Carboxylic Function Research Articles

Docking-based analysis and modeling of the activity of bile acids and their synthetic analogues on large conductance Ca2+ activated K channels in smooth muscle cells.

The objective of this study was to perform docking-based analysis of bile acid binding on the protein complex of channels and to derive neural network that predicts the influence of bile acids and their synthetic analogues on the activity of BK(Ca) channels in smooth muscle cells based on descriptors for bile acids and their synthetic analogues and on their already published activities using patch-clamp techniques. Ligands for molecular docking were optimized using computer routine for minimization of energy by using the force field MMFF94 via Chem3D 15.0 and ligands and protein channel complex were prepared in AutoDockTools 1.5.6. AutoDock Vina 4.0 software was used for blind docking; processing and verification of the obtained results was performed via Discovery Studio 4.0. Neural network was derived using descriptors for bile acids and their synthetic analogues and their already published activities on calcium-activated K+ channels in smooth muscle cells (ChemDraw Professional 15.0, Dragon 6 software). Molecular docking was performed for: lithocholic acid, deoxycholic acid, 5β-cholanoic acid, 3β-hydroxi-5β-cholanoic acid, henodeoxycholic acid, ursocholic acid and α-muricholic acid. Neural network model Multiple layer perceptron is derived, having 0.9259 training performances and 0.3673 test performances, training error 0.0073 and test error 0,1607. Model was tested for henodeoxycholic, ursocholic and α-muricholic acid, and internal validation of the model is performed. Molecular docking suggested that the pharmacophore for maximizing the activity of BK(Ca) channels in the steroid skeleton of bile acids is the C3 quasi-axial α-OH group and the C24 carboxyl function. Derived neural network model successfully predicted activities of tested bile acids on Ca2+ activated K+ channels in smooth muscle cells.

Natural inspired ligustrazine-based SLC-0111 analogues as novel carbonic anhydrase inhibitors

Ligustrazine is the principle bioactive alkaloid in the widely-used Chinese herb Chuan Xiong rhizome. Herein, a series of novel derivatives has been designed as human carbonic anhydrases inhibitors (hCAIs) starting from the natural product Ligustrazine inserted as a tail instead of the 4-fluorophenyl tail of SLC-0111, a front-runner selective hCA IX inhibitor currently in clinical trials as antitumor/antimetastatic agent. Other derivatives were designed via incorporation of different linkers, of amide and ester type, or incorporation of different zinc anchoring groups such as secondary sulfamoyl and carboxylic acid functionalities. The newly designed molecules were prepared following different synthetic pathways, and were assessed for their inhibitory actions against four isoforms: the widespread cytosolic (hCA I and II), and the transmembrane tumor-related (hCA IX and XII). The primary sulfonamides efficiently inhibited the target hCA IX and hCA XII in the nanomolar range (KIs: 6.2–951.5 nM and 3.3–869.3 nM, respectively). The most selective hCA IX inhibitors 6c and 18 were assessed for their potential anticancer effects, and displayed anti-proliferative activity against MCF-7 cancer cell line with IC50s of 11.9 and 36.7 μM, respectively. Molecular modelling studies unveiled the relationship between structural features and inhibitory profiles against the off-target hCA II and the target, tumor-related isoforms hCA IX and XII.

Thermogravimetric Studies for the Incineration of an Anion Exchange Resin Laden with Short- or Long-Chain PFAS Compounds Containing Carboxylic or Sulfonic Acid Functionalities in the Presence or Absence of Calcium Oxide

Thermogravimetric Studies for the Incineration of an Anion Exchange Resin Laden with Short- or Long-Chain PFAS Compounds Containing Carboxylic or Sulfonic Acid Functionalities in the Presence or Absence of Calcium Oxide

Combustion of pelletized freshwater macroalgae and pine blends using a fixed bed reactor

Freshwater macroalgae are an underutilized group of ubiquitous algae with greater yield potentials than most terrestrial energy crops, but whose combustion characteristics are not thoroughly understood. This effort compared the combustion of pelletized 100% pine and macroalgae-containing solid fuel mixtures (90%/10% and 75%/25% pine/macroalgae) using a fixed bed co-current reactor. Macroalgae increased pellet density as its protein and calcium content promoted hydrogen bonding and cross-linked the carboxylic acid functionality of polysaccharides. In addition, higher concentrations of freshwater macroalgal biomass required a greater air flow rate to achieve the mixing required for combustion. Since the macroalgae had a higher level of fuel nitrogen and fuel sulfur, emissions of nitrogen and sulfur oxides largely grew with an increasing proportion of this fuel. Overall, pelletized macroalgae can be co-combusted with woody biomass and its pre-treatment (water-rinsing and modulating cultivation conditions) can reduce or eliminate drawbacks found in the harvested naturally-occurring algal material.

Diminished Fluid Transport through Carbon Nanochannels Induced by COOH Functionalization: Implications for Nanofiltration and Oil Recovery

Fluid transport on confined systems is a subject of theoretical and technological interest. For instance, remarkable high flow rates have been obtained in carbon nanochannels (CNs) which cannot be predicted by standard macroscopic theories. Natural rocks, which are at the heart of the shale hydrocarbon revolution, may also exhibit similar properties as the porous structure is mainly at the nanoscale and is carbon rich. Among other differences with CNs, the surfaces are not atomically smooth, as they have organic functional groups anchored on their inner porous surfaces. In this work, we assess the effects of carboxylic functionalization of the nanochannel surfaces on fluid transport. We consider water and methane as representative cases for polar/non-polar fluids and also mixtures of them. We find that the presence of only a few carboxylic groups on the CN causes a large reduction of flow rates for all fluids considered due to the associated geometrical distortion. However, for water, the hydrophilicity induced by the carboxylic functionalization causes not only a dramatic reduction in flow rates but also structural changes in which COOH groups act as nucleation centers for water droplets. Implications of our results show that the flow rates depend on the O/C ratio of the nanochannel, which is a measure of kerogen maturity. The relationship between rock permeability and maturity may provide a way to identify high conductive zones for hydrocarbon recovery. Another application is the possible use of chemical additives to enhance hydrocarbon flow on kerogen-rich rocks. The presence of a small amount of scattered organic functional groups in the nanochannel helps to distribute water molecules along the nanochannel walls, opening a path for hydrocarbon to flow.

Design and synthesis of an oral prodrug alalevonadifloxacin for the treatment of MRSA infection

Levonadifloxacin is a parenteral anti-MRSA benzoquinolizine antibacterial drug recently launched as, EMROK in India to treat acute bacterial skin and skin structure infections (ABSSSI) in hospitalized patients. As a step down therapy an oral form of levonadifloxacin with comparable PK/PD was needed because the levonadifloxacin exhibits very poor oral absorption. To improve the drugability in terms of oral absorption a pro-drug approach was evaluated. Structurally levonadifloxacin provides two sites amenable for ester or amide formation, a carboxyl function of benzoquinolizine pharmacophore and hydroxyl group on piperidine side chain. Several aliphatic, aromatic and amino acid esters of C-2 carboxylic acid, C-4-hydroxyl piperidine and double esters at both C-2, C-4 positions were synthesized. The cleavage of prodrugs was studied in vitro as well as in animal models to access their suitability as prodrug function. Among C-2 carboxylic ester prodrugs, daloxate (WCK 2320) showed highest cleavage in serum as well as in liver enzyme; however its stability in aqueous solution was unfavorable. In contrast, most of the esters at the hydroxyl group like propionyl ester (WCK 2305) and amino acid esters such as l-alanine (WCK 2349), l-valine (WCK 2630) were cleaved readily releasing active drug. Thus, indicating C-4-hydroxyl piperidine was amenable site for enzymatic cleavage over esters of C-2 carboxylic acid. Additionally, amino acid esters provided an opportunity to make salt, facilitating improved aqueous solubility. Methanesulfonate salt of l-alanine ester of levonadifloxacin (WCK 2349) was successfully developed and launched as oral prodrug alalevonadifloxacin (EMROK-O).

Oxidative Depolymerization of Alkaline Lignin from Pinus Pinaster by Oxygen and Air for Value-Added Bio-Sourced Synthons.

In this work, an efficient 3-step process targeting the chemical modification and purification of lignin oligomers from industrial alkaline lignin is described. The oxidative depolymerization process of alkaline lignin with O2 or Air pressure, without use of metal catalyst, led to the production of two fractions of lignin oligomers named ‘precipitated lignin’ and ‘hydrosoluble lignin’ with 40% and 60% yield, respectively. These fractions were characterized with a wide range of methods including NMR spectroscopy (31P, 2D-HSQC), SEC (in basic media), FTIR. NMR analyses revealed the presence of carboxylic acid functions at a ratio of 1.80 mmol/g and 2.80 mmol/g for the precipitated and hydrosoluble lignin, respectively, values much higher than what is generally found in native lignin (between 0.2 and 0.5 mmol/g). SEC analyses revealed the formation of low molar masses for the precipitated (2200 g/mol) and hydrosoluble fractions (1500 g/mol) in contrast to the alkaline lignin (3900 g/mol). It is worth noting that the hydrosoluble fraction of lignin is soluble in water at any pH. Both processes (oxygen and air) were successfully scaled up and showed similar results in terms of yield and functionalization.

Synthesis and Characterization of Lignin-graft-poly(ethylene brassylate): a Biomass-Based Polyester with High Mechanical Properties

Lignin is an important biopolymer that can be used as a raw material to produce functional polymers due to its abundance, low price, sustainability, and high concentration of aromaticity. However, lignin modification is not well understood or characterized, limiting its potential as a new sustainable raw material. The biopolymer lignin can be integrated with aliphatic polyesters to produce new biomass-based biodegradable polymers. Among various aliphatic polyesters, poly(ethylene brassylate) (PEB) is a relatively unexplored polymer with many advantages. PEB is low in cost and made from castor oil, making it a sustainable resource. In this work, we have synthesized a new lignin-containing copolymer, lignin-graft-PEB. The biopolymer lignin was chemically modified by sebacic acid to introduce a carboxylic acid functionality. Lignin’s abundant hydroxyl groups were used for its modification. Another precursor of the copolymer, PEB, was prepared by ring-opening polymerization of ethylene brassylate in the presence of the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The condensation copolymerization of the modified lignin and PEB occurred by reactions between the TBD terminus of the PEB and the carboxylic acid of the modified lignin. A decent melting temperature (78 °C) of the new polymer enables thermal processing. The mechanical properties of the new lignin-graft-PEB can be conveniently controlled by changing the mass ratio of lignin and PEB and the molecular weight of PEB. The highest modulus of lignin-graft-PEB is 471.99 MPa, which is 3-fold higher than that of homoPEB.

Isolation of subpollen particles (SPPs) of birch: SPPs are potential carriers of ice nucleating macromolecules

Abstract. Within the last years pollen grains have gained increasing attention due to their cloud-forming potential. Especially the discovery that ice nucleating macromolecules (INMs) or subpollen particles (SPPs) obtained from pollen grains are able to initiate freezing has stirred up interest in pollen. INMs and SPPs are much smaller and potentially more numerous than pollen grains and could significantly affect cloud formation in the atmosphere. However, INMs and SPPs are not clearly distinguished. This has motivated the present study, which focuses on birch pollen and investigates the relationship between pollen grains, INMs, and SPPs. According to the usage of the term SPP in the medical fields, we define SPPs as the starch granules contained in pollen grains. We show that these insoluble SPPs are only obtained when fresh pollen grains are used to generate aqueous extracts from pollen. Due to the limited seasonal availability of fresh pollen grains, almost all studies have been conducted with commercial pollen grains. To enable the investigation of the SPPs we develop an alternative extraction method to generate large quantities of SPPs from commercial pollen grains. We show that INMs are not bonded to SPPs (i.e. can be washed off with water). Further, we find that purified SPPs are not ice nucleation active: after several times of washing SPPs with ultrapure water the ice nucleation activity completely disappears. To our knowledge, this is the first study to investigate the ice nucleation activity of isolated SPPs. To study the chemical nature of the INMs, we use fluorescence spectroscopy. Fluorescence excitation–emission maps indicate a strong signal in the protein range (maximum around λex = 280 nm and λem = 330 nm) with all ice nucleation active samples. In contrast, with purified SPPs the protein signal is lost. We also quantify the protein concentration with the Bradford assay. The protein concentration ranges from 77.4 µg mL−1 (highly concentrated INMs) to below 2.5 µg mL−1 (purified SPPs). Moreover, we investigate the connection between proteins and ice nucleation activity by treating the ice nucleation active samples with subtilisin A and urea to unfold and digest the proteins. After this treatment the ice nucleation activity clearly diminished. The results indicate a linkage between ice nucleation activity and protein concentration. The missing piece of the puzzle could be a glycoprotein which exhibits carboxylate functionalities, can bind water in tertiary structures, and displays degeneration and unfolding of its secondary structure due to heat treatment or reaction with enzymes. Even though purified SPPs are not ice nucleation active they could act as carriers of INMs and distribute those in the atmosphere.

New Carbazole-Based Organic Electrodes for Next Generation of Sustainable Lithium Batteries

Over the last decades, the widespread diffusion of energy storage systems, related to a global rethinking of the energy sources used for mobility, for industrial and household use, has been witnessed. In this framework, energy storage systems based on lithium-ion batteries will play a fundamental role in the transition towards green electricity production and use. However, the mass production of batteries based on inorganic materials, the reference materials for Li-ion technology, has shown various problems related to supply and recyclability: the abundance of these resources is very limited and characterized by an unfavorable geolocation, their extraction and processing costs are high and the materials are poorly recyclable1,2.To overcome these limitations, in recent decades scientists have focused on the study of organic-based materials: these compounds are capable of storing energy through redox reactions and are mainly composed of carbon, nitrogen, sulfur, oxygen and hydrogen atoms. Furthermore, they are characterized by low production costs and high recyclability, as well as the possibility of being obtained from natural sources, for an overall lower environmental impact3. Together with their high electrochemical performance, organic materials are excellent candidates to replace the inorganics-based electrodes.Organic materials can be categorized into two groups, based on the energy storage mechanism: the former uses a cation insertion (“n-type”), which involves an exchange of lithium ions with the electrolyte such as carbonyl-based molecule (as quinone compounds), organodisulfides, azocompounds and nitriles4, the latter is based on anion insertion in the redox process (p-type) such as aromatic amines (phenothiazine and phenoxazine), together with nitroxides (as TEMPO)5. In recent years, several studies on a new p-type functional group, based on carbazole moieties, have been reported in the literature6: it shows high average potentials (3.7 V vs. Li), one of the highest among organic molecules, and a good reversible capacity around 125 mAh g-1. The overall performances are comparable, both in terms of potential and capacity, to those obtained with conventional positive-electrode materials such as LiCoO2 or LiFePO4 7.Herein we would like to report on the design, the preparation and the electrochemical performance of a new set of carbazole-based molecules, cable of reversibly intercalating anions (p-type mechanism) with a high redox potential (4.0 V vs. Li+/Li0) as organic positive electrodes for energy storage applications.Two new N-substituted carbazole molecules, lithium carbazole acetate (LiCZA) and lithium carbazole benzoate (Li-4-BACZ), were synthesized with a carboxyl functionality, in order to avoid the dissolution of the active material in the liquid electrolyte solvent. Both molecules showed an improvement in cycling stability, and in the case of Li-4-BACZ, an increase in the redox potential of 100 mV was also observed. Moreover, several different types of electrolytes were tested in order to evaluate the impact of the anion type on the p-type insertion mechanism8. Two different electrolytes were tested, LiPF6 and LiClO4, dissolved both in a 1:1 EC/DMC mixtures and in propylene carbonate. Keywords: Carbazole, lithium batteries, organic electrode, organic batteries. References Scrosati, B.; Garche, J. J. Power Sources 2010, 195, 2419−2430.Poizot, P.; Dolhem, F. Energy Environ. Sci. 2011, 4, 2003−2019.Poizot P., Gaubicher J., Renault S., Dubois L., Liang Y., Yao Y., Chem. Rev.2020, 120, 14, 6490–6557Bhosale M. E., Chae S., Kim J. M., Choi J.-Y., J. Mater. Chem. A, 2018, 6, 19885–19911Esser B., Dolhem F., Becuwe M., Poizot P., Vlad A., Brandell D., J. of Power Sources 2021, 482, 228814Yao M., Senoh H., Skai T., Kiyobayashi T., J. of Power Sources 2012, 202, 364-368Goodenough J. B., Park K.-S., J. Am. Soc. 2013, 135, 1167−1176Murugesan R., Dolhem F., Davoisne C., Becuwe M., ChemSusChem 2020, 13, 2364 – 2370

In search for novel liver X receptors modulators by extending the structure–activity relationships of cholenamide derivatives

N,N-Dimethyl 3β-hydroxychol-5-en-24-amide (DMHCA, 3) is the prototype of cholenamides, a class of steroidal LXR modulators characterized by the nucleus of Δ5-cholen-3β-ol and the presence of an amide moiety at C-24. DMHCA (3) has been reported to act as a gene-selective modulator able to fully induce ABCA1 expression whilst poorly up-regulate the expression of FASN and SREBP-1α genes. With the aim to widen the limited structure-activity relationships of DMHCA (3), herein we describe the synthesis and the biological evaluation of nine novel derivatives, resulting from a) the homologation of DMHCA’s side-chain to give N,N-dimethyl 3β-hydroxy-24a-homochol-5-en-24a-amide (4); b) the distal branching of the side-chain of 3 and 4 by introducing an ethyl group at C-23 and C-24, respectively; c) the replacement of the dimethyl amide moiety of all the derivatives with a carboxylic acid function. While broadening the structure-activity relationships of the class of cholenamides, we were successful in the discovery of (24R)-N,N-dimethyl-24-ethyl-3β-hydroxy-24a-homochol-5-en-24a-amide (6) as a novel LXR agonist with improved profile in term of selective gene modulation respect to the prototype DMHCA (3); indeed, 6 was able to up-regulate the expression of ABCA1 more than DMHCA (3), without to induce SREBP-1c, differently from DMHCA (3). Moreover, 6 induced the expression of FASN less than 3 and interestingly was a negative modulator towards SCD1 in contrast to DMHCA (3), which instead weakly induced the expression of this gene.

Functionalization using biocompatible carboxylated cyclodextrins of iron-based nanoMIL-100

Here we report the first example of nanoMIL-100 particles modified with monomeric cyclodextrin derivatives of different length by exploiting strong interactions between non-saturated iron trimers at the external surface and carboxylate functionalities located at the end of biocompatible and flexible linkers of cyclodextrins. The main results revealed that, after the functionalization, the cyclodextrins are selectively located at the external surfaces covering the nanoparticles. Z potential measurements show that this functionalization induced changes respect to the bare nanoMIL-100 particles, however, the presence of the cyclodextrins does not modify the size neither porosity of the nanoparticles. The amount of cyclodextrins attached, investigated by thermogravimetry, increases with the length of the linker between CD cavity and nanoparticle surface, reaching up a 9 % wt. Auger spectroscopy suggested a clear predominant sp3 character after the functionalizations (vs. sp2 predominance in the unmodified nanoMIL-100). This study supposes the creation of an alternative family of hybrids based on carboxylated monomeric cyclodextrins.

Density functional theory investigation of the electronic and optical properties of metallo-phthalocyanine derivatives

The electronic and optical properties of metallo-phthalocyanine derivatives have been calculated by using density functional theory. Starting from a reference Zn(II) phthalocyanine the structure has been varied by changing the nature of the transition metal, by adding carboxylic functions, as well as by considering the extension of the aromatic rings with fused phenyl moieties, with the perspective of optimizing their performance as sensitizers in solar cells. Calculations demonstrate that the transition metal (Ni, Mn, Fe, Co, and Cu versus Zn) has a small impact on the free energies of the primary processes (injection, recombination, and regeneration), that adding several carboxylic acid functions has a cooperative role to optimize the injection process, and that the addition of fused phenyl rings increases the light harvesting efficiency and the free energy of injection. Highlights • DFT is efficient for designing metallo-phthalocyanines with optimized substituents • The transition metal has a small impact on the free energies of the primary processes • carboxylic acid functions have a cooperative role to optimize the injection process • Fused phenyl rings increase the light harvesting efficiency and the free energy of injection

‘‘Biopolymer-PAA and surfactant-CTAB assistant solvothermal synthesis of Zn-based MOFs: design, characterization for removal of toxic dyes, copper and their biological activities”

Zn-BTC(1) and its polymeric composites Zn-BTC@PAA(2) and Zn-BTC@PAA@CTAB)(3) MOFs are synthesized using Zinc acetate; BTC (Benzene tri-carboxylic acid); PAA (Polyacrylic acid); and CTAB (Cetyl trimethyl ammonium bromide)by in situ solvothermal method. FT-IR spectra of 1 reflected in 2, and 3 suggesting the presence of Zn-BTC in polymer composites. PXRD patterns of 1–3 MOFs are analogous, indicating that the Zn-BTC phase is consistent in polymer composites. While SEM-EDX studies confirm the morphology, elemental composition and presence of Zn in all MOFs. Thermal analysis of 1–3 shows polymer composites are more thermal stable than 1. MOF 3 composite shows potential dye adsorption towards cationic (MB) and anionic dyes (MO, CR) compared to 1 and 2. It also removes copper metal ions up to 95% within 120 mins, following second order kinetic absorption studies favours chemical adsorption. All zinc polymeric composite MOFs exhibit good antibacterial activity against Bacillus subtilis, E.coli, and antifungal activity against Saccharomyces cerevisiae due additional carboxylate and cationic function groups in composites.

Synthesis of Tailored Perfluoro Unsaturated Monomers for Potential Applications in Proton Exchange Membrane Preparation.

The aim of the present work is the synthesis and characterization of new perfluorinated monomers bearing, similarly to Nafion®, acidic groups for proton transport for potential and future applications in proton exchange membrane (PEM) fuel cells. To this end, we focused our attention on the synthesis of various molecules with (i) sufficient volatility to be used in vacuum polymerization techniques (e.g., PECVD)), (ii) sulfonic, phosphonic, or carboxylic acid functionalities for proton transport capacity of the resulting membrane, (iii) both aliphatic and aromatic perfluorinated tags to diversify the membrane polarity with respect to Nafion®, and (iv) a double bond to facilitate the polymerization under vacuum giving a preferential way for the chain growth of the polymer. A retrosynthetic approach persuaded us to attempt three main synthetic strategies: (a) organometallic Heck-type cross-coupling, (b) nucleophilic displacement, and (c) Wittig–Horner reaction (carbanion approach). Preliminary results on the plasma deposition of a polymeric film are also presented. The variation of plasma conditions allowed us to point out that the film prepared in the mildest settings (20 W) shows the maximum monomer retention in its structure. In this condition, plasma polymerization likely occurs mainly by rupture of the π bond in the monomer molecule.

Sensitive detection of E. coli using bioconjugated fluorescent silica nanoparticles

Fluorescent dye-doped silica nanoparticles have been a major focus of research and development as potential fluorescent probes in biological systems. This is due to their strong fluorescence intensity, excellent photostability, biocompatibility, and ease of surface modification for bioconjugation. In this study, spherical silica nanoparticles doped with fluorescein isothiocyanate (FITC) were synthesized using reverse microemulsion method. The average diameter of the nanoparticles was 78 nm with a narrow size distribution (78 ± 49.50 nm). FITC was incorporated into the silica sphere through 3-aminopropyltriethoxysilane, which minimized the leakage of the dye. Only about 30% of the dye leaked out from these nanoparticles, after they were sonicated in aqueous medium for 60 min and the fluorescent intensity remained comparatively constant over time, showing an increased photostability (∼ 1.5 times higher) compared to the free dye in solution. The fluorescence emission spectrum of nanoparticles showed no apparent shift (maximum emission at 518 nm) when compared with the free dye in solution. The nanoparticle surface was chemically modified with amine and carboxyl functionalities to allow for Escherichia coli antibody conjugation. E. coli bacteria is widely used as a biological indicator to identify fecal contamination in food and water samples. Nanoparticle-based biosensors for the detection of E. coli have a vital importance in water quality, public health, and food safety. The E. coli in water was successfully observed under a fluorescence microscope using the antibody conjugated fluorescent silica nanoparticles synthesized, proving the feasibility of using them in a biosensor for qualitative determination of E. coli. The significance of this study lies in the relatively simple synthetic procedures as compared to those that have been in other studies reported in the literature. The ability to detect live cells under the fluorescence microscope further proves the suitability of these functionalized nanoparticles in live cell imaging.

Efficient and Recyclable Heterogeneous Catalyst Based on PdNPs Stabilized on a Green-Synthesized Graphene-like Nanomaterial: Effect of Surface Functionalization.

This work reports for the first time a straightforward and efficient approach to covalent surface functionalization of a sustainable graphene-like nanomaterial with abundant carboxylic acid groups. This approach results in an efficient and robust chelatant platform for anchoring highly dispersed ultrasmall palladium particles with excellent catalytic activity in the reduction of both cationic (methylene blue, MB) and anionic (eosin-Y, Eo-Y) toxic organic dyes. The large-specific-surface-area (SBET = 266.94 m2/g) graphene-like nanomaterial (GHN) was prepared through a green and cost-effective pyrolysis process from saccharose using layered bentonite clay as a template. To introduce a high density of carboxylic acid functions, GHN was first doubly functionalized by successive grafting reaction using two different strategies: (i) in the first case, GHN was first grafted by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and then bifunctionalized by chemical grafting of tris(4-hydroxyphenyl)methane triglycidyl ether (TGE). In the second case, the grafting order of the two molecules has been reversed. GHN-GPTMS-TGE provided the highest number of grafted reactive epoxy groups, and it was selected for further functionalization with carboxylic acid functions via a ring-opening reaction through a two-step hydrolysis (H2SO4)/oxidation (KMnO4) approach. The GHN nanomaterial bearing carboxylic acid groups was then treated with sodium hydroxide to produce a deprotonated carboxylic acid-rich platform. Finally, due to a high density of accessible chelatant carboxylic acid groups, GHN-COO- binds strongly a great amount of Pd2+ ions to form stable complexes which after reduction by NaBH4 leads to highly dispersed, densely anchored, and uniformly distributed nanoscale Pd particles (d ∼ 4.5 nm) on the surface of the functionalized GHN. The GHN-COO-@PdNPs nanohybrid proved to be highly efficient for dye reduction by NaBH4 in aqueous solution at room temperature. Moreover, because of the high stability of the as-prepared graphene-like supported PdNPs, it exhibited very good reusability and could be recycled up to eight times without any significant loss in activity.

Size- and Shape-Selective Catalysis with a Functionalized Self-Assembled Cage Host.

A self-assembled Fe4L6 cage with internally oriented carboxylic acid functions was shown to catalyze a variety of dissociative nucleophilic substitution reactions that proceed via oxocarbenium ion or carbocation intermediates. The catalytic behavior of the cage was compared to that of other small acid catalysts, which illustrated large differences in reactivity of the cage-catalyzed reactions, dependent on the structure of the substrate. For example, only a 5% cage confers a 1000-fold rate acceleration of the thioetherification of vinyldiphenylmethanol when compared to the rate with free carboxylic acid surrogates but only a 52-fold acceleration in the formation of small thioacetals. Multiple factors control the variable reactivity in the host, including substrate inhibition, binding affinity, and accessibility of reactive groups once bound. Simple effective concentration increases or the overall charge of the cage does not explain the variations in reactivity shown by highly similar reactants in the host: small differences in structure can have large effects on reactivity. Reaction of large spherical guests is highly dependent on substitution, whereas flat guests are almost unaffected by size and shape differences. The cage is a promiscuous catalyst but has strong selectivity for particular substrate shapes, reminiscent of enzymatic activity.

Replacement of Volatile Acetic Acid by Solid SiO2@COOH Silica (Nano)Beads for (Ep)Oxidation Using Mn and Fe Complexes Containing BPMEN Ligand.

Mn and Fe BPMEN complexes showed excellent reactivity in catalytic oxidation with an excess of co-reagent (CH3COOH). In the straight line of a cleaner catalytic system, volatile acetic acid was replaced by SiO2 (nano)particles with two different sizes to which pending carboxylic functions were added (SiO2@COOH). The SiO2@COOH beads were obtained by the functionalization of SiO2 with pending nitrile functions (SiO2@CN) followed by CN hydrolysis. All complexes and silica beads were characterized by NMR, infrared, DLS, TEM, X-ray diffraction. The replacement of CH3COOH by SiO2@COOH (100 times less on molar ratio) has been evaluated for (ep)oxidation on several substrates (cyclooctene, cyclohexene, cyclohexanol) and discussed in terms of activity and green metrics.

Metal‐Free Doubly Decarboxylative Three‐Component Reaction: Synthesis of Propargyl Amines

AbstractArylalkynoic acids, glyoxylic acid, and amines were reacted in the absence of transition metal catalysts to produce the corresponding arylpropargyl amines via double decarboxylation. In addition to cyclic secondary amines, non‐cyclic secondary amines also reacted with various substituted arylalkynoic acids and glyoxylic acid to afford the desired products in good yields. It was revealed that the carboxylic acid functionality was important for increasing the product yield.