Reaction Of Ligand Research Articles

Enhancing the Reactivity of an Aromatic cyclo-P5 Ligand via Electrophilic Activation.

Electrophilic activation of the aromatic cyclo-P5 ligand in [Cp*Fe(h5-P5)] is demonstrated to drastically enhance its reactivity towards weak nucleophiles. Unprecedented functionalized, contracted as well as complexly aggregated polyphosphorus compounds are accessed utilizing [Cp*Fe(h5-P5Me)][OTf] (A), highlighting the great potential of this underexplored mode of reactivity. Addition of carbenes to A affords novel 1,2- or 1,1-difunctionalized cyclo-P5 complexes [Cp*Fe(h4-P5(1-L)(2-Me)][OTf] (L=IDipp (1), EtCAAC (2), IiPr (3b)) and [Cp*Fe(h4-P5(1-IiPr)(1-Me)][OTf] (3a). For the first time, the much smaller IMe4 leads to the contraction of the cyclo-P5 ligand and formation of [Cp*Fe(h4-P4(1-IMe)(4-Me)] (4). DFT calculations shed light on the delicate mechanism of this type of reaction, which is reinforced by the experimental identification of key intermediates. Even the comparably weak nucleophile IDippCH2 reacts with A to form [Cp*Fe(h4-P5(1-IDippCH2)(1/2-Me)][OTf] (6a/b), highlighting its explicitly more reactive nature. Moreover, exposure of A to IDippEH (E = N, P) leads to a unique aggregation reaction affording [{Cp*Fe}2{m2,h4:3:1‑P10Me2(IDippN)}][OTf] (8) and [{Cp*Fe}2{m2,h4:1:1:1‑P11Me2(IDipp)}][OTf] (9), respectively.

Ligand Noninnocence in β-Diketiminate and β-Diketimine Copper Complexes.

Metal-ligand cooperative systems have a long precedent in catalysis, with the classification depending on the site of substrate bond cleavage and formation and on redox state changes. Recently, our group reported the participation of a β-diketiminate ligand in chemical bonding to heterocumulenes such as CO2 and CS2 by tricopper complexes, leading to cooperative catalysis. Herein, we report the reactivity of these copper clusters, [Cu3EL]- (E = S, Se; L = tris(β-diketiminate) cyclophane ligand), toward other electrophiles, viz. alkyl halides and Brønsted acids. We identified a family of ligand-functionalized complexes, Cu3EL (R) (R = primary alkyls), and a series of disubstituted products, Cu3EL (R)2, through single-crystal X-ray diffraction, mass spectrometry, and infrared and UV-visible spectroscopy. As part of mechanistic studies on these alkylation reactions, we evaluated the acid-base reactivity of these complexes and the influence of the backbone substitution on the reduction potential. Implications of these findings for ligand noninnocence and the relevance of the metal core as a cofactor for the ligand's reactivity are discussed.

Bifunctional Ligands: Evaluating the Role of Acidic Protons in the Secondary Coordination Sphere.

To evaluate bifunctional ligand reactivity involving NH acidic sites in the secondary coordination sphere, complexes where the proton has been substituted with a methyl group (NMe) are often investigated. An alternative strategy involves substitution of the NH group for an O. This contribution considers and compares the merits of these approaches; the synthesis and characterization of cationic square-planar Rh carbonyl complexes bearing diprotic bispyrazole pyridine ligand L1, and the bis-methylated pyrazole pyridine ligand L1Me are described. The syntheses and characterization of the novel monoprotic pyrazole isoxazole pyridine ligand L2 and aprotic bisisoxazole pyridine ligand L3, and their corresponding Rh carbonyl complexes are also described. Comparison of the CO stretching frequencies of the four Rh complexes suggest that substitutions of NH with NMe, as well as with O, lead to significant electronic differences. These electronic differences result in different reactivities with respect to ligand addition/substitution of the Rh carbonyl complexes. Overall, the data suggest that electronic differences arising due to the NH substitutions can be significant and should be considered when the NH group is substituted in investigations of the participation of the NH proton in a reaction.

Redox Synergy: Enhancing Gas Sensing Stability in 2D Conjugated Metal–Organic Frameworks via Balancing Metal Node and Ligand Reactivity

AbstractTwo‐dimensional conjugated metal–organic frameworks (2D c‐MOFs) have emerged as promising candidates in gas sensing, owing to their tunable porous structure and conductivity. Nevertheless, the reported gas sensing mechanisms heavily relied on electron transfer between metal nodes and gas molecules. Normally, the strong interaction between the metal sites and target gas molecule would result poor recovery and thus bad recycling property. Herein, we propose a redox synergy strategy to overcome this issue by balancing the reactivity of metal sites and ligands. A 2D c‐MOF, Zn3(HHTQ)2, was prepared for nitrogen dioxide (NO2) sensing, which was constructed from active ligands (hexahydroxyltricycloquinazoline, HHTQ) and inactive transition‐metal ions (Zn2+). Substantial characterizations and theoretical calculations demonstrated that by utilizing only the redox interactions between ligands and NO2, not only high sensitivity and selectivity, but also excellent cycling stability in NO2 sensing could be achieved. In contrast, control experiments employing isostructural 2D c‐MOFs with Cu/Ni metal nodes exhibited irreversible NO2 sensing. Our current work provides a new design strategy for gas sensing materials, emphasizing harnessing the redox activity of only ligands to enhance the stability of MOF sensing materials.

Redox Synergy: Enhancing Gas Sensing Stability in 2D Conjugated Metal-Organic Frameworks via Balancing Metal Node and Ligand Reactivity.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have emerged as promising candidates in gas sensing, owing to their tunable porous structure and conductivity. Nevertheless, the reported gas sensing mechanisms heavily relied on electron transfer between metal nodes and gas molecules. Normally, the strong interaction between the metal sites and target gas molecule would result poor recovery and thus bad recycling property. Herein, we propose a redox synergy strategy to overcome this issue by balancing the reactivity of metal sites and ligands. A 2D c-MOF, Zn3(HHTQ)2, was prepared for nitrogen dioxide (NO2) sensing, which was constructed from active ligands (hexahydroxyltricycloquinazoline, HHTQ) and inactive transition-metal ions (Zn2+). Substantial characterizations and theoretical calculations demonstrated that by utilizing only the redox interactions between ligands and NO2, not only high sensitivity and selectivity, but also excellent cycling stability in NO2 sensing could be achieved. In contrast, control experiments employing isostructural 2D c-MOFs with Cu/Ni metal nodes exhibited irreversible NO2 sensing. Our current work provides a new design strategy for gas sensing materials, emphasizing harnessing the redox activity of only ligands to enhance the stability of MOF sensing materials.

Activation of SO2F2 at a Rhodium PNP Pincer Complex: Ligand Supported S-F Bond Cleavage to Generate NSO2F Derivatives.

The κ2-(P,N)-phosphine ligand precursor NH(CH2CH2PCy2)2 can be used for the synthesis of the rhodium(I) complex [Rh(CO){ĸ3-(P,N,P)-Cy2PC2H4NHC2H4PCy2}][Cl] (1). The deprotonated complex [Rh(CO){ĸ3-(P,N,P)-Cy2PC2H4NC2H4PCy2}] (2) shows a cooperative reactivity of the PNP ligand in the activation reaction of SO2F2 to yield the rhodium fluorido complex trans-[Rh(F)(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2 (3) by S-F bond cleavage. It is remarkable that no reaction was observed when 3 was treated with hydrogen sources e. g. dihydrogen, organosilicon compounds such as triethylsilane or TMS-CF3 and different fluorine sources such as SF4 or Selectfluor®. However, the treatment of complex 3 with XeF2 in the presence of CsF resulted in the formation of the unique fluorido rhodium(III) complex cis,trans-[Rh(F)3(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2 (4). In the presence of pyridine(HF)X or BF3 the fluorido complex 3 converted into the dicationic complexes [Rh(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2[XF]2, X=HF (5) or BF3 (6), respectively.

Zn-Ti oxo cluster photoresists for EUV Lithography: Cluster structure and lithographic performance

Low reflectivity of multilayer mirror–induced low efficiency of existing extreme ultraviolet lithography (EUVL) has triggered the search for photoresists with heightened sensitivity. For this purpose, considerable research has focused on elements with high extreme ultraviolet (EUV) absorption, leading to considerable advancements. Solubility alteration, often resulting from ligand variations after exposure, is influenced by the cluster structure, markedly impacting lithography sensitivity. Herein, three Ti-based metal clusters, Ti6O4(OEt)8(OMc)8 (T-2), Zn2Ti4O4(OiPr)2(OMc)10 (TZ-1), and Zn4Ti2O2(OAc)2(OBu)2(OMc)10 (TZ-2), are designed and synthesized to elucidate the effects of the structure on lithography. These mixed metal–oxo clusters derived from Ti6O4(OR)8(OOCR)8 and stabilized by identical ligands exhibit structural diversity. The increase in the number of zinc atoms results in marked alterations in the oxo core, thereby triggering alterations in ligand coordination modes. These variations confer metal clusters with different solubility and lithographic properties. Analysis of the photochemical reaction mechanism and theoretical calculations reveal a reactive tridentate ligand coordination mode that considerably improves lithography sensitivity. Therefore, changing the ligand coordination mode by designing a mixed metal–oxo core holds promise for discovering new photoresists for EUV lithography.

Nitrous oxide and dinitrogen complexes as intermediates in the decomposition of metal carbonyl nitrosyls: The triruthenium system

The stability of some metal carbonyl nitrosyls is limited by the oxidation of CO groups by adjacent NO groups to eliminate CO2. Theoretical studies show how intermediates in such processes can be trapped as molecular species using the central Ru3 unit found in the stable and experimentally known Ru3(CO)10(µ-NO)2. Two stages of such NO reduction by adjacent CO ligands have been identified in the Ru3 system. The first stage, as demonstrated by conversion of Ru3(CO)10(µ-NO)2 to the N2O complex Ru3(CO)9(µ3-N2O), involves attack of the oxygen atom of an NO group on the carbon atom of an adjacent CO group to eliminate CO2. This leaves a reactive nitride ligand that can couple with a second NO group to form an N2O complex. The oxygen atom on such an N2O ligand can convert an adjacent CO group to CO2 thereby leaving behind a metal dinitrogen complex.

Synthesis of a new Zn-phthalocyanine, photophysical, photochemical, and sono-photochemical properties and DFT studies

In recent years cancer has become a global problem and burden to the health system. Photodynamic therapy (PDT) and sonodynamic therapy (SDT) are promising alternatives for cancer treatment. It is very important to use phthalocyanines as sensitizers in such treatments. In this study, a new type of Zn-phthalocyanine compound (2) peripherally substituted with 4-Hydroxy-7-methoxyquinoline was synthesized and characterized, and its photodynamic and sono-photodynamic efficiencies were examined. Additionally, the electronic and spectroscopic properties of the compounds were calculated theoretically using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods. The effect of the solvent on the reactivity of the compounds was examined by the Conductive-Like Polarizable Continuum Model (CPCM). The results have indicated that singlet oxygen quantum yield has increased in the sono-photochemical study (ΦΔ=0.98) compare to the photodynamic study (ΦΔ=0.70). Experimental and theoretical study results show that the reactivity of the new ligand increases with Zn metal.

Borate ligand derived from CS2 unveiling ruthenium dithioformate and trithia-borinane complexes

The reactivity of κ2-N,S-chelated ruthenium borate complexes, [Ph3P(κ2-N,S-L)Ru{κ3-H,S,S′-H2B(L)2}], (L = C5H4NS, C7H4NS2) 1 and 3 with borate ligand derived from CS2 has been investigated. The thermolysis of [Ph3P(κ2-N,S-C5H4NS)Ru{κ3-H,S,S′-H2B(C5H4NS)2}], 1 with Na[BH3(SCHS)] led to the formation of ruthenium dithioformate complexes, [PPh3(κ3-H,S,S′-H2B(C5H4NS)}Ru{(η2-SCHS)}], trans-2 and [PPh3(κ3-H,S,S′-H2B(C5H4NS)}Ru{(η2-SCHS)}], cis-2. Further, to study the reactivity of the same borate ligand derived from CS2, we have performed the reaction of [Ph3P(κ2-N,S-C7H4NS2)Ru{κ3-H,S,S′-H2B(C7H4NS2)2}], 3 with Na[BH3(SCHS)] that yielded ruthenium dithioformate, [Ph3P(κ2-N,S-C5H4NS)Ru{(η2-SCHS)}], cis-4 and 1,3,5-trithia-2-borinane, [PPh3Ru{κ3-H,S,S′-H2B(NC7H4S2)2}]{(SCH2)2SBH}], 5 complexes. All these studies show that cis-4 is analogous to trans-2 and cis-2. The solid-state X-ray structure of 5 shows that the ruthenium center is stabilized by diborate, phosphine and six-membered ruthenacycle [RuSBNCS] ring that is fused with a {C2S3B} ring. The synthesized complexes have been thoroughly characterized by various spectroscopic techniques and single-crystal X-ray diffraction analysis of trans-2, cis-2 and 5. Density functional theory (DFT) calculations further provided an insight into the electronic structures of the complexes.

Investigating the impact of solvation on p-Phenylenediamine - 2-Amino pyrimidine - Formaldehyde Terpolymer (P2APF) ligand's reactivity and drug suitability for malaria treatment: Insights from experimental and quantum calculations

This study aims at investigating the drug potential of p-Phenylenediamine – 2-Amino Pyrimidine – Formaldehyde terpolymer (P2APF) ligand against drug resistant Plasmodium falciparum. Plasmodium falciparum, an embodiment of cunning among malaria parasites, thrives in regions plagued by rampant mosquito transmission, subpar vector control, and limited access to effective treatments. To this end, this study explored the structural properties of the p-Phenylenediamine – 2-Amino Pyrimidine – Formaldehyde terpolymer (P2APF) ligand, (comprising p-Phenylenediamine, 2-Aminopyrimidine, and Formaldehyde) as a drug potent ligand against the common proteins coding for malaria infection. Various spectroscopic techniques such as FT-IR, UV–visible, and NMR (1H & 13C) spectroscopy were employed both experimentally and theoretically. Additionally, the ligand's surface morphology was investigated using scanning electron microscopy. To comprehend the influence of solvation, theoretical investigations utilizing density functional theory (DFT) at the B3LYPD(BJ)/6-311G++G (2d,2p) level were conducted in DMSO, water, and methanol solvents. The results from the frontier molecular orbital (FMO) analysis provided valuable insights into the electronic properties and solvation effects of P2APF. Specifically, the calculated energy gap of 3.671 eV for P2APF_methanol and 3.672 eV for P2APF_DMSO suggested these solvents as promising environments for reactivity and interactions. Molecular docking studies unveiled the most notable binding affinity between P2APF and the 5UMB chaperone protein receptor, exhibiting a binding affinity of -7.3 kcal/mol on serine and aspartic acid residues, with an average bond distance of 2.25 Å. This robust protein-ligand interaction signifies the promising potential of the P2APF ligand in targeting this specific receptor, thereby combating drug-resistant strains of Plasmodium falciparum for the present and the future.

Synthesis and characterization of resorcinol based trisazo reactive dye ligand and its metal chelates for application on cellulosic fabric

The purpose of this research was to innovate novel trisazo reactive dyestuffs from 1, 2, 4-acid (the 1-amino-2-naphthol-4-sulphonic acid), the resorcinol derivativatized chemical substance, the vinyl sulphone para ester, and their transition metal chelates iron (II), nickle (II), copper (II), and zinc (II). For the synthesis, resorcinol in an alkaline medium was coupled to diazotized 1, 2, 4-acid (1-amino-2-naphthol-4- sulphonic acid) to create the 1, 2, 4-acid (the 1-amino-2-naphthol-4- sulphonic acid)- resorcinol mono-azo dye ligand. The 1, 2, 4-acid (1-amino-2-naphthol-4- sulphonic acid)- resorcinol mono-azo dye ligand was passed through coupling with the diazotized vinyl sulphone para este in an alkaline medium to generate tris-azo reactive dyestuff. Metal chelates of reactive dyestuffs have also been generated using 3d transition metals, namely iron, zinc, iron, copper, as well as nickel. The metallization of the synthesized monoazo dye ligands with sulphate salts of iron, nickel, copper, and zinc, as well as the coupling reaction with diazotized vinyl sulphone para ester resulted hot brand novel vinyl sulfone-type trisazo fiber reactive dyes. To evaluate how successfully the novel synthesized dyestuffs dyed cotton fabric, these were applied to cotton fabric in one percent, three percent, and six percent (stock) solutions relative to the weight of cotton fabric, and were examined for their characteristics. These showed excellent light fastness, rub fastness, and wash fastness when applied to cotton fabric. Analytical data and spectroscopic techniques allying optical studies thereby UV-Visible spectroscopy and FTIR spectral interpretation were utilized to confirm the constituents of whole innovative, novel synthesized tris-azo reactive dye substances. Maximum synthesized tris-azo reactive dyestuffs found to have large values of their wash fastness 4 and above on the grey scale, and light fastness 4 and above on the blue scale, respectively, when dyed on cotton cloth. A comparative study of these dyes was also done with existing standards, the pantone color system. The dye adhesion, reactivity, dissolution, as well as stabilizing qualities were all outstanding, indicating that the fabric was well dissolved. Such artificial trisazo reactive dyestuffs were transferred attractively onto the colored cotton cloth, evenly distributed, well permeated into the fiber, and fastened. Consequently, tris-azo reactive dyestuff ligand, and its metal chelates were appraised accomplished wonderfully, while colored cotton cloth. These dyestuffs will further benefit the creation of innovative industrial items. Consequently, this in-house production of creative resorcinol-based dyestuffs will also usher in a futuristic era of investigation for the country’s economic advancement, and in industrialization.

Hexakis(urea-O)iron Complex Salts as a Versatile Material Family: Overview of Their Properties and Applications.

Due to their Fe- and N-containing reactive urea ligand content, the hexakis(urea-O)iron(II) and hexakis(urea-O)iron(III) complexes were found to be versatile materials in various application fields of industry and environmental protection. In our present work, we have comprehensively reviewed the synthesis, structural and spectroscopic details, and thermal properties of hexakis(urea-O)iron(II) and hexakis(urea-O)iron(III) salts with different anions (NO3-, Cl-, Br- I-, I3-, ClO4-, MnO4-, SO42-, Cr2O72-, and S2O82-). We compared and evaluated the structural, spectroscopic (IR, Raman, UV-vis, Mössbauer, EPR, and X-ray), and thermogravimetric data. Based on the thermal behavior of these complexes, we evaluated the solid-phase quasi-intramolecular redox reactions of anions and urea ligands in these complexes and summarized the available information on the properties of the resulting simple and mixed iron-containing oxides. Furthermore, we give a complete overview of the application of these complexes as catalysts, reagents, absorbers, or agricultural raw materials.

Acetylene ligands stabilize atomically dispersed supported rhodium complexes under harsh conditions

Facile sintering of atomically dispersed supported noble metal catalysts at catalytically relevant temperatures, particularly under reducing conditions, poses a challenge for their practical applications. Some ligands, such as carbonyls, aid in improving the stability at the expense of severely suppressing the catalytic activity. Here, we demonstrate that substitution of the carbonyl ligands with reactive acetylene ligands can maintain the atomic dispersion of the supported mononuclear rhodium complex under harsh reducing conditions (>573 K), as confirmed by in-situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies. In contrast, the supported rhodium carbonyl complex aggregates into nanoclusters under identical conditions. Furthermore, our results indicate that the acetylene ligands provide this anti-sintering ability while retaining the hydrogenation activity.

Ligand Desorption and Fragmentation in Oleate-Capped CdSe Nanocrystals under High-Intensity Photoexcitation.

Semiconductor nanocrystals (NCs) offer prospective use as active optical elements in photovoltaics, light-emitting diodes, lasers, and photocatalysts due to their tunable optical absorption and emission properties, high stability, and scalable solution processing, as well as compatibility with additive manufacturing routes. Over the course of experiments, during device fabrication, or while in use commercially, these materials are often subjected to intense or prolonged electronic excitation and high carrier densities. The influence of such conditions on ligand integrity and binding remains underexplored. Here, we expose CdSe NCs to laser excitation and monitor changes in oleate that is covalently attached to the NC surface using nuclear magnetic resonance as a function of time and laser intensity. Higher photon doses cause increased rates of ligand loss from the particles, with upward of 50% total ligand desorption measured for the longest, most intense excitation. Surprisingly, for a range of excitation intensities, fragmentation of the oleate is detected and occurs concomitantly with formation of aldehydes, terminal alkenes, H2, and water. After illumination, NC size, shape, and bandgap remain constant although low-energy absorption features (Urbach tails) develop in some samples, indicating formation of substantial trap states. The observed reaction chemistry, which here occurs with low photon to chemical conversion efficiency, suggests that ligand reactivity may require examination for improved NC dispersion stability but can also be manipulated to yield desired photocatalytically accessed chemical species.

Curated phytochemicals of Annona muricata modulate proteins linked to type II diabetes mellitus: Molecular docking studies, ADMET and DFT calculation

One of the medicinal herbs utilized in treating diabetes traditionally is Annona muricata. This work investigates the effect of phytochemicals from A. muricata on the therapeutically important protein targets associated with type II diabetes mellitus (T2DM) using a computational approach. Compounds (Phytochemicals) previously identified in A. muricata were docked against proteins of interest to find therapeutic hit compounds. The stability of the ligand-protein complexes was examined after selecting proteins that bind well with the discovered hits, and ADMET properties of the ligands were also predicted to determine their toxicity and drug-likeness. In addition to studying the compounds' softness, hardness, electron affinity, and electrostatic potential, the Schrödinger material science Jaguar fast engine was used to study their frontier molecular orbital (FMO). The targets aldose reductase (ALR), 11beta-hydroxysteroid dehydrogenase type 1 (11-HSD1), and diacylglycerol O-acyltransferase 1 (DGAT1) exhibited the highest binding affinities from the early screening of compounds against fifteen (15) proteins linked with T2DM. While eight (8) phenolic compounds of the plants had comparatively high docking scores with 11β-HSD1 and ALR, seven (7) acetogenins had good binding affinities with DGAT1. These top-scoring compounds exhibited considerable ADMET profiles. Additionally, the phenolic compounds that are considered as hits adhered to the Lipinski rule of 5 and can be thought of as potential drug candidates. Genistein and kaempferol are the most reactive ligands in terms of quantum mechanics. The information from this study could be used to create an alternative anti-diabetic drug with better efficacy.

Thiol‐Free p‐Type Colloidal Quantum Dot for Efficient Broadband Optoelectronics

Colloidal quantum dots (CQDs) are promising semiconductors for optoelectronic applications owing to their bandgap tunability and solution processability. Historically, ethanedithiol has been widely employed as a surface ligand to form a p‐type CQD layer via a layer‐by‐layer process. However, the limited control of p‐type characteristics reduces the device performance, and the high reactivity of ligand and processing solvents degrade the underlying layer. In this study, a thiol‐free p‐type CQD is demonstrated by creating native p‐type CQDs during the synthesis process. Sulfurization of PbS CQD results in p‐type properties that enable the avoidance of any further thiol‐ligand treatment process. Further, alternative surface passivation of the sulfurized CQD using halide ligand yields a robust, p‐type, morphologically uniform, and trap‐suppressed film. The developed CQD film is then employed as a hole‐transporting layer (HTL) for both broadband solar cells and photodetectors. The resulting CQD devices exhibit improved performance with a 65.7% increase in photovoltaic efficiency and a 1.7‐fold improvement in responsivity for infrared photodetection. The devices also demonstrate higher ambient stability, retaining 85% of the initial performance after 1,000 hr owing to the uniform top HTL morphology, indicating the potential of the new p‐type layer to be utilized in various emerging optoelectronics.

Synthesis, antimicrobial activity, DFT-calculation, and docking of 4-(1,3,4-thiadiazol-2-yl)-containing polysubstituted pyrroles

A series of new 4-(1,3,4-thiadiazol-2-yl)-containing polysubstituted pyrroles 3 a-k has been synthesized by a preparative convenient method from ethyl 5-chloro-4-formyl-1H-pyrrole-3-carboxylates 1 a-e, which were selectively transformed into the corresponding polysubstituted pyrrole-4-carboxylic acids 2 а-е using sodium hypochlorite as an oxidizer. Further, they were transformed into the target compounds with a high yield using the cyclocondensation with N-mono- or N,N-disubstituted thiosemicarbazides in the boiling phosphorus trichloroxide. As seen from the screening of antimicrobial activity, the synthesized compounds exhibit the inhibiting and bactericide activity against some bacteria and fungi. The highest activity has been established for the compounds 3 a, c, e-h, j against the strain Klebsiella pneumoniae (МІС=31.25 µg/mL). The calculated HOMO energy level proves that the compound 3 с is the most reactive ligand for the interaction with a protein receptor. The molecular docking data show that the compound 3 h has the highest affinity to the ThiM Klebsiella pneumoniae kinase.

Enabling Nucleophilic Reactivity in High-Spin Fe(II) Imido Complexes: From Elementary Steps to Cooperative Catalysis.

ConspectusTransition metal complexes featuring an M═NR bond have received great attention as critical intermediates in the synthesis of nitrogen-containing compounds. In general, the properties of the imido ligand in these complexes are dependent on the nature of the metal center. Thus, the imido ligand tends to be nucleophilic in early transition metal complexes and electrophilic in late transition metal complexes. Nonetheless, the supporting ligand can have a dramatic effect on its reactivity. For example, there are sporadic examples of nucleophilic late transition metal imido complexes, often based on strongly donating supporting ligands. Building on these earlier works, in this Article, we show that the imido ligand in a low-coordinate high-spin bis(carbene)borate Fe(II) complex is able to access previously unknown reaction pathways, ultimately leading to new catalytic transformations. We first focus on the synthesis, characterization, and stoichiometric reactivity of a highly nucleophilic Fe(II) imido complex. The entry point for this system is the intermediate-spin three-coordinate Fe(III) imido complex, which is generated from the reaction of an Fe(I) synthon with an organic azide. Alkali metal reduction leads to a series of M+ (M = Li, Na, K) coordinated and charge-separated (M = K(18-C-6)) high-spin Fe(II) imido complexes, all of which have been isolated and fully characterized. Combined with the electronic structure calculations, these results reveal that the alkali ions moderately polarize the Fe═N bond according to K+ ≈ Na+ < Li+. As a result, the basicity of the imido ligand increases from the charged separated complex to K+, Na+, and Li+ coordinated complexes, as validated by intermolecular proton transfer equilibria. The impact of the counterion on imido ligand reactivity is demonstrated through protonation, alkylation, and hydrogen atom abstraction reactions. The counterion also directs the outcome of [2 + 2] reactions with benzophenone, where alkali coordination facilitates double bond metathesis. Building from here, we describe how the unusual nucleophilicity of the high-spin Fe(II) imido complex revealed in stoichiometric reactions can be extended to new catalytic transformations. For example, a [2 + 2] cycloaddition reaction serves as the basis for the catalytic guanylation of carbodiimides under mild conditions. More interestingly, this complex also exhibits the first ene-like reactivity of an M═NR bond in reactions with alkynes, nitriles, and alkenes. These transformations form the basis of catalytic alkyne and nitrile α-deuteration and pKa-dictated alkene transposition reactions, respectively. Mechanistic studies reveal the critical role of metal-ligand cooperativity in facilitating these catalytic transformations and suggest the new avenues for transition metal imido complexes in catalysis that extend beyond classical nitrene transfer chemistry.

Atomically dispersed zeolite-supported rhodium complex: Selective and stable catalyst for acetylene semi-hydrogenation

Supported rhodium catalysts are known to be unselective for semi-hydrogenation reactions. Here, by tuning the electronic structure of supported mononuclear rhodium sites determined by the metal nuclearity and the electron-donor properties of the support, we report that atomically dispersed HY zeolite-supported rhodium with reactive acetylene ligands affords a stable ethylene selectivity > 90 % for acetylene semi-hydrogenation at 373 K and atmospheric pressure, even when ethylene is present in a large excess over acetylene. Infrared and X-ray absorption spectra and measurements of rates of the catalytic reaction complemented with calculations at the level of density functional theory show how the catalyst performance depends on the electronic structure of the rhodium, influenced by the support as a ligand that is a weak electron donor.