Presence Of 1-methylimidazole Research Articles

A novel Schiff base ligand and its metal complexes: Synthesis, characterization, theoretical calculations, catalase-like and catecholase-like enzymatic activities

In this study, a new Schiff base (H2L), which has not been recorded in the literature, and its metal complexes with general formula [ML].(H2O) [M: Cu(II) and Mn(II)] were synthesized and their structures were elucidated. Techniques such as 1H- and 13C-NMR, FT-IR, UV–vis, TG-DTG, molar conductivity, magnetic susceptibility, ICP-OES, and elemental analysis were used to characterize the structures of the Schiff base and metal complexes. According to the analysis's findings, the complexes' metal:ligand ratio was 1:1. Additionally, the 6-311G(d,p) and LANL2DZ basis sets of the DFT/B3LYP method were used to calculate the optimized molecular geometries of the H2L and its metal complexes, respectively. Additionally, the synthesized compounds' molecular electrostatic potential (MEP) diagrams, frontier molecular orbitals (HOMO-LUMO), chemical shift values for the 1H- and 13C-NMR, vibrational frequencies, and wavelengths of electronic transitions were all determined. Experimentally obtained results were verified with theoretical data that matched well. [CuL].(H2O) and [MnL].(H2O) were examined for their catalase-like and catecholase-like enzymatic activities using volumetric and spectrophotometric techniques, respectively. For this objective, the catalytic activities of the synthesized molecules in the disproporsion reaction of H2O2 in the presence of 1-methylimidazole and the oxidation reaction of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in aerobic medium were investigated. According to the enzyme-like studies, [MnL].(H2O) was more catalytically active than [CuL].(H2O) in both of the mentioned reactions.

Complete Chemical Synthesis of Minimal Messenger RNA by Efficient Chemical Capping Reaction.

Site-specific chemical modification of mRNA can improve its translational efficiency and stability. For this purpose, it is desirable to develop a complete chemical synthesis method for chemically modified mRNA. The key is a chemical reaction that introduces a cap structure into the chemically synthesized RNA. In this study, we developed a fast and quantitative chemical capping reaction between 5'-phosphorylated RNA and N7-methylated GDP imidazolide in the presence of 1-methylimidazole in the organic solvent dimethyl sulfoxide. It enabled quantitative preparation of capping RNA within 3 h. We prepared chemically modified 107-nucleotide mRNAs, including N6-methyladenosine, insertion of non-nucleotide linkers, and 2'-O-methylated nucleotides at the 5' end and evaluated their effects on translational activity in cultured HeLa cells. The results showed that mRNAs with non-nucleotide linkers in the untranslated regions were sufficiently tolerant to translation and that mRNAs with the Cap_2 structure had higher translational activity than those with the Cap_0 structure.

Dual curing of an epoxy resin with dicarboxylic acids

In this work, we have studied the preparation and characterization of a new family of thermosets based on off-stoichiometric diacid-epoxy formulations in the presence of 1-methylimidazole as initiator. Tri-glycidyl para-amino phenol has been used as epoxy resin and isophthalic (AIFT), and terephthalic (ATFT) acids have been used as diacids. The curing has been analyzed isothermally at different temperatures by calorimetry, using an isoconversional method and the Sestak–Berggren equation to determine the activation energy, the frequency factor, and the reaction orders. The thermal–mechanical properties of the partially cured and fully cured materials were also determined by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The analysis of the isothermal curing by infrared spectroscopy by Fourier transform allowed monitoring the reacting groups during the process. Two peaks appeared during the isothermal curing in the DSC. The first one is associated with the reaction of the carboxylic groups of the diacids with the epoxy groups, and the second one is related to the homopolymerization of the excess of epoxy groups. ATFT reacts less with the epoxy groups than AIFT, but accelerates more the homopolymerization and the isothermal curing ends earlier than in the systems with AIFT. Incomplete solubilization of the diacid monomers led to incomplete carboxylic reaction and excess of epoxy homopolymerization. In addition, two phases could be observed.

Synthesis, characterization, DFT calculations and catalase-like enzymatic activities of novel hexadentate Schiff base and its manganese complexes

We reported the synthesis of the manganese(II) and manganese(III) complexes of a novel hexadentate Schiff base ligand (HBME) (1) obtained from the condensation of triethylenetetramine and 2 equiv. of 1-(biphenyl)-2-hydroxyimino-2-(morpholino)-1-ethanone. Hexadentate Schiff base ligand reacted with manganese(II) perchlorate or manganese(III) acetate and sodium azide, to give rise to a series of mono and dinuclear complexes [Mn(BME)2tren)] (2), [Mn2(BME)2tren(N3)2] (3) and [Mn2(BME)2tren(N3)4] (4). Synthesized molecules were characterized by elemental analyses, ICP-MS, spectroscopic studies, thermal analyses, molar conductivity and magnetic susceptibility measurements. The quantum chemical calculations of the HBME and complexes (2–4) were performed in the ground state using the DFT of B3LYP level with 6-311G(d,p) and LanL2DZ basis sets, respectively. 1H and 13C NMR chemical shifts were calculated by using the gauge independent atomic orbital (GIAO) method and the electronic properties such as HOMO-LUMO energies were determined by the time-dependent DFT approach. The calculated spectroscopic values for the HBME were in very good agreement with experimental ones. Furthermore, catalytic activity of the complexes for the disproportionation of hydrogen peroxide was also investigated in the presence of 1-methylimidazole. All the complexes displayed catalytic activity for the disproportionation of H2O2 significantly, but the activities of the (3) and (4) were relatively higher than the other molecules.

Pressure sensitive adhesives with post-crosslinking ability based on acrylic dispersions obtained from solvent-borne copolymers

This work presents a novel aqueous dispersion prepared from a solvent-borne acrylic copolymer mixture containing carboxylic acid groups for the first copolymer and epoxy groups for the second copolymer. The aim of this work was to test the suitability of the presented dispersion for the preparation of pressure sensitive adhesives (PSA) with post-crosslinking ability. A monomodal particle size distribution was obtained and a successful coemulsification of both copolymers into one particle was proved, although the epoxy containing polymer did not bear carboxylic acid groups. Storage of the dispersion led to intraparticular crosslinking inside the particles, which produced an increase in the shear of the PSA. Post-crosslinking ability was shown for the PSA of the unaged and aged dispersions in the presence of 1-methylimidazole and led to a major increase in shear but did not lead to a considerable decrease in peel. Probe-tack enabled a fast detection of post-crosslinking because of the appearance of a plateau formation in probe-tack curves. The adhesive properties before and after crosslinking demonstrate the potential of the presented dispersion, which yields novel PSA for applications which need high shear but also sufficient peel.

Synthesis, characterization, theoretical calculations and enzymatic activities of novel diimine-dioxime ligand and its homodinuclear Cu(II) complex

A novel ligand [2-(biphenyl-4-yl)-2-(2-(1-(biphenyl-4-yl)-2-(hydroxyimino) ethylideneamino)ethylimino)acetaldehyde oxime] (BPHEO) and its homodinuclear Cu(II) complex [Cu2(L) (H2O) (phen)](ClO4)2 were prepared starting from biphenyl and characterized by different physical techniques. Elemental analysis, ICP-OES, FT-IR, UV–vis molar conductivity, magnetic moment measurements and thermal analyses studies were used for the characterization of the complexes. The free ligand was also characterized by 1H and 13C NMR spectra. Elemental analyses, stoichiometric and spectroscopic data of the metal complex indicated that the metal:ligand ratio of homodinuclear Cu(II) complex was found to be 2:1. The structural and vibrational spectroscopic data of the BPHEO and its homodinuclear Cu(II) complex were calculated and confirmed by DFT method. Chemical shifts (1H and 13C NMR) of the ligand were also calculated using the gauge-independent atomic orbital (GIAO) method. Furthermore the synthesized complex was tested as catalyst for the catalytic oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone at aerobic medium (catecholase-like activity) and disproportionation of hydrogen peroxide to the water and molecular oxygen in the presence of 1-methylimidazole (catalase-like activity). It was found that the complex showed moderate catalytic activity and suitable as a catalyst for the selected enzymatic reactions.

Solvent-free synthesis of tris(4-hydroxybutyl acrylate) phosphate in the presence of 1-methylimidazole

In this paper, we present the synthesis of tris(4-hydroxybutyl acrylate) phosphate using 1-methylimidazole as acid scavenger for hydrochloric acid by-product, when an ionic liquid is formed. The synthesis was performed in the absence of any organic solvent. The yield is 83% for ester. The phosphate was characterized by 1H–31P NMR and FTIR. The obtained phosphate is appropriate monomer for UV curing in the presence of photoinitiator. The obtained polymer was characterized by thermal analysis and LOI. The results showed good thermal stability and flame retardancy of UV-cured polymer.

Study of the hydrophobization of TEMPO-oxidized cellulose gel through two routes: amidation and esterification process

In this paper, we studied the hydrophobization of TEMPO-oxidized cellulose gel (TOCgel) by covalent coupling of long carbon chains via esterification and amidation processes. In this context, amidation process was achieved by covalent coupling of stearylamine (SA) on the carboxyl moieties of TOCgel using carbodiimide and hydroxysuccimide as catalyst and amidation agent. In parallel, esterification process was realized by grafting of alkyl ketene dimer (AKD) on the hydroxyl groups of TOCgel in the presence of 1-methylimidazole as a promoter. The grafting state of the final products obtained under heterogeneous conditions was confirmed by fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), transmission and scanning electron microscopy, and contact angle measurement (CAM). The hydrophobic behavior of the obtained products was discussed based on the results of CAM and absorption rate of water drop in their film surface. FTIR and XPS results indicated the formation of amide bonding for the SA-g-TOCgel (amidation), and β-keto ester linkages for the AKD-g-TOCgel (esterification). As confirmed by CAM, the both chemical treatments enhanced the transition hydrophilic/hydrophobic behavior of the TOCgel fibers. It appeared also that CA values of grafted samples showed a slightly greater hydrophobicity of AKD-g-TOCgel (115° ± 2°) relatively to SA-g-TOCgel (102° ± 2°). However, the absorption rate of water drop seems to be relatively faster for AKD-g-TOCgel than for SA-g-TOCgel. Indeed, the water resistance of amidation product could be due to the high graft efficiency obtained (46.3 %) in comparison with that of the esterification product (30 %). In parallel, this result was confirmed by the dispersion test of modified TOCgels in hexane solvent which indicated clearly the high stable dispersion of SA-g-TOCgel obtained through the amidation process. Moreover, TGA result demonstrated that the thermal stability was found to be slightly higher for SA-g-TOCgel than for AKD-g-TOCgel. Finally, the excellent hydrophobic properties of modified TOCgel material could be suitable to be used as reinforcement for nonpolar polymer matrices in industrial applications.

Gas chromatography-mass spectrometric determination of ivermectin following trimethylsilylation with application to residue analysis in biological meat tissue samples

A gas chromatography-mass spectrometric (GC-MS) method utilizing electron impact ionization has been developed for the quantitation of the antiparasitic agent, ivermectin (IVM). The approach is based upon the pre-column derivatization of IVM by reaction with N,O-bis(trimethylsilyl)tri-fluoroacetamide (BSTFA) in the presence of 1-methylimidazole as catalyst and carbon tetrachloride as solvent to form the trimethylsilyl (TMS) derivative of IVM (IVM-TMS) prior to injection into the GC-MS system. The derivatization reaction is complete within 5.0 min at room temperature and allows the GC-MS determination of IVM. A limit of detection for IVM of 0.67 ng g−1 was achieved (via monitoring the peak with m/z = 185 in the selective ion mode and benzophenone-d10 as the internal standard). The method was utilized with success for the determination of IVM in spiked horse meat samples yielding recoveries very similar to that obtained using a reference liquid chromatography-mass spectrometric method (LC-MS). In addition, this GC-MS method can be employed to determine not only IVM but also other related macrolide veterinary drugs such as eprinomectin and moxidectin which are often administered along with IVM. Detection limits of 3.72 and 5.44 ng g−1 were obtained for eprinomectin and moxidectin, respectively.

Photoinduced reactions of cis,trans,cis-[Pt(IV)(N3)2(OH)2(NH3)2) with 1-methylimidazole.

The photodecomposition of cis,trans,cis-[Pt(IV)(N(3))(2)(OH)(2)(NH(3))(2)] in phosphate buffered saline (PBS), as well as in the presence of 1-methylimidazole (1-MeIm), induced by UVA light (centred at lambda=365 nm) has been studied by multinuclear NMR spectroscopy. We show that photoreduction, photoisomerisation and trans-labilisation pathways are involved. The photodecomposition pathway in PBS, which involves azide release, as detected by (14)N NMR spectroscopy, appears to differ from that in acidic aqueous conditions, under which N(2) is a product. A number of trans-{N-Pt(II)-NH(3)} species were also observed as photoproducts, as well as the release of free ammonia with a corresponding increase in pH. Oxygen was also detected as a product in solution. In the presence of 1-methylimidazole, surprisingly the major photoproduct was the tetra-substituted Pt(II) complex [Pt(II)(1-MeIm-N(3))(4)](2+) (structure confirmed by crystallography), even at a Pt/1-MeIm molar ratio of 1:1, together with cis- and trans-[Pt(II)(NH(3))(2)(1-MeIm-N(3))(2)](2+) as minor products. In these photoinduced 1-MeIm reactions, free ammonia, azide and oxygen were also detected. The results from this study illustrate that photoinduced reactions of platinum complexes can lead to novel reaction pathways, and therefore to new cytotoxic mechanisms in cancer cells.

Efficient method for the direct preparation of aryl carboxylates from carboxylic acids using tosyl chloride under solvent-free conditions

A simple, clean and efficient solvent-free procedure for the preparation of aryl carboxylates is described from the direct reaction of carboxylic acids and phenols, in the presence of 1-methylimidazole as base and tosyl chloride (TsCl) as coupling agent. This method can be easily applied for different substituted phenols and carboxylic acids. It can also be applied for the selective acylation when other functional group such as hydroxyl is present on phenol ring.

Practical Synthesis of a Peptide Deformylase (PDF) Inhibitor

A practical chromatography-free synthesis of an N-formylated hydroxylamine peptide deformylase inhibitor LCD320 is described. A diastereoselective Michael reaction of (4S)-3-[2-(cyclobutylmethyl)-1-oxo-2-propenyl]-4-(phenylmethyl)-2-oxazolidinone with O-benzyl hydroxylamine was used to establish the key stereogenic center. We found that traces of residual Li+ from a previous step had a great impact on the diastereoselectivity of this reaction. A very efficient amidation coupling reaction of proline derivative (2S,4R)-4-fluoro-1,2-pyrrolidinedicarboxylic acid 1,1-dimethylethyl ester with weakly nucleophilic 3-pyridazinamine using methanesulfonyl chloride in the presence of 1-methylimidazole in DMF was also developed that proceeded without racemization.

A facile synthesis of fluorinated alkoxytrimethylsilanes using 1-methylimidazole as an acid scavenger

Fluorinated alkoxytrimethylsilanes (R fCH 2OSiMe 3), potential candidates for the third-generation cleaning agents, were synthesized in high yields over 95% from the reaction of chlorotrimethylsilane and fluorinated alcohol (R fCH 2OH) in the presence of 1-methylimidazole. Elemental and 1H NMR spectroscopic analysis showed that the reaction proceeds through the formation of an intermediate, 3-methyl-1-trimethylsilylimidazolium chloride.

An angular trinuclear copper(II) complex as a model for the active site of multicopper oxidases

A new angular trinuclear copper(II) complex [Cu 3L 1L 2(1-MeIm)(H 2O)](ClO 4) ( 1), where H 3L 1 and H 2L 2 are penta and tetra-dentate Schiff base ligands, is prepared from a reaction of [CuL 2] and [Cu 2L 1(μ-Br)] in the presence of 1-methylimidazole (1-MeIm) and isolated as a perchlorate salt. The complex which crystallizes in the monoclinic space group P2 1/ n shows the presence of a discrete angular trinuclear copper(II) core in which the monomeric precursor is linked with the dimeric precursor through phenoxo bridges. The core structure resembles well with the active site structure of blue multicopper oxidases. The Cu⋯Cu separations of ca. 3.3 Å in the angular unit is 0.4 Å shorter than those observed in the active site of the oxidized form of ascorbate oxidase. The complex displays a visible band at 620 nm ( ε=500 M −1 cm −1) in DMSO. It shows magnetic moment values of 3.07 and 2.18 μ B at 300 and 18 K, respectively, for the Cu 3 cluster. The complex models the structural and magnetic properties of the trinuclear active site of blue copper oxidases.

Binding and activation of aromatic molecules by a molybdenum pi-base.

Compounds having the form TpMo(NO)(1-methylimidazole)(eta(2)-L(pi)) (Tp = hydridotris(pyrazolyl)borate; L(pi) = cyclohexene, naphthalene, furan, thiophene, and acetone) were synthesized in 31-41% yield by the reduction of TpMo(NO)Br(2) in the presence of 1-methylimidazole and the respective pi-acidic organic ligand. The structure of the naphthalene complex was confirmed by single-crystal X-ray diffraction. Degradation studies showed the bound aromatics to have half-lives of 37-236 h in acetone solution at 20 degrees C. A tandem addition across the bound ring of the naphthalene complex yielded a free 1,2-dihydronaphthalene in 80% yield following decomplexation.

Synthesis of Novel Biodegradable Poly(Ester-Anhydride)s

Poly(ϵ-caprolactone)s containing one and variable numbers of anhydride functions along the polymer backbone were synthesized and characterized. The inclusion of a single anhydride unit involved the coupling of monofunctional carboxylic acid-terminated prepolymers using diphenyl chlorophosphate. The prepolymers were produced using stannous octoate as catalyst and ethanol as the initiator, yielding mono-functional hydroxyl-terminated intermediates which were reacted with succinic anhydride in the presence of 1-methylimidazole. Diphenyl chlorophosphate was then added to a solution of the carboxylic acid-terminated prepolymer and triethylamine in 1,2-dichloroethane, and the reaction was carried out for 5 hours at room temperature to yield a polyester containing a single anhydride unit. The synthesis of polymers containing a variable number of anhydride linkages per chain was carried out in a similar manner using difunctional carboxylic acid-terminated prepolymers as chain-extending segments, and monofunctional carboxylic acid-terminated prepolymers as end-capping units. The difunctional hydroxyl-terminated poly(ϵ-caprolactone) prepolymers were produced using diethylene glycol as the initiator, and then reacted with succinic anhydride to form difunctional carboxylic acid-terminated prepolymers.

Depurination of Adenosine and Deoxyadenosine Monophosphates in the Hemin-hydroperoxide System.

The adenine base was liberated by the oxidative cleavage of the N-glycosidic bond of substrates (5'- and 3'-AMP, 5'- and 3'-dAMP) in the hemin-cumene hydroperoxide system, which was accelerated in the presence of 1-methylimidazole.

Catalytic oxidation of benzylic amines to imines by M(TPP)CL (M = Fe, Mn) followed by reduction to secondary amines

The oxidation of benzylic amines ArCH 2NH 2 ( 3–10) to the corresponding imines ArCH = NCH 2Ar ( 3a–10a) has been observed in catalytic systems containing Bu tOOH and metallo(III) tetraphenyl porphyrins (metallo = Fe, Mn) in the presence of 1-methyl imidazole as axial ligand. Secondary amines, (ArCH 2) 2NH ( 3b–10b) have been obtained by further reduction of the reaction products with NaBH 4.

Reaction of carbon dioxide with tetra-t-butylphthalocyaninato-aluminium(III)-ethylate or -ethoxide

Abstract By bubbling carbon dioxide through a chloroform solution of the title complex in the presence of 1-methylimidazole, carbon dioxide was inserted between the AlO bonding, which was confirmed by 1 H NMR and IR spectra.

Cycloaddition of carbon dioxide to propylene oxide catalysed by tetra- t-butylphthalocyaninatoaluminium(III) chloride

Cyclic propylene carbonate was obtained from propylene oxide in the presence of 1-methylimidazole with atmospheric carbon dioxide at room temperature using tetra- t-butylphthalocyaninatoaluminium(III) chloride as catalyst. The reaction proceeded via insertion of propylene oxide and carbon dioxide between the aluminium(III) ion and the axial ligand. Coordination of the base such as 1-methylimidazole to the aluminium(III) weakens the bonding between the aluminium(III) and the axial ligand, promoting the insertion of carbon dioxide.