherwise inaccessible capsular entities whose structures are distinctive to those of common polyoxovanadate clusters in which {V=O} moieties usually point radially to the outside, shielding the molecular entities. The applied concept is exemplified by homologous {V20} and {V30} cages, composed of inverted, hemispherical {V5O9} units. The number and geometrical organization of these {V5O9} sub-units in these cages are associated with prevailing cation-π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi$$\\end{document} interactions and competing steric effects. The stereoisomers of these resulting nano-sized objects are comparable to Alfred Werner-type structural isomers of simple mononuclear complexes in-line with fundamental coordination chemistry principles.

Insights into antimalarial and anti-tuberculosis activities of Schiff base transition metal complexes: molecular docking and ADMET profiling approaches

Insights into antimalarial and anti-tuberculosis activities of Schiff base transition metal complexes: molecular docking and ADMET profiling approaches

The Application of Machine Learning in Doping Detection.

Detecting doping agents in sports poses a significant challenge due to the continuous emergence of new prohibited substances and methods. Traditional detection methods primarily rely on targeted analysis, which is often labor-intensive and is susceptible to errors. In response, machine learning offers a transformative approach to enhancing doping screening and detection. With its powerful data analysis capabilities, machine learning enables the rapid identification of patterns and features in complex compound data, increasing both the efficiency and the accuracy of detection. Moreover, when integrated with nontargeted metabolomics, machine learning can predict unknown metabolites, aiding the discovery of long-lasting biomarkers of doping. It also excels in classifying novel compounds, thereby reducing false-negative rates. As instrumental analysis and machine learning technologies continue to advance, the development of rapid, scalable, and highly efficient doping detection methods becomes increasingly feasible, supporting the pursuit of fairness and integrity in sports competitions.

The coordination chemistry and anticancer activity of organo-ruthenium(II), -iridium(III) and -rhodium(III) complexes with sulfonyl-substituted thiourea ligands.

Some half-sandwich compounds with a variety of ligands and metal centres have shown promising anticancer activity. Herein we report a series of reactions between the sulfonylthiourea ligands p-TolSO2NHC(S)NHPh, EtSO2NHC(S)NHPh and CH3SO2NHC(S)NHPh and [(η6-p-cymene)RuCl2]2, [(η6-arene)RuCl2(PR3)] (arene = benzene or p-cymene), [Cp*MCl2(PR3)] or [Cp*RhCl2]2 (M = Ir(III), Rh(III)), Cp* = η5-pentamethylcyclopentadienyl, PR3 = triphenylphosphine (PPh3), tris(2-cyanoethyl)phosphine (tcep) and 1,3,5-triaza-7-phosphaadamantane (pta) and their corresponding piano stool complexes. Single crystal X-ray diffraction structure determinations indicated that the resulting linkage isomer of the complex, i.e., proximal (coordination via S,N(sulfonated) placing the sulfonyl group near the coordination sphere) or distal (coordination via S,N(non-sulfonated), placing the sulfonyl group away from the coordination sphere), is directly related to the steric bulk around the metal centre. Proximal to distal isomerisation of the complex [(η6-p-cymene)Ru{p-TolSO2NC(S)N(PPh3)}] (1aL1) was observed by 1H and 31P{1H} NMR spectroscopy. DFT calculations suggested this to be the result of the conversion from the initially formed kinetically favourable to the thermodynamically favourable isomer. Computational investigation of non-covalent interactions using the reduced density gradient also revealed a chalcogen bond present between the thiourea sulfur and sulfonyl oxygen atoms of complex 1aLa. The in vitro antiproliferative activity of several complexes was determined against human cancer cells, which revealed a correlation between potency and lipophilic properties of the ancillary ligands for a series of Ru(II) p-cymene complexes.

Assessment of the Physicochemical Properties of Ultrafine Particles (UFP) from Vehicular Emissions in a Commercial Parking Garage: Potential Health Implications.

Vehicular emissions are a major culprit in the rise of urban air pollution. The particulate matter (PM) emitted from vehicular sources includes primarily ultrafine particles (UFPs) with aerodynamic diameters less than 0.1 µm (PM0.1) and is linked to adverse respiratory and cardiovascular health effects. Despite this knowledge, few exposure assessment studies exist that detail the physicochemical properties of PM in parking garages. In this study, airborne PM emitted by vehicles in a parking garage of a hospital in New Jersey was sampled, during winter and summer seasons, and physicochemically characterized. The results indicate that the mass concentrations of the UFPs in the garage were 2.51 µg/m3 and 3.59 µg/m3, respectively. These UFPs contained a large percentage of elemental carbon and toxic elements. They also contained polycyclic aromatic hydrocarbons (PAHs), having deleterious health effects. An inhalation particle modeling revealed that 23.61% of these UFPs are deposited in the pulmonary region of the lung, translating to a dose of 10.67 µg for winter and 15.25 µg for summer, over a typical 40 h work week. These high deposited levels of UFPs and their complex chemistry levels further warrant the need for toxicological assessment of UFPs related to vehicular emissions.

A Mature Tool to Address New Challenges: Harnessing Coordination Chemistry for The Sustainable Copper Recovery from Industrial and E‐Waste in The Age of Energy Transition

Copper is arguably one of the most strategic metal for the energy transition, particularly in the shift from fossil fuel‐based engines to sustainable and renewable energy sources, with related and broader electrification efforts. While global copper mineral resources are far from depleted, their uneven distribution poses significant supply risks, especially in regions like Europe. In 2023, the European Union (EU) recognized this risk by designating copper as a strategic raw material (SRM), highlighting the need for innovative copper recovery processes. Copper recovery from industrial and electronic waste has been approached through various methods, primarily categorized into pyrometallurgy and solvo‐ and hydrometallurgy. The latter offers greater tunability and potential for sustainability, particularly when leveraging coordination chemistry. This review focuses on the most promising hydrometallurgical processes for copper recovery from industrial and e‐waste (i.e., electronic waste), with a special emphasis on the role of coordination chemistry in supporting these methods. We posed particular focus on the adaptability and versatility of the coordination chemistry‐based processes to the highly heterogenous composition of the copper‐containing wastes.

Recent Developments in the Metal-Catalyzed Synthesis of Nitrogenous Heterocyclic Compounds.

Metal-catalyzed cyclization reactions have become a powerful and efficient approach for the stereoselective construction of both carbocyclic and heterocyclic ring systems. Transition metal complexes, with their ability to activate and selectively functionalize organic substrates, have revolutionized various areas of synthetic chemistry. This review highlights recent advancements in metal-catalyzed cyclization reactions, especially in the synthesis of nitrogen-containing heterocycles like imidazoles, pyridines, pyrimidines, and indoles. These advancements have significantly impacted fields such as natural product synthesis, pharmaceuticals, functional materials, and organic electronics. Novel catalytic systems, ligand designs, and reaction conditions continue to expand the capabilities of these reactions, driving further the progress made in synthetic organic chemistry. This review provides a comprehensive overview of recent research.

Preparing Ruthenium Complex-Contained DaTp COFs via π-π Interactions for Visible-Light-Driven Photocatalytic Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) is a crucial energy carrier with growing significance in sustainable energy systems. Covalent organic frameworks (COFs) have recently emerged as promising materials for efficient H2O2 photosynthesis, while transition-metal complexes are recognized for their efficacy as molecular photocatalysts in H2O2 production. This study introduces a novel π-π interaction strategy to immobilize ruthenium complexes into COFs, using DaTp COF as a model system. This approach significantly enhances the photocatalytic activity for H2O2 production, achieving an initial rate of 3276 μmol g-1 h-1 without using scavengers under visible-light irradiation (λ > 420 nm). Notably, incorporating ruthenium complexes optimizes the oxygen reduction reaction pathways, shifting from a less efficient four-electron process to a more efficient two-electron process. Density functional theory calculations further reveal that ruthenium complexes not only broaden the light absorption spectrum of the COF but also increase water affinity, directly contributing to H2O2 generation. These findings offer a strategic framework for designing and enhancing COFs in H2O2 photosynthesis applications.

Self-Exfoliated Guanidinium Covalent Organic Nanosheets as High-Capacity Curcumin Carrier.

Drug administration is commonly used to treat chronic wounds but faces challenges such as poor bioavailability, instability, and uncontrollable release. Existing drug delivery platforms are limited by chemical instability, poor functionality, complex synthesis, and toxic by-products. Presently, research efforts are focused on developing novel drug carriers to enhance drug efficacy. Guanidinium Covalent Organic Nanosheets (gCONs) offer promising alternatives due to their high porosity, surface area, loading capacity, and ability to provide controlled, sustained, and target-specific drug delivery. Herein, we successfully synthesized self-exfoliated gCONs using a Schiff base condensation reaction and embedded curcumin (CUR), a polyphenolic pleiotropic drug with antioxidant and anti-inflammatory properties, via the wet impregnation method. The BET porosimeter exhibited the filling of gCON pores with CUR. Morphological investigations revealed the formation of sheet-like structures in gCON. Culturing human dermal fibroblasts (hDFs) on gCON demonstrated cytocompatibility even at a concentration as high as 1000 µg/mL. Drug release studies demonstrated a controlled and sustained release of CUR over an extended period of 5 days, facilitated by the high loading capacity of gCON. Furthermore, the inherent antioxidant and anti-inflammatory properties of CUR were preserved after loading into the gCON, underscoring the potential of CUR-loaded gCON formulation for effective therapeutic applications. Conclusively, this study provides fundamental information relevant to the performance of gCONs as a drug delivery system and the synergistic effect of CUR and CONs addressing issues like drug bioavailability and instability.

The Human Cornea: Unravelling Its Structural, Chemical and Biochemical Complexities.

The cornea, the transparent part of the anterior eye, is vital for light refraction and vision. This review examines the intricate chemical and biochemical interactions essential for maintaining corneal transparency and highlights significant advancements in corneal biology. The cornea comprises five layers: the epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium, each contributing uniquely to its structure and function. The epithelium, maintained by limbal stem cells, serves as a barrier and interacts with the tear film to maintain ocular surface health. The stroma, abundant in organized collagen fibrils and regulated by proteoglycans, is crucial for corneal clarity and biomechanical integrity, while the endothelium regulates corneal hydration and nutrition. Recent imaging advances have improved visualization of these molecular structures, enhancing our understanding of collagen organization and cross-linking. Proteoglycans such as decorin and lumican regulate collagen spacing and hydration, directly influencing corneal clarity. Biochemical processes within the cornea involve signaling molecules, growth factors, and cytokines, which are essential for wound healing, inflammation, and injury response. Despite progress, questions remain regarding corneal wound healing mechanisms, the impact of oxidative stress, and the roles of microRNAs. This review synthesizes recent discoveries to advance our understanding of corneal physiology and biochemical functions.

Zwitterionic 2‐Phosphaethene‐thiolates [(LC)P=CS(LC/P)]+ as PCS Building Blocks (LC = NHC, LP = PR3)

The zwitterionic compounds [(LC)P=CS(LC/P)]+ (3+, LC = NHC, LP = PR3), featuring cationic substituents at the phosphorus and carbon atoms, are synthesized as their triflate salts at a multi‐gram scale from the reaction of Lewis base adducts of CS2, namely LC/P–CS2 (4), with a combination of [(LCP)4][OTf]4 (1[OTf]4) and Ph3P. The feasibility of using 3+ as PCS building blocks is showcased in their reactions with representative electrophiles (MeOTf) and nucleophiles (MesMgBr, Ph3PCH2), leading to selective functionalization of the PCS core at the S‐ and P‐terminus, respectively. Additionally, it is reported that 3+ can function as ambident nucleophiles with AgOTf (2 equivalents), affording unprecedented linear coordination polymer [Ag2(OTf)3‐μ2:κP,κS–((LC)P=CS(PCy3))]+ (6b), where the PCS moiety acts as a bridging ligand in transition metal complexes for the first time. Reduction of 3+ facilitates the cleavage of the P‐ and C‐bound substituents leading to the formation of the [PCS]– anion. Moreover, cycloaddition reactions of 3+ with 1[OTf]4 are shown to selectively yield five‐ and eight‐membered polyphosphorus heterocycles. Preliminary results suggest the possibility of activating the C–S bond in [(LC)P=CS(LC)]+, resulting in the formation of [(LC)P=C(LC)–P(LC)][OTf]2, 12[OTf]2, which may serve as a synthon for the PCP unit in future studies.