Catalytic Complex Research Articles

Nanozyme-Shelled Microcapsules for Targeting Biofilm Infections in Confined Spaces.

Bacterial infections in irregular and branched confinements pose significant therapeutic challenges. Despite their high antimicrobial efficacy, enzyme-mimicking nanoparticles (nanozymes) face difficulties in achieving localized catalysis at distant infection sites within confined spaces. Incorporating nanozymes into microrobots enables the delivery of catalytic agents to hard-to-reach areas, but poor nanoparticle dispersibility and distribution during fabrication hinder their catalytic performance. To address these challenges, a nanozyme-shelled microrobotic platform is introduced using magnetic microcapsules with collective and adaptive mobility for automated navigation and localized catalysis within complex confinements. Using double emulsions produced from microfluidics as templates, iron oxide and silica nanoparticles are assembled into 100-µm microcapsules, which self-organize into multi-unit, millimeter-size assemblies under rotating magnetic fields. These microcapsules exhibit high peroxidase-like activity, efficiently catalyzing hydrogen peroxide to generate reactive oxygen species (ROS). Notably, microcapsule assemblies display remarkable collective navigation within arched and branched confinements, reaching the targeted apical regions of the tooth canal with high accuracy. Furthermore, these nanozyme-shelled microrobots perform rapid catalysis in situ and effectively kill biofilms on contact via ROS generation, enabling localized antibiofilm action. This study demonstrates a facile method of integrating nanozymes onto a versatile microrobotic platform to address current needs for targeted therapeutic catalysis in complex and confined microenvironments.

Sustainable methods for producing food-derived bioactive compounds

Background: Pursuing alternative starting materials has gained significant importance in the food and drug industries, driven by the global shift towards sustainable and renewable resources. Terpenes, naturally occurring hydrocarbons derived from plants, present a promising solution due to their abundant availability and range of physiological activities, including antioxidant, anti-inflammatory, antimicrobial, and anticancer properties. Objective: This study aims to develop a waste-free synthesis methodology for functionalizing limonene and myrcene, two notable terpenes, through Atom Transfer Radical Reactions (ATRR). The objective is to achieve high yields and purities while enhancing the therapeutic potential of these compounds and adhering to green chemistry principles. Methods: A catalytic complex of Cu(I)Br and dimethyl sulfoxide (DMSO) was used to facilitate the coupling of limonene and myrcene with various trichloroacetic acid derivatives. Reactions were performed at 80°C for 90 minutes, and products were purified by column chromatography. The synthesized compounds were characterized using Gas Chromatography-Mass Spectrometry (GC-MS) and Nuclear Magnetic Resonance (NMR). Microbiological analyses were conducted using the disk-diffusion method, and statistical analyses were performed to assess the reliability of the experiments. Results: The ATRR methodology enabled the efficient functionalization of limonene and myrcene, achieving high yields and purities. The best yield for limonene was 70%, and for myrcene, 82%, both using trichloroacetonitrile. The Cu(I) catalytic system showed dualistic biological effects, with 3% concentration exhibiting strong bactericidal and fungicidal activity, while 0.03% promoted growth. These results demonstrate the potential of the methodology and the catalytic system for bioactive compound synthesis and agricultural applications. Conclusion: This study demonstrates the viability of ATRR for efficiently functionalizing limonene and myrcene, achieving high yields and purities. The synthesized compounds show promise for pharmaceutical development. The dual antibacterial and antifungal activities of the Cu(I) catalytic system also suggest potential applications in wastewater reutilization. Future work should explore the biological effects and environmental impact of this process. Keywords: Terpenes, ATR reactions, Green Chemistry, Bioactive compounds, Therapeutic potential.

Behind the scenes of green chemistry: Glories and shadows of atom transfer radical polymerization environmental impact (E-factor)

The paper presents the evaluation of environmental impact (E-factor) as green chemistry metric, calculated for polymer synthesis via one of the most useful tools of macromolecular chemistry, which is atom transfer radical polymerization (ATRP), belonging to the reversible deactivation radical polymerization (RDRP) techniques. For the first time, experimentally determined polymerization yields were included in the calculation, by analyzing the polymer synthesis process using various organic solvents, different methods of regenerating the catalytic complex (meaning ATRP approach), or using the miniemulsion system as eco-friendly reaction medium and presenting the possibility of effective solvent recovery and reuse. The majority of the values of E-factor were below 16, falling within the scope intended for fine chemicals (5–50). The significant and innovative part of the presented research involves verifying the feasibility of using higher concentrations of the dispersed phase in the case of miniemulsion polymerization (increased to as much as 100 % vs. aqueous phase from a typical 20 %), while the use of recycled water allowed a 3-fold reduction in E-factor value. Polymerization in a miniemulsion environment is also attractive due to its low cost, considering the price of distilled water, which is over 580-fold lower than that of DMSO – a typical organic solvent. These observations allow for the reduction of environmental impact and process cost. Importantly, the observed trends in E-factor changes allowed for the identification of ATRP development directions in line with green chemistry and the circular economy.

Molecular dynamics approach to efficient hydrogen generation process of Co-B catalysts decorating lanthanides (La, Ce, Pr, Nd) supported by flat-sheet and twisted ThMoB4-type graphene from NaBH4 hydrolysis: Insights from non-self-consistent GFN1-xTB method

In this study, the promoter role on highly efficient hydrogen generation productivity and H2 formation mechanisms of Co-B-X catalysts modified by rare earths (X = La, Ce, Pr, Nd) supported by flat-sheet and twisted ThMoB4-type graphene from sodium borohydride (NaBH4) hydrolysis was investigated using molecular dynamics (MD) method based on non-self-consistent tight binding GFN1-xTB Method. The twisted ThMoB4-type graphene layer was constructed by adsorbing of ethylene carbonate (EC) molecule on armchair site of graphene surface with applying of geometric optimization process. The addition of Nd to CoB exhibited to higher H2 release compared to other CoB containing lanthanides (La, Ce and Pr) both flat-sheet and twisted ThMoB4-type graphene. While the number of H2 for Co-B-Nd is 14, the H2 amount is only 8 for Co-B-Ce supported flat-sheet graphene at the end of simulation time. Also, the placing of twisted graphene instead of flat-sheet in the catalytic complex led to about 36 % increase in H2 number for Co-B-Nd. The computational results revealed that the availability of the active sites, such as basicity of catalytic environment related to OH and H species and the mobility of Co atom, played an important role for catalytic activity and performance for H2 production. This work can provide new insight for experimental studies of Co-B-X (X = La, Ce, Pr, Nd) catalysts for hydrogen production in atomic-level and the creation of new hydrogen energy applications and facilitates for H2 generation efficiency.

Synthesis and BSA binding study of the Cu(II) complex and applications of it to enhance catalytic activity for C(Sp2)-H bond functionalization and for the synthesis of polyhydroquinolines

Among the various copper-catalyzed coupling reactions, C–S and C–N bond-forming reactions have carried off plentiful recognition due to their demand in the synthesis of molecules having biological and pharmaceutical impact. Organo-copper complex has an incontestable supremacy over the other catalytic complex due to its low cost and the use of readily accessible and stable ligands. As a consequence and in continuation of our explorative studies in this direction, an efficient and novel organo-copper complex has been synthesized and characterized by spectroscopic (NMR, FT-IR) and single crystal X-ray diffraction (XRD) methods. The synthesized stable metal complex has fascinating physical, chemical, biological and catalytic properties. In the chemical exploration refer to protein-metal interactions; we have often used Bovine Serum Albumin (BSA) protein. The synthesized copper complex has the potential to form coordinate bonds with functional groups present in BSA, together with amino acid residues and the protein backbone. The binding of metal complexes to BSA has outstanding imputation in medicinal chemistry. For enhancement of the catalytic activity of the organo-copper complex, we have evaluated it in carbon-hetero bond formation reactions where it proffered an influential tool for the establishment of C–S and C–N bonds.

Click Chemistry for the Generation of Combination of Triazole Core and Thioether Donor Site in Organosulfur Ligands: Applications of Metal Complexes in Catalysis.

During the last two decades, organosulfur compounds have been used in the field of transition metal catalysis. Some of such compounds are known for their ability to withstand their exposure to air and moisture. These compounds are very important ligands. They may be obtained using simple and smooth modular synthetic protocols which include nucleophilic substitution reactions. The development of click chemistry represents a new era of innovation. It is a lighthouse of reliable and efficient reactions. In recent past, click chemistry has also been applied for the synthesis of such organosulfur ligands specifically suited for the dynamic field of transition metal catalysis. In order to synthesize novel compounds containing sulfur and triazole ring, click chemistry is an advantageous methodology over other approaches. This article covers the general features and uses of this methodology for the development of catalytically active organosulfur compounds. The significant advances in the design of transition metal catalytic systems utilizing such ligands, their use in the catalysis of many chemical transformations are also covered in this article. Effort has also been made to present a comparative overview of the performances of such catalysts vis-à-vis the catalysts designed commonly used ligands. Catalytic performances have been discussed thoroughly in order to identify the impact of ligand architecture on efficacy of the catalyst. Effect of reaction conditions (such as time, temperature etc.) and mechanistic aspects have also been rationalized.

Solar Light CO2 Photoreduction Enhancement by Mononuclear Rhenium(I) Complexes: Characterization and Mechanistic Insights.

The catalytic efficacy of a novel mononuclear rhenium(I) complex in CO2 reduction is remarkable, with a turnover number (TONCO) of 1517 in 3 h, significantly outperforming previous Re(I) catalysts. This complex, synthesized via a substitution reaction on an aromatic ring to form a bromo-bipyridine derivative, L1 = 2-bromo-6-(1H-pyrazol-1-yl)pyridine, and further reacting with [Re(CO)5Cl], results in the facial-tricarbonyl complex [ReL1(CO)3Cl] (1). The light green solid was obtained with an 80% yield and thoroughly characterized using cyclic voltammetry, nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy. Cyclic voltammetry under CO2 atmosphere revealed three distinct redox processes, suggesting the formation of new electroactive compounds. The studies on photoreduction highlighted the ability of the catalyst to reduce CO2, while NMR, FTIR, and electrospray ionization (ESI) mass spectrometry provided insights into the mechanism, revealing the formation of solvent-coordinated complexes and new species under varying conditions. Additionally, computational studies (DFT) were undertaken to better understand the electronic structure and reactivity patterns of 1, focusing on the role of the ligand, the spectroscopic features, and the redox behavior. This comprehensive approach provides insights into the intricate dynamics of CO2 photoreduction, showcasing the potential of Re(I) complexes in catalysis.

A multipurpose organometallic pyridyl Schiff base-modified poly(divinylbenzene) matrix for the catalytic removal of nitrophenols and polycyclic pollutants

Widespread organic pollutants in wastewater include toxic nitrophenols and polycyclic molecules. Here, we aim to develop a single multipurpose catalyst capable of degrading these structurally dissimilar contaminants by preparing a pyridyl Schiff base-functionalized poly(divinylbenzene) porous organic polymer displaying Ag complexes (PDVB-PA@Ag). PDVB-PA@Ag hydrogenated 4-nitrophenol (4-NP) efficiently to valuable and less toxic 4-aminophenol with an optimized reaction rate of 45.4 × 10−3 s−1 and apparent activation energy of only 20.1 kJ mol−1. The same catalyst also readily hydrogenated the isomers of 4-NP as well as nitrophenols with several nitro groups and halogenated nitrophenols with reaction rates ranging from 4.0 to 20.3 × 10−3 s−1. In addition, the multiuse PDVB-PA@Ag was capable of carrying out a second type of reaction and degraded multiple polycyclic dyes commonly found in wastewater including auramine O, basic blue 17, aniline blue, and malachite green through Fenton-like oxidation. PDVB-PA@Ag-based degradation processes for the four toxic dyes evaluated were efficient with pseudo-first order reaction rates varying between 1.2 × 10−2 to 3.7 × 10−2 min−1. By coordinating an array of versatile catalytic complexes on an extensive and stable porous support, PDVB-PA@Ag was made highly performant at completing different essential water-cleaning processes.

A cooperation of ceric ammonium nitrate and N-hydroxyphthalimide in the aerobic oxidation from ketones to lactones/esters: Catalytic characterization and mechanistic investigation

When molecular oxygen is employed as the oxidant in the Baeyer-Villiger reaction, the addition of an excess amount of sacrificial aldehyde/alcohol to generate peroxyacids or peroxides in situ is the most frequently adopted strategy. In this work, we report a sacrifice-free approach to lactone/esters from ketones using molecular oxygen as the oxidant, in which cerium ammonium nitrate and N-hydroxyphthalimide were utilized as the catalysts with a good tolerance to cyclic and aromatic ketones. Experiments have shown that the presence of α-hydrogens in ketone compounds is a critical condition for the reaction, and the 2H labeling experiments demonstrated that the oxidation is initiated via the deprivation of the α-hydrogen of ketone by phthalimide N-oxy radical (PINO), which is significantly different from the Criegee-Intermediate mechanism of traditional BV reaction. And the 18O labeling experiment suggested that NO3− participates in the oxidation of the carbonyl compounds and NO3− could be regenerated by molecular oxygen. The redox process of cerium and the structure of the catalytic complex were also illustrated by the EPR and XRD characterization. Meanwhile, cerium ammonium nitrate was proved to be capable recycle although its reactivity was decreased after two cycles. The unprecedented mechanism for the synthesis of lactone/ester was hoped to provide a new prospect in the academic study and industrial manufacture.

Dual C(sp3)-H and C(sp2)-H Activation of 8-Methylquinoline N-Oxides: A Route to Access C7-H Bond.

A Pd(II)-catalyzed regioselective dual C(sp3)-H/C7(sp2)-H activation and annulation of 8-methylquinoline N-oxides with maleimide has been accomplished. The use of N-oxide as a weak directing group under Pd(II)-complex catalysis activates the initial C(sp3)-H and triggers a relayed, second C7(sp2)-H activation. The dual C-H bond activation, [3 + 2]-annulation, facile introduction and removal of the directing group, substrate scope, and functional group diversity are the important practical features.

Pbp4 provides transpeptidase activity to the FtsW-PbpB peptidoglycan synthase to drive cephalosporin resistance in Enterococcus faecalis.

Enterococci exhibit intrinsic resistance to cephalosporins, mediated in part by the class B penicillin-binding protein (bPBP) Pbp4 that exhibits low reactivity toward cephalosporins and thus can continue crosslinking peptidoglycan despite exposure to cephalosporins. bPBPs partner with cognate SEDS (shape, elongation, division, and sporulation) glycosyltransferases to form the core catalytic complex of peptidoglycan synthases that synthesize peptidoglycan at discrete cellular locations, although the SEDS partner for Pbp4 is unknown. SEDS-bPBP peptidoglycan synthases of enterococci have not been studied, but some SEDS-bPBP pairs can be predicted based on sequence similarity. For example, FtsW (SEDS)-PbpB (bPBP) is predicted to form the catalytic core of the peptidoglycan synthase that functions at the division septum (the divisome). However, PbpB is readily inactivated by cephalosporins, raising the question-how could the FtsW-PbpB synthase continue functioning to enable growth in the presence of cephalosporins? In this work, we report that the FtsW-PbpB peptidoglycan synthase is required for cephalosporin resistance of Enterococcus faecalis, despite the fact that PbpB is inactivated by cephalosporins. Moreover, Pbp4 associates with the FtsW-PbpB synthase and the TPase activity of Pbp4 is required to enable growth in the presence of cephalosporins in an FtsW-PbpB-synthase-dependent manner. Overall, our results implicate a model in which Pbp4 directly interacts with the FtsW-PbpB peptidoglycan synthase to provide TPase activity during cephalosporin treatment, thereby maintaining the divisome SEDS-bPBP peptidoglycan synthase in a functional state competent to synthesize crosslinked peptidoglycan. These results suggest that two bPBPs coordinate within the FtsW-PbpB peptidoglycan synthase to drive cephalosporin resistance in E. faecalis.

Sonochemical Isomerization of [5,6]-open Adducts of C60 Fullerene with Camphor Derivatives into [6,6]-closed Ones

Abstract: For the first time, a sonochemical method has been developed for the structural rearrangement of [5,6]-open mono- and poly adducts of fullerene C60 containing spirocyclic fragments of camphor analogs into [6,6]-closed isomers. The isomerization reaction occurs with quantitative yield under mild conditions: 1 hour at room temperature. A probable mechanism of sonochemical isomerization has been proposed. Mono- and poly adducts of C60 fullerene containing spirocyclic fragments of camphor analogues were obtained in the reaction of metal complex catalysis by the Pd(acac)2–2PPh3–4Et3Al system with the participation of fullerene and diazo compounds.

N‐heterocyclic carbene complexes RuII(arene) and their application as ROMP catalysts, antioxidant and anticancer agents

N‐Heterocyclic carbenes (NHCs) play an important role in metal complex catalysis and stabilisation, providing stability under non‐inert conditions and a high σ‐donor capacity. They are crucial ligands for the synthesis of organometallic compounds like RuII‐complexes, which can operate as very active catalysts for a variety of chemical transformations and functionalizations. RA(Ruthenium‐arene)NHC complexes, known for their piano‐stool structure, stabilise Ru(II) oxidation by occupying three ruthenium coordination sites with a η6‐coordinated arene ligand. The development of dual‐acting RuII‐arene complexes has sparked increased interest in their catalytic and biological properties. Because of their broad spectrum, metal complexes can give distinct mechanisms of pharmacological action than organic drugs. This study aimed to explore the impact of ligand amphiphilicity and counterion on bioactivity, designing a family of compounds with the NHC ligand bearing an ester moiety and switching the wingtip substituent from methyl to benzyl units. All synthesized compounds were tested in norbornene ROMP, a benchmark reaction for RuII potential catalysts and as anticancer and antioxidant compounds.

A Radical Strategy for the Alkylation of Amides with Alkyl Halides by Merging Boryl Radical-Mediated Halogen-Atom Transfer and Copper Catalysis.

Amide alkylation is a fundamental process in organic chemistry. However, the low nucleophilicity of amides means that divergent coupling with alkyl electrophiles is often not achievable. To circumvent this reactivity challenge, individual amine synthesis followed by amidation with standard coupling agents is generally required. Herein, we demonstrate a radical solution to this challenge by using an amine-borane complex and copper catalysis under oxidative conditions. While borohydride reagents are generally used as reducing agents in ionic chemistry, their conversion into amine-ligated boryl radicals diverts their reactivity toward halogen-atom transfer. This enables the conversion of alkyl halides into the corresponding alkyl radicals for amide functionalization via copper catalysis. The process is applicable to the N-alkylation of primary amides employing unactivated alkyl iodides and bromides, and it was also showcased in the late-state functionalization of both complex amide- and halide-containing drugs.

Organocatalyzed iodine-mediated reversible-deactivation radical polymerization via photoinduced charge transfer complex catalysis

Organocatalyzed iodine-mediated reversible-deactivation radical polymerization via photoinduced charge transfer complex catalysis

Enantioselective N-H Bond Insertion Reaction of Anilines Enabled by Ruthenium and Chiral Phosphoric Acid Cooperative Catalysis.

The enantioselective carbene insertion into N-H bonds of anilines has been realized by cooperative catalysis of ruthenium complexes and chiral phosphoric acids, providing the expected α-aryl glycines in moderate to good yields with high enantioselectivity. Typically, by slightly modifying the reaction conditions, this approach allows the N-H bond insertion reaction to be effective for both α-aryl and α-alkyl diazoacetates for the first time with high enantioselectivity (up to 96% and 95% ee, respectively).

Biocatalyst mediated green approach for 1,8-dioxo-octahydroxanthenes: SCXRD, Hirshfeld analysis and DFT studies as inhibitors of HIV reverse transcriptase

AIDS, caused by human immunodeficiency virus (HIV) is persistent on being one among the deadliest disease of all time. It destroys the immune system of the body and there is currently no effective cure for this. In this regard, in continuation to our studies on green catalysts, more efficient, constructive, and environmentally sustainable protocols for the synthesis of xanthene and its derivatives as HIV Reverse Transcriptase inhibitors were developed with the use of biocatalyst via baker's yeast that explores a viable approach on expanding environmental challenges and enlightens the superiority and exclusivity of this protocol. The current approach manifests numerous notable advantages that include ease of preparation, handling and benignity of the catalyst, low cost, green reaction conditions, facile workup, excellent yields (87–96 %) with extreme purity. The title compounds were docked on the crystal structure of a catalytic complex of HIV-1 reverse transcriptase (PDB: 1RTD). The C-score values achieved in the range 6.68–3.05 suggest that docking analysis was propitious signifying the review of all the forces of interaction between the ligand and the protein. The crystal studies and DFT analysis of compound 3d correlate the optimized geometrical features with empirically accessible XRD data.

Exploring the Reactivity and Stability of Transition Metal Coordination Complexes in Catalysis

Transition metallic coordination complexes assume a pivotal part in diverse reactant cycles in view in their capacity to paintings with an volume of substance modifications. The reactivity and balance of those complexes are earnest elements that have an impact on their functionality and software in synergist applications. This hypothetical offers a format of the key additives affecting the reactivity and balance of transition steel coordination complexes in catalysis. The stability of metal complex is addressed by double unmistakable views like thermodynamic and dynamic strong characteristics. The dating among's balance and reactivity of coordination composites portrayed in the assessment. These evaluation moreover selects the components manipulating the steadiness of steel complexes just like that through metallic particles, ligands, bonding among metal particles and ligands, etc. Likewise, strategies open on behalf of affirmation of stability coefficients passed comprehensively.

Metal complex catalysis of initiated oxidation of hydrocarbons and alcohols: features of inhibition

Metal complex catalysis of initiated oxidation of hydrocarbons and alcohols: features of inhibition

Postsynthetic Modification of Amine-Functionalized MIL-101(Cr) Metal-Organic Frameworks with an EDTA-Zn(II) Complex as an Effective Heterogeneous Catalyst for Hantzsch Synthesis of Polyhydroquinolines.

The present work aims at preparing the EDTA-Zn(II) complex-supported on the amine-functionalized MIL-101(Cr) MOF-as a new and effective heterogenized catalyst. The optimization of the hydrothermal process shows that 120 °C is the best condition to grow the MIL-101(Cr)-NH2 MOF crystals. Moreover, regarding the use of the postsynthetic modification (PSM) method, hexadentate EDTA was grafted on this support via a simple aminolysis process before further coordinating it with Zn ions to create the corresponding Zn(II) catalytic complex. The catalytic activity of this compound was then investigated in the context of a one-pot synthesis of polyhydroquinolines. This approach has a number of advantages including the following: the use of a solvent that is not hazardous, applying a porous catalyst that is inexpensive, secure, and recyclable; rapid reaction times, high levels of efficiency, and the simplicity of MOF catalyst separation. Accordingly, the process in question can be given the label of "green chemistry".