Presence Of Tetrabutylammonium Bromide Research Articles

Polymorphism and Its Influence on Catalytic Activities of Lanthanide-Glutamate-Oxalate Coordination Polymers.

To study the relationship between polymorphism and catalytic activities of lanthanide coordination polymers in the cycloaddition reactions of CO2 with epoxides, the monoclinic and triclinic polymorphs of [LnIII(NH3-Glu)(ox)]·2H2O, where LnIII = LaIII (I), PrIII (II), NdIII (III), SmIII (IV), EuIII (V), GdIII (VI), TbIII (VII), and DyIII (VIII), NH3-Glu- = NH3+ containing glutamate, and ox2- = oxalate, were synthesized and characterized. Factors determining polymorphic preference, the discrepancy between the two polymorphic framework structures, potential acidic and basic sites, thermal and chemical stabilities, active surface areas, void volumes, CO2 sorption/desorption isotherms, and temperature-programmed desorption of NH3 and CO2 are comparatively presented. Based on the cycloaddition of CO2 with epichlorohydrin in the presence of tetrabutylammonium bromide under solvent-free conditions and ambient pressure, catalytic activities of the two polymorphs were evaluated, and the relationship between polymorphism and catalytic performances has been established. Better performances of the monoclinic catalysts have been revealed and rationalized. In addition, the scope of monosubstituted epoxides was experimented and the outstanding performance of the monoclinic catalyst in the cycloaddition reaction of CO2 with allyl glycidyl ether under ambient pressure has been disclosed.

Halogen-Decorated Metal-Organic Frameworks for Efficient and Selective CO2 Capture, Separation, and Chemical Fixation with Epoxides under Mild Conditions.

In the present work, three novel halogen-appended cadmium(II) metal-organic frameworks [Cd2(L1)2(4,4'-Bipy)2]n·4n(DMF) (1), [Cd2(L2)2(4,4'-Bipy)2]n·3n(DMF) (2), and [Cd(L3)(4,4'-Bipy)]n·2n(DMF) (3) [where L1 = 5-{(4-bromobenzyl)amino}isophthalate; L2 = 5-{(4-chlorobenzyl)amino}isophthalate; L3 = 5-{(4-fluorobenzyl)amino}isophthalate; 4,4'-Bipy = 4,4'-bipyridine; and DMF = N,N'-dimethylformamide] have been synthesized under solvothermal conditions and characterized by various analytical techniques. The single-crystal X-ray diffraction analysis demonstrated that all the MOFs feature a similar type of three-dimensional structure having a binuclear [Cd2(COO)4(N)4] secondary building block unit. Moreover, MOFs 1 and 2 contain one-dimensional channels along the b-axis, whereas MOF 3 possesses a 1D channel along the a-axis. In these MOFs, the pores are decorated with multifunctional groups, i.e., halogen and amine. The gas adsorption analysis of these MOFs demonstrate that they display high uptake of CO2 (up to 5.34 mmol/g) over N2 and CH4. The isosteric heat of adsorption (Qst) value for CO2 at zero loadings is in the range of 18-26 kJ mol-1. In order to understand the mechanism behind the better adsorption of CO2 by our MOFs, we have also performed configurational bias Monte Carlo simulation studies, which confirm that the interaction between our MOFs and CO2 is stronger compared to those with N2 and CH4. Various noncovalent interactions, e.g., halogen (X)···O, Cd···O, and O···O, between CO2 and the halogen atom, the Cd(II) metal center, and the carboxylate group from the MOFs are observed, respectively, which may be a reason for the higher carbon dioxide adsorption. Ideal adsorbed solution theory (IAST) calculations of MOF 1 demonstrate that the obtained selectivity values for CO2/CH4 (50:50) and CO2/N2 (15:85) are ca. 28 and 193 at 273 K, respectively. However, upon increasing the temperature to 298 K, the selectivity value (S = 34) decreases significantly for the CO2/N2 mixture. We have also calculated the breakthrough analysis curves for all the MOFs using mixtures of CO2/CH4 (50:50) and CO2/N2 (50:50 and 15:85) at different entering gas velocities and observed larger retention times for CO2 in comparison with other gases, which also signifies the stronger interaction between our MOFs and CO2. Moreover, due to the presence of Lewis acidic metal centers, these MOFs act as heterogeneous catalysts for the CO2 fixation reactions with different epoxides in the presence of tetrabutyl ammonium bromide (TBAB), for conversion into industrially valuable cyclic carbonates. These MOFs exhibit a high conversion (96-99%) of epichlorohydrin (ECH) to the corresponding cyclic carbonate 4-(chloromethyl)-1,3-dioxolan-2-one after 12 h of reaction time at 1 bar of CO2 pressure, at 65 °C. The MOFs can be reused up to four cycles without compromising their structural integrity as well as without losing their activity significantly.

Cyclic carbonate synthesis from CO2 and epoxides catalyzed by lanthanide derivatives comprising arylhydrazones of β-diketones

Two known lanthanide complexes, [KLa(HL1)2{(CH3)2NCHO}2(H2O)3] (1) and [Sm(H2O)9](E-H2L2)3·2H2O (2), (KH2L1 = potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate, KH2L2 = potassium (E,Z)-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate), have been prepared and tested as catalysts in the cycloaddition of CO2 with epoxides in the presence and absence of co-catalysts (tetrabutylammonium chloride (TBACl), tetrabutylammonium bromide (TBABr) and tetrabutylammonium iodide (TBAI)). Complex 1 was found to be the most efficient catalyst in the presence of TBABr, with conversions up to 97 %, at 40 °C, of the epoxides to the corresponding cyclic carbonates. The catalytic activity of 1 is dependent on the nature of the substrate, ranging from 23 to 97 %.

Halogen Bonding in the Decoration of Secondary Coordination Sphere of Zinc(II) and Cadmium(II) Complexes: Catalytic Application in Cycloaddition Reaction of CO2 with Epoxides.

Three new zinc(II) complexes [Zn(H2L3)2(H2O)3] (Zn2), [Zn(H3L2a)(H2O)3]n (Zn3) (H3L2a = 2,4-diiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazineyl)isophthalate) and [Zn(HL4)(DMF)(H2O)]n (Zn4) were synthesized by the reaction of Zn(II) salts with 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl) isophthalic acid (H3L3), 2,4,6-triiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazineyl) isophthalic acid (H5L2) (in the presence of NH2OH·HCl) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)-2,4,6-triiodoisophthalic acid (H3L4), respectively. According to the X-ray structural analysis, the intramolecular resonance-assisted hydrogen bond ring remains intact, with N···O distances of 2.562(5) and 2.573(5) Å in Zn2, 2.603(6) Å in Zn3, and 2.563(8) Å in Zn4. In the crystal packing of Zn3, the cooperation of I···O and I···I types of halogen bonds between tectons leads to a one-dimensional supramolecular polymer, while I···O interactions aggregate 1D chains of coordination polymer Zn4. These new complexes (Zn2, Zn3, and Zn4) and known [Zn(H3L1)(H2O)2]n (Zn1) (H3L1 = 5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene) hydrazineyl)isophthalate), {[Zn(H3L1)(H2O)3]·3H2O}n (Zn5), [Cd(H3L1)(H2O)2]n (Cd1), {[Cd(HL3)(H2O)2(DMF)]·H2O}n (Cd2), [Cd(H3L3)]n (Cd-3), {[Cd2(μ-H2O)2(μ-H2L4)2(H2L4)2]·2H2O}n (Cd4), and {[Cd(H3L1)(H2O)3]·4H2O}n (Cd5) were tested as catalysts in the cycloaddition reaction of CO2 with epoxides in the presence of tetrabutylammonium halides as the cocatalyst. The halogen-bonded catalyst Zn4 is the most efficient one in the presence of tetrabutylammonium bromide by affording a high yield (85-99%) of cyclic carbonates under solvent-free conditions after 48 h at 40 bar and 80 °C.

Title: Cr(III) Incorporated Melamine‐Terephthalaldehyde Porous Organic Framework Nanosheet Catalyst for Carbon Dioxide Fixation Reaction

AbstractCr(III) centers have been incorporated into melamine‐terephthalaldehyde porous organic framework (MT‐POF) through N‐donor site coordination. Morphological studies by SEM give evidence of the transformation of spherulitic texture of non‐metalated MT‐POF to aggregated platelike structure in chromium metalated POF, MT‐Cr(III) POF (bulk). The flattening in the surface morphology of bulk MT‐Cr(III) POF might be a consequence of conformational change in POF caused by the template effect of the Cr(III) coordination. On sonication, bulk MT‐Cr(III) POF transformed into a distinguishable stacked nanosheet structure in MT‐Cr(III) POFN as revealed by FE‐SEM and TEM images. MT‐Cr(III) POFN could catalyse the carbon dioxide cycloaddition reaction to epoxides to yield cyclic carbonates in presence of tetrabutylammonium bromide (TBAB) co‐catalyst. It was found that bulkier epoxide substrates showed lesser conversions to their corresponding cyclic carbonates (styrene oxide, 41 %; allyl glycidyl ether, 70 %; butyl glycidyl ether, 63 % conv.), whereas smaller substrates showed much higher conversions (epichlorohydrin, 96 %; epibromohydrin, 95 % conv.) under the reaction conditions [MT‐Cr(III) POFN, 10 mg; TBAB, 2 mol%; 5 bar CO2; 60 °C] giving a clear evidence of the substrate discrimination. The reason for the lesser conversions of the bigger substrates can be attributed to the steric clash rendered by the POF network.

Adenine‐Functionalized Dendritic Fibrous Nanosilica as Bifunctional Catalyst for CO2 Fixation into Cyclic Carbonate

AbstractCycloaddition of CO2 with epoxide to form cyclic carbonate is one of the most promising approaches to mitigate the rising level of CO2 in the atmosphere. Therefore, the design and synthesis of new materials which can efficiently catalyze such reactions has become an important research area. This article reports on the synthesis of a new material, adenine functionalized dendritic fibrous nanosilica (DAD), by functionalizing the surface of dendritic fibrous nanosilica (DFNS) with an N‐containing heterocyclic nucleobase adenine using a bifunctional isocyanate crosslinker ((EtO)3Si(CH2)3NCO). The surface amine functionalities enable DAD to show selective CO2 adsorption (0.44 mmol/g, at 1 bar CO2 pressure and 298 K temperature) due to acid‐base interaction between CO2 and amine groups. Moreover, DAD efficiently catalyzes the fixation of CO2 with a variety of epoxides into corresponding cyclic carbonates in the presence of TBAB (tetrabutylammonium bromide) co‐catalyst under solvent‐free conditions. The DFNS skeleton of DAD offers a high surface area for enhanced CO2 adsorption, while its organic surface groups, adenine and carbamide, boost the selectivity and activate the epoxide ring and CO2 for cycloaddition reaction. The strong covalent linkage of surface groups in DAD renders robust structural integrity, enabling the catalyst to be recycled multiple times with negligible reduction in its catalytic performance.

Novel Antireflection Coatings Obtained by Low-Temperature Annealing in the Presence of Tetrabutylammonium Bromide and Gold Nanoparticles.

In this work, nanoporous antireflective coatings on silicate glass were obtained from silicon dioxide sol compositions by the sol-gel method in the presence of quaternary ammonium salt (tetrabutylammonium bromide) at different annealing temperatures (200-250 °C). Varying the salt concentration from 3 to 5 wt.%, we achieved the transmittance of the coatings of about 97% at 250 °C in comparison with 91% for clean glass in the wavelength range from 400 to 1100 nm. The addition of gold nanoparticles to the composition containing 5 wt.% tetrabutylammonium bromide allowed us to decrease the annealing temperature to 200 °C, preserving the transmittance at the level of 96.5%. For this case, the optimal concentration of gold nanoparticles is determined (2.6 × 10-9 mol/mL). According to the SEM analysis, the obtained antireflective coatings contain pores with a minimum area size up to 4 nm2.

Determination of Naphthol Yellow S and Chromotrope 2B at trace levels by spectrophotometry after mixed micellar cloud point extraction using TX-114 and TBAB

A method for the determination of two anionic dyes, Naphthol Yellow S (NYS) and Chromotrope 2B (CTB) in the presence of TBAB (Tetra butyl ammonium bromide) and Triton X-114 (Polyethylene glycol tert-octylphenyl ether) mixed micelles was developed by cloud point extraction pre-concentration technique. Good extraction efficiency was achieved for both NYS and CTB(85-92)% from their aqueous solutions by the optimization of pH of the solution, concentration of surfactants and salting out agent. Linearity was found to be in the range 1.5 – 30.0 μg mL-1for NYS and 1.86 – 27.2 μg mL-1 for CTB. The limit of detection was found to be in ngmL-1 range. Langmuir adsorption model was successfully applied to the phase separation process. The enthalpy, entropy and free energy change for solubilization of these dyes in surfactant phase were also determined. This method was then used to determine the dye concentration in the tap and sea water samples.

Methyl 5-Imino-2-methyl-1,10a-dihydro-5H-chromeno[2,3-b]pyridine-3-carboxylate

Multicomponent reactions are valuable synthetic tools to deliver highly functionalized motifs starting from simple building blocks in only one step and in an atom-economical way. Herein we disclose the structure of a new and unexpected compound, the methyl 5-imino-2-methyl-1,10a-dihydro-5H-chromeno[2,3-b]pyridine-3-carboxylate, which was formed in the ohmic-heating-assisted multicomponent Hantzsch reaction of 3-formylchromone with methyl acetoacetate and ammonium acetate, in aqueous medium, in the presence of tetrabutylammonium bromide as phase transfer catalyst. The title compound was isolated with no need of chromatographic separation and was analyzed by nuclear magnetic resonance (1H and 13C-NMR, HSQC and HMBC) spectroscopy, mass spectrometry (MS) and high-resolution mass spectrometry (HRMS). Its formation as the main reaction product was observed when the reaction was performed using ohmic heating, which may lead to some speculations about the possible existence of specific effects of ohmic heating in the reactivity pathway because of the passage of an alternating electric current of high frequency within the reaction media, opening new opportunities for further investigations of the potential of this thermal processing method in organic synthesis and reactivity optimization.

Molecular diversity of the base-promoted reaction of phenacylmalononitriles with dialkyl but-2-ynedioates.

In the presence of tetrabutylammonium bromide (TBAB), the cycloaddition reaction of phenacylmalononitriles with dialkyl but-2-ynedioates in acetonitrile at room temperature resulted in 3,3-dicyano-5-hydroxy-5-arylcyclopent-1-ene-1,2-dicarboxylates in high yields. More importantly, the DABCO-promoted domino reaction of two molecules of each phenacylmalononitrile and dialkyl but-2-ynedioate in acetonitrile at room temperature afforded unique multifunctionalized carboxamide-bridged dicyclopentenes in moderate to good yields and with high diastereoselectivity.

Sodium sulfide-based polysulfide polymers: synthesis, cure, thermal and mechanical properties

In this study, a series of polysulfide polymers were synthesized using aqueous monomer (sodium sulfide) and organic monomers (methylene dichloride, ethylene dichloride, 1,4-dichlorobutane, and α,α′-dichloro-p-xylene) via interfacial polymerization. Next, thepolymers, sulfur, zinc oxide (ZnO), stearic acid, and N-cyclohexyl-2-benzothiazole sulfenamide (CBS), were compounded using a two-roll mill and cured by a rheometer. The as-synthesized and cured samples are characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Shore A, and tensile tests. Also, the molecular weight of the as-synthesized samples was determined by proton nuclear magnetic resonance (1H NMR). The results showed that in the as-synthesized linear polymers, with increasing the number of carbon in the structure, crystallinity, hardness, glass transition temperature (Tg ), and melting point (Tm ) decrease. Also, the investigation of thermal degradation showed that poly(p-xylene sulfide) and poly(butylene sulfide) have the lowest and highest thermal resistance, respectively. The results of polymerization yield showed that without the presence of tetrabutylammonium bromide (TBAB), which is used as a phase transfer catalysts (PTC), the polymerization reaction of poly(butylene sulfide) and poly(p-xylene sulfide) is inefficient. The samples have a completely amorphous structure after the curing process. Moreover, the Tg , thermal resistance, and hardness increased.

Environmentally benign melamine functionalized silica-coated iron oxide for selective CO2 capture and fixation into cyclic carbonate

The development of new materials capable of fixing CO2 into value-added products has become an exciting research field. Besides mitigating the rising level of CO2, such materials also enable CO2 as a C1 carbon source for useful industrial synthons. This article reports on the stepwise synthesis of a melamine functionalized silica-coated iron oxide (FSNM) material for selective CO2 capture and its catalytic conversion into a useful product. The synthesis of FSNM has been achieved by covalently grafting the melamine group in the pores of mesoporous silica-coated Fe3O4 (Fe3O4@SiO2) particle using isocyanate as a cross-linker. While the Fe3O4 core, owing to its superparamagnetic property, enables the easy retrieval of the material from the reaction mixture and, thus, enhances the recyclability, mesoporous silica coating offers a larger surface area for adsorption. The organic functionalities, containing melamine and carbamide moieties, facilitate the selective adsorption of CO2 on the material with a maximum CO2 uptake of 0.48 mmol/g at 1 bar and 298 K with excellent CO2/N2 selectivity. Moreover, the acid-base interactions between the acidic CO2 and basic amine groups enable the FSNM to catalyze the cycloaddition of CO2 with different epoxides to afford a series of cyclic carbonates, in the presence of tetrabutylammonium bromide (TBAB) as a co-catalyst, under facile and solvent-free conditions. These results strongly support that melamine functionalized Fe3O4@SiO2 affords new aspects towards environmentally friendly and recoverable hybrid adsorbent for adsorption and fixation of CO2 into the valuable products.

Cyclic carbonates of rapeseed methyl esters as monomers for urethane composites

The two-stage synthesis of cyclic carbonates based on methyl esters of fatty acids from rapeseed oil is characterized. The first stage involves the synthesis of epoxides by the reaction of unsaturated methyl esters of rapeseed fatty acids with hydrogen peroxide, orthophosphoric and acetic acids. The second step is a carbonization reaction, which was carried out by passing carbon dioxide through the reactive mixture in the presence of tetrabutylammonium bromide as a catalyst. A reactive oligourethane based on cyclocarbonates cyclic carbonates of rapeseed fatty acids and piperazine was synthesized by the non-isocyanate method via the interaction of cyclocarbonate group with the amino group of piperazine. Polymer composites based on synthesized cyclocarbonates, epoxides and amines of different chemical nature were prepared and studied. Thus, there is a possibility of regulating the physical and mechanical properties of epoxyurethane composites.

Effect of electrolytes on the interfacial rheological behaviors of N-cocoyl glycinate

Amino acid surfactants have been applied to numerous areas of science and are often used in the presence of electrolytes. In this study, the interfacial rheological behaviors of potassium N-cocoyl glycinate (KCGl), an amino acid surfactant, with three kinds of electrolytes (KCl, CaCl2 and tetrabutylammonium bromide (TBABr)) have been investigated using the oscillating drop method. The interfacial tensions (IFTs) and dilational rheological parameters show that KCGl in conjunction with electrolytes has enhanced interfacial activity and stronger intermolecular interaction than pure KCGl, indicating that electrolytes contribute to denser molecular packing at the oil–aqueous interface. Interestingly, the butyl groups of TBA+ hinder closer arrangement of molecules at the interface, hindering KCGl ability to form a tightly packed layer compared with K+ and Ca2+ electrolytes. The relaxation processes, such as diffusion exchange of surfactant molecules between the aqueous phase and interface, are more probable to occur. Therefore, more viscoelastic films are formed in the presence of TBABr.

Eco-Friendly Approach for the Synthesis of Thiophene Linked Benzothiazepines as Biocompatible Free Radical Scavengers

A series of new thiophene tethered benzothiazepines (5a-h) were synthesized through citrus juice mediated (4+3) annulations of thienyl chalcones with 2-aminobenzenethiol in the presence of tetrabutylammonium bromide as phase transfer catalyst under reflux conditions. The synthesized compounds were characterized by spectroscopic and CHN analysis. To check the antioxidant potentials of the synthesized compounds, in vitro DPPH and hydroxyl radical scavenging assays were conducted. The results shows that amongst the series, compounds 5b with (21.44-49.72%) and (16.88-42.60%); 5c with (24.88-56.00%) and (22.33-53.12%); and 5h with (22.80-47.10%) and (15.33-44.12%) excellent DPPH and hydroxyl radical potencies comparable with the respective standards used in the experiments.

Investigation of surface adsorption and thermodynamic properties of 1-tetradecyl-3-methylimidazolium bromide in the absence and presence of tetrabutylammonium bromide in aqueous medium

The aggregation behavior of imidazolium-based long-chain ionic liquid 1-tetradecyl-3-methylimidazolium bromide [C14mim][Br] has been investigated in the absence and presence of (1, 2, and 5) mM tetrabutylammonium bromide (C4H9)4NBr at three temperatures (298.15, 308.15, and 318.15) K. The critical micelle concentration (CMC), surface parameters such as maximum surface excess concentration (), the minimum area surfactant monomer at the air/water interface (), surface tension at CMC () and surface pressure () are determined by employing conductivity and surface tension measurements. Various thermodynamic parameters of micellization such as standard free energy of micellization (), standard enthalpy of micellization (), and standard entropy of micellization () are calculated by utilizing the temperature dependence of CMC observed using conductivity study. Other thermodynamic parameters such as free energy of adsorption (Δ) and surface free energy () are also evaluated. Refractive index measurements and UV–vis spectroscopic studies have been utilized to confirm the values of CMC obtained via conductivity and surface tension measurements. FTIR spectroscopic studies signify the various interactions prevailing in the system constituting long-chain ionic liquid and electrolyte.

Nanoporous N-doped Carbon/ZnO hybrid derived from zinc aspartate: An acid-base bifunctional catalyst for efficient fixation of carbon dioxide into cyclic carbonates

A nanoporous N-doped carbon/ZnO hybrid material (Zn-Asp-300) is facilely prepared by direct thermolysis of zinc aspartate precursor, which could be used as effective catalyst for the cycloaddition reaction of CO2 and epoxides in the presence of tetrabutylammonium bromide (TBAB) as co-catalyst. At temperature 80 °C and CO2 pressure 1.0 MPa, Zn-Asp-300 demonstrates good catalytic activity for various epoxides as substrates, gives up to 96.7% of yield and ca. 100% of selectivity. A variety of characterizations indicate that the resultant Zn-Asp-300 has abundant zinc oxide, as well as pyridinic and pyrrolic N atoms, which act as Lewis acid and basic sites that enable the activation of CO2 and epoxide, respectively, thus facilitating the cycloaddition reaction. Notably, the cycloaddition reaction also can be completed (92.2% of yield) on Zn-Asp-300 while only using simulated solar light as energy source. Moreover, Zn-Asp-300 also shows good chemical stability and reusability during the cycloaddition reaction. The potential application of Zn-Asp-300 in both thermal and photothermal catalysis of cycloaddition reaction is a promising and sustainable approach towards reducing CO2 emission and the utilization of CO2.

Environmentally benign synthesis of substituted pyrazoles as potent antioxidant agents, characterization and docking studies

Oxidative stress is an important cause of neurogenerative diseases; treatment with a reliable antioxidant with no side effects is a potential tool to overcome with such diseases. The aim of this study is to explore new and effective antioxidants and their mechanism; in this context, the manuscript demonstrates the greener approach for the synthesis of series of novel thiophene-pyrazole hybrids, 5(a–m) through [3 + 2] annulation of chalcones, 3(a–g) and phenylhydrazine hydrochloride, 4(a–b) in citrus extract medium in the presence of tetrabutylammonium bromide. The structures were confirmed by spectroscopic and crystallographic studies and further screened in vitro for their free radical scavenging activities. Preliminary assessment results show that, among the synthesized series, compounds 5c, 5d, 5f, 5i, 5j, 5l, and 5m have potent antioxidant activities. Docking studies reveal that the ligands 5e, 5f, 5m, and 5q bind to superoxide dismutase at the Cu–Zn domain and thereby increase its activity and reduce reactive oxygen species; therefore, these ligands might be better antioxidant molecules which could down and regulate the oxidation stress within the body.

Porous aluminum-based DUT metal-organic frameworks for the transformation of CO2 into cyclic carbonates: A computationally supported study

Abstract Two aluminum-based DUT (Dresden University of Technology) metal organic frameworks were synthesized, and their structural and chemical properties were exploited for the cycloaddition reaction of CO2 and epoxide under solvent-free condition. Both the catalysts have the same supramolecular architecture but different ligands. DUT-5 (Al(OH)(bpdc), bpdc = 4,4′-biphenyldicarboxylate) has a higher number of acidic and basic sites and larger BET surface area and specific pore volume compared with DUT-4 (Al(OH)(ndc), ndc = 2,6-naphthalenedicarboxylate). The highly porous DUT-5 exhibited better catalytic conversion of epichlorohydrin (ECH) than DUT-4, with >99 % selectivity in the presence of tetrabutylammonium bromide (TBAB). Short linkered MIL-53 (MIL = Materials Institute Lavoisier) (Al(OH)(bdc), bdc = 1,4-benzenedicarboxylate) exhibited lower ECH conversion compared with DUT-4 and DUT-5, even though all the catalysts possessed the same crystal structure. DUT catalyst could be recycled at least five times without any noticeable loss in the ECH conversion. In addition, the mechanism for the DUT-5/TBAB mediated cycloaddition of CO2 to ECH, affording the five‐membered ECH carbonate, has been investigated in detail using the density functional theory. The energy barrier for the ECH ring opening in the presence of DUT-5/TBAB (15.14 kcal/mol) is significantly lower than those of un-catalyzed (61.96 kcal/mol) and TBAB-catalyzed (39.60 kcal/mol) reactions, clearly showing the vital role of the Al3+/Br− bifunctional catalyst system.

Synthesis, Characterization and Enzyme Inhibition Activity of Organophosphorus Trichalcones Containing Core-Phosphate Moiety

Facile synthesis of various organophosphorus trichalcones, possessing substantial insecticidal activity, by using tris(4-acetylphenyl)-phosphate (3) and substituted benzaldehydes as a precursor has been reported. Key precursor 3 has been prepared under mild conditions in presence of tetrabutylammonium bromide (TBAB) as a phase transfer catalyst. All the synthesized compounds (5a-h) were screened for their antibacterial activity and inhibition of α-amylase of insect pest, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionadeae). Biological activity evaluation study revealed that among all the compounds screened, compound 5g found to have promising inhibition of α-amylase of insect pest, Tribolium castaneum. All the synthesized compounds revealed insignificant antimicrobial activity against pathogenic bacteria even at 500 μg/mL.