Melting Point Measurements Research Articles

ONE-POT DIASTEREOSELECTIVE SYNTHESIS OF CHIRAL TRICYCLIC l-CYSTEINE AND d-PENICILLAMINE DERIVATIVES: A LABORATORY EXPERIMENT

A one-pot diastereoselective synthesis of thiazolidine-ring fused systems derived from enantiomerically pure amino acids, L-cysteine or D-penicillamine, and achiral succindialdehyde is described as an experiment to be carried out by upper-division undergraduate students in a laboratory classroom. Reactions were performed under mild conditions, the products were isolated through simple experimental procedures and fully characterized. This study combines organic synthesis, determination of the purity of compounds (TLC analysis and melting point measurements), optical activity measurements as well as structural analysis (interpretation of 1D NMR and 2D NMR spectra). It offers a platform for the discussion of important organic chemistry concepts such as diastereoselectivity, kinetic control vs thermodynamic control and cyclization reactions via nucleophilic addition to imines/iminium cations.

Synthesis, Characterization and Antimicrobial Activities of Cobalt(II), Nickel(II) and Copper(II) Complexes of Aroylhydrazone Mixed with Aspirin

Co(II), Ni(II), and Cu(II) complexes of aroylhydrazone mixed with aspirin were synthesized and characterized by percentage metal analysis, infrared and electronic spectroscopy, melting point, solubility, molar conductance and room temperature magnetic moment measurements. Infrared spectra data revealed that the aspirin behaved as a bidentate ligand with coordination via carboxylate and carbonyl groups while the hydrazine coordinated via the azomethine nitrogen atom and carbonyl oxygen atom in the aroylhydrazone. The room temperature magnetic moment and electronic spectral data that the metal complexes possessed octahedral geometry. The molar conductance measurements of all the metal complexes in DMF indicated that they are non-electrolytes. The in vitro antimicrobial activities studies showed that the Cu(II) complex had the best activity against tested bacteria; Streptococcus spp, B. subtlis and vibro spp with inhibitory zones range of 2.0 - 6.0 mm, while the Ni(II) complex showed considerable activity against gram negative bacteria; Shigella spp with inhibitory zone of 10.0 mm suggesting its potential as an antimicrobial agent.

Synthesis, structural investigation and biological application of new mono- and binuclear cobalt (II) mixed-ligand complexes containing 1,10-phenanthroline, acetamide and ethylenediamine

The intensive use of antibiotics has led to an increase of drug resistant bacteria against known antibiotics. To overcome the alarming problem of microbial resistance to antibiotics, the discovery of novel active compounds against new targets is a matter of urgency. Based on this, we report three new mixed ligand complexes of cobalt (II) viz. mononuclear ([Co(phen) 2 (Act)(H 2 O)]Cl 2 .H 2 O and [Co(phen) 2 (Act)(en)]Cl 2 ), and binuclear [Co 2 (phen) 4 (Act) 2 (en)]Cl 4 which were synthesized from CoCl 2 .6H 2 O, 1,10-phenanthroline monohydrate, acetamide and ethylenediamine. These complexes were characterized using spectroscopic (ESI-MS, ICP-OES, FT-IR, and UV-Vis), chloride determination as well as melting point and conductance measurement. Invitro antibacterial activity was also tested on two Gram positive ( Staphylococcus aureus , Streptococcus pyogenes ) and two Gram negative ( Escherichia coli and Klebsiella pneumoniae ) bacteria using disc diffusion method. The complexes performed well even against the Gram-negative bacteria. The antibacterial result was found comparable with the commercial drug Gentamicin even at lower concentration of complexes. Thus, the synthesized complexes may be considered as potential antibacterial agents after passing cytotoxicity testing.

Synthesis, Characterization and the Corrosion Inhibition Study of Two Schiff Base Ligands Derived From Urea and Thiourea and Their Complexes with Cu(II) and Hg(II) Ions

The research includes synthesis of [L1] and [L2] Schiff base ligands by the reaction of vanillin with urea and thiourea respectively in 2:1 mol ratio. The two ligands were reacted with CuII ion in 1:2 mol ratio and HgII ion in 1:1 mol ratio. The prepared compounds have been identified by FTIR, U.V-Vis, 1H-NMR (L1, L2 and HgII complex) spectroscopies, microelemental analysis (C.H.N.S), magnetic susceptibility measurements, atomic absorption, chloride content along with conductivity and melting point measurements. According to applied characterization methods, the proposed general formulas of CuII and HgII complexes were [Cu2LnCl4] and [HgLnCl]Cl, respectively, (where n = 1, 2). The ability of corrosion inhibition with two ligands and their cupper complexes has been studied in diluted hydrochloric acid media.

Synthesis, characterization, computational studies and biological activity evaluation of Cu, Fe, Co and Zn complexes with 2-butanone thiosemicarbazone and 1,10-phenanthroline ligands as anticancer and antibacterial agents.

Mixed-ligand metal (II) (M=Cu, Fe, Co and Zn) complexes containing 2-butanone thiosemicarbazone and 1, 10-phenanthroline have been synthesized and characterized by melting point, FT-IR, 1H-NMR, UV-spectrophotometry and molar conductance measurements. All the complexes were soluble in DMSO and DMF. They were thermally stable with high melting points. The computational studies of the complexes were also performed to assess toxicity potential, bioactivity score prediction and drug likeliness assessment based on various drug filters. All the complexes showed no Veber's violations whereas only Cu complex showed one Lipinski's violation. Almost all synthesized compounds were predicted to have no toxic effects. Some of them showed positive bioactivity as enzyme inhibitors. Molecular docking of the complexes was also performed against ribonucleotide diphosphate reductase (RR) and topoisomerase II (Topo II) for minimum binding energy (kcal/mol) calculations. Cu complex was found to have minimum binding energy (-101.13 kcal/mol) released on interaction with Topo II showing a high affinity towards the enzyme, whereas Fe complex had the lowest binding energy (-99.8349 kcal/mol) when docked with RR. The results were compared with two standard drugs i.e. doxorubicin HCl and tetracycline. The ligand was tested for its potential anticancer activity against MDA-MB-231 cell line using MTT assay. Antibacterial activity of the complexes was tested against Staphylococcus aureus and Escherichia coli using the disc diffusion method. Cu (II) complex showed maximum activity against the MDA cells and also exhibited mild antibacterial activity against S. aureus.

The synthesis and investigation of different cobaloximines by spectroscopic methods

In the present work, firstly a novel monoxime (1) and unsymmetric dioxime ligand (LH2) (2) derived from 4-(4-hydroxyphenyl)-2-butanone as ketone was prepared under optimum conditions. Then, the cobaloxime complexes [(LH)2ClCoB] (B = neutral base: 4-DAP = 4-(dimethylamino)pyridine, 4-HP = 4-hydroxypyridine, 4-CP = 4-chloropyridine, 4-MP = 4-methylpyridine, 4-EP = 4-ethylpyridine, 4-TBP = 4-tert-butylpyridine and P = pyridine) (3–9) with respect to varied axial groups were synthesized in a two-necked round-bottom reaction flask by direct contact of dioxime ligand (2), and different neutral base without special requirement of any additional chemical process. The prepared dioxime ligand (2) and its cobaloxime complexes (3–9) were characterized by means of NMR, FT-IR, UV–Vis and LC-MS spectroscopy, melting point and magnetic susceptibility measurements as well as elemental analysis. It is noteworthy that the coordination chemistry of this cobaloxime complexes is versatile, which is closely related to the nature of the unsymmetric dioxime ligand (2) derived from 4-(4-hydroxyphenyl)-2-butanone, as indicated by the results of the corresponding spectroscopic studies. Also, the spectroscopic results demonstrated that the proposed cobaloxime complexes are a six-coordinated species and octahedral geometry.

Formation, characterization and computational studies of Lumazine Schiff base Rhenium(III) and –(V) complexes with carbohydrazide moieties

In this research study, the formation of new rhenium(III) and –(V) complexes with multidentate lumazine Schiff bases with carbohydrazide moieties: cis-[ReOBr2(PPh3)(bzlm) (1) (Hbzlm = N’-(1-(1,2,3,4-tetrahydro-1,3,7-trimethyl-2,4-dioxopteridin-6-yl)ethylidene)benzohydrazide) and cis-[ReBr2(PPh3)(tplm) (2) (tplm = N’-(1-(1,2,3,4-tetrahydro-1,3,7-trimethyl-2,4-dioxopteridin-6-yl)ethylidene)thiophene-2-carbohydrazide). These diamagnetic rhenium complexes were characterized by FTIR, UV–Vis and 1H NMR spectroscopy, TOF-Mass spectrometry, melting point and molar conductivity measurements. Computational studies were employed to rationalize the diverse coordination modes of the lumazine Schiff base chelators in the oxorhenium(V) complex 1 and the oxo-free rhenium(III) complex 2.

Preparation, Characterization and Antimicrobial Activity of Schiff Base of (E) - N - (4-(Thiophen-2-ylmethyleneamino) Phenylsulfonyl) Acetamide Metal Complexes

Aim:Metal complexes of (E)-N-(4-(thiophen-2-ylmethyleneamino) phenylsulfonyl) acetamide (S.TH) Schiff bases derived from sulfacetamide (N-[4-(amino-phenyl) sulfonil] acetamide) and 2-thiophenecarboxaldehyde were synthesized and characterized.Methods and Results:The synthesized compositions have been characterized using different physico-chemical techniques. The investigation included elemental analysis, melting point measurements, proton NMR, UV spectroscopy, FT-IR, magnetic susceptibility, conductance measurements, mass spectral analysis, and inductively coupled plasma mass spectrometry (ICP-MS) for determining the concentrations of metal ions. The measured values for molar conductance indicated that the majority of the prepared complexes were nonelectrolytes. The biological activity of the prepared compositions has been investigated.Conclusion:Spectroscopic studies suggested that most of the complexes were coordinated in a regular octahedral arrangement where S.TH ligand and the central metal atom were coordinated through two N amino azomethine groups (−HC=N−) and two sulfur atoms of S thiophene rings in 2L:1M molar ratio. Complexes have shown a promising activity upon screening for the antibacterial characteristics, and antifungal (Aspergillus fumigatesandCandida albicans)

Novel coumarin rhenium(I) and -(V) complexes: Formation, DFT and DNA binding studies

Herein, we report the formation and characterisation of novel rhenium(I) and -(V) compounds with coumarin bidentate chelates: trans-[ReOBr2(PPh3)(hbc)] (1) (Hhbc = 7-(2-hydroxybenzylideneamino)-4-(trifluoromethyl)-2H-chromen-2-one), fac-[Re(CO)3Cl(aomc)] (2) (aomc = 7-(((2-amino-4-oxo-4H-chromen-3-yl)methylene)amino)-4-(trifluoromethyl)-2H-chromen-2-one) and fac-[Re(CO)3Cl(moac)] (3) (moac = 7-(((2-methoxy-4-oxochroman-3-yl)methylene)amino)-4-(trifluoromethyl)-2H-chromen-2-one). The coumarin free-ligands and the metal complexes 1–3 were characterized by NMR, UV–Vis and FTIR spectroscopy, melting point and molar conductivity measurements as well as time-of-flight mass spectrometry. Their structural elucidations were supported by the respective solid state structures of 1, Hhbc and moac. DNA binding studies conducted using the facial tricarbonylrhenium(I) complexes 2 and 3, revealed that they are DNA groove binders with intrinsic binding constants in the order of 105 and 104 M bp, respectively. This study was also complemented using density functional theory (DFT) and time-dependent DFT methods to attain a deeper understanding into the structural parameters, infrared and electronic spectra of these coumarin free-ligands and their metal complexes 1–3.

Synthesis, Characterization and Antimicrobial Properties of Pd(II), Cr(III), Ni(II) and Co(II) Metal Complexes of Aniline and Sulphadiazine Schiff Bases as mixed Ligands

Novel Pd(II), Cr(III), Ni(II) and Co(II) metal complexes of Schiff bases were synthesized from the condensation reaction between salicylaldehyde and aniline (L1) and sulphadiazine (L2). They were characterized using FTIR and UV-Visible spectroscopy and subjected to conductivity, melting point and solubility measurements. The complexes are non-toxic, non-electrolytic and stable solids. The involvement of the azomethine nitrogen in coordination with the metals was confirmed by the IR and UV results. They showed good inhibitory activities against various microorganisms.

Fluorescence, Biological Activity and Spectroscopic Studies of Azo-linked Schiff Base Ligand Type (ONO) and Its Complexes with CrIII, CoII NiII and CdII Ions

The precursor [W] [2-(2-(naphthalen-5-yl) diazenyl)-4-amino-3-hydroxynaphthalene-1sulfonic acid] was synthesized from reaction of diazonium salt with 1-amino-2-naphtol-4sulfonic acid. Then the tridentate Schiff base ligand type ONO was synthesized from the reaction of the precursor with salicyaldehyde in 1:1 mole ratio to produce the ligand H2L [2-(2-(naphthalen5-yl) diazenyl)-4-(2-hydroxynaphthalen-3-yl)methyleneamino)-3-hydroxy salicyalene-1-sulfonic acid],the reaction achieved in methanol as a solvent under reflux. Spectroscopic methods IR, U.V, 1H,13C-NMR was used to characterize the ligand. Complexes of [CrIII, CoII, NiII and CdII] ions were also prepared through reaction of ligand with metal salts in 2:1 mole ratio at reflux, using KOH as a base, ethanol as a solvent. Chloride content, molar conductivity and melting point measurements along with I.R and U.V-Vis, atomic absorption (A.A) spectroscopy were used to characterize the complexes.1H-NMR spectroscopy was used to characterize Cd complex. Thermal analysis was used to insure the presence of crystallized H2O molecule in the complexes structure. The following formula was proposed for Cr complex: K[Cr(L)2]. H2O, while CoII, NiII and CdII complexes have the K2[M(L)2].H2O formula. The biological activity of the prepared compounds was studied. Fluorescence properties of the prepared compounds were studied (at room temperature) which indicate that the ligand may behave as strong fluorescent emitter. The complexes also showed fluorescence characteristic with the ligand. The ligand revealed high relative intensity and its fluorescence peak were also shifted to the lower or higher wavelength when compared with the complexes.

Synthesis Structural and Spectroscopic Study for Pd (II) complexes with 4-aminoantipyrine and Sodium pyrophosphate.

Pd (II) complexes were synthesized from 4-Aminoantipyrine (4-AAP) as primary ligand, and disodium pyrophosphato as secondary ligands using metal: ligand in (1:1) mole ratio with molecular formula [Pd(4-AAP)Cl2],[Pd(4-AAP) (Pyph)]. These complexes were characterized by elemental microanalysis (C.H.N), (A.A), [I.R, (U.V–Vis), mass spectroscopy], along with molar conductivity, Chloride contents and melting point measurements. The ligands (4-AAP) and (Pyph) gave square planar geometrical formula with Pd (II). Rapid, simple, sensitive and validated spectrophotometric method has been described for the determination of palladium (II) using 4-aminoantipyrine. The complex product was quantitatively measured at 363nm and the reaction conditions were studied and optimized.

Heteropoly acid supported on activated natural clay-catalyzed synthesis of 3,4-dihydropyrimidinones/thiones through Biginelli reaction under solvent-free conditions

ABSTRACTDihydropyrimidinones/thiones (DHPM’s) have been prepared by one-pot condensation of methyl acetoacetate, aldehydes, urea/thiourea in the presence of heteropoly-11-tungsto-1-vanadophosphoric acid, H4[PVW11O40] · 32H2O, (HPV) supported on activated natural clay (HPVAC) under solvent-free reaction condition have been proposed. The DHPM derivatives were identified through elemental analysis and melting point measurements and characterized by FT-IR, 1H-NMR, 13C-NMR spectroscopic methods.

Separation Mechanism of Fatty Acids from Waste Cooking Oil and Its Flotation Performance in Iron Ore Desiliconization

Using the mixed fatty acids (MFA) produced by waste cooking oil as flotation collectors directly, the flotation effect is usually not satisfactory, especially at lower temperature, which may be due to the presence of large amounts of saturated fatty acids. In this study, waste cooking oil was separated into saturated fatty acids (SFA) and unsaturated fatty acids (UFA). The separation mechanism was studied by molecular simulation based on quantum and molecular mechanics. SFA and UFA were analyzed by iodine value, melting point measurement and Fourier transform infrared (FT-IR) spectroscopy to check the result of the separation. The micro-flotation and bench-scale flotation tests were performed to investigate the flotation differences between SFA and UFA. The results showed that the poor flotation performance of waste cooking oil was due to the large amount of SFA in presence. If the SFA was separated out, the TFe grade and recovery of the flotation concentrates would be increased by 4.09 and 2.70 percentage points, respectively and the SiO2 grade would be 4.03 percentage points lower at the same time. This study would provide technical supports and theoretical guidance for the waste cooking oil application in the field of mineral processing.

Synthesis and Spectroscopic Study for Pt (IV) Complexes with 4-Aminoantipyrine and Sodium Pyrophosphate

Pt (IV) complexes were synthesized from 4-Aminoantipyrine (4-AAP) as a primary ligand, and sodium pyrophosphate as a secondary ligand using metal: ligand in (1:1) mole ratio with molecular formula [Pt (4-AAP)Cl4],[Pt (4-AAP)(Pyph)Cl2]. These complexes were characterized by elemental microanalysis (C.H.N), (A.A), [I.R, (U.V–Vis), mass spectroscopy], along with molar conductivity, chloride contents and melting point measurements. The ligands (4-AAP) and (Pyph) gave octahedral geometry with Pt (IV) rapid, simple, sensitive and validated spectrophotometric method has been described for the determination of platinum (IV) using 4-aminoantipyrine. The complex product was quantitatively measured at 385nm and the reaction conditions were studied and optimized.

Optical Response of Poly (1,4-Phenylene-1,2-Di (P-Phenoxyphenyl) Vinylene) Towards Oxygen Gas

This research involved the synthesis of poly (1,4-phenylene-1,2-di (p-phenoxyphenyl) vinylene), dpop-PDV from di (p-phenoxybenzoyl) benzene compound as the monomer. The potential of the produced polymer as sensing reagent for O2 detection based on fluorescence quenching was studied. Di (p-phenoxybenzoyl) benzene was synthesised via the Friedel-Crafts benzoylationwith terephthaloydichloride and biphenylether as starting materials and anhydrous AlCl3 as the catalyst, while the dpop-PDV was synthesized via the McMurry coupling reaction. The polymerization was carried out in THF with TiCl4 and Zn as the catalyst and reducing agent respectively. Characterization on monomer and polymer had been carried out by using FTIR, GCMS, DSC, TGA, GPC and melting point measurement. Response of the polymer towards oxygen gas was described in terms of fluorescence spectra, repeatability, reproducibility and the response curve. Results obtained showed that the fluorescence intensity decreased upon exposure to O2 gas, indicating that the polymer was responsive to the presence of the O2 gas and the sample was found regenerable by flushing the polymer solution with N2 gas.

Isolation of berberine tannate using a chromatography activity-guided fractionation from root bark of Berberis hispanica Boiss. & Reut.

ABSTRACTRoot bark of Berberis hispanica Boiss. & Reut. constitutes an important source of alkaloids and is traditionally used in Algeria and Morocco in many herbal formulations particularly for the treatment of stomach infections and colon cancer. Activity-guided fractionation of Berberis extract is developed by step-gradient elution on column chromatography followed by preparative HPLC to isolate the most antistaphylococcal compound. Solvent extraction-activity screening indicates that ethanol should be used as the extracting solvent as it has exhibited the highest activity against Staphylococcus aureus(Rosenbach ATCC6538) followed by water extract, whereas no activity is recorded for acetone and hexane extracts. Screening of collected fractions from chromatographic separations indicates that the fraction presenting the highest antistaphylococcal activity is identified as berberine tannate by UV spectrum, melting point measurement and confirmed by liquid chromatography coupled to mass spectrometry (LC/MS). The minimal inhibition concentration value of berberine tannate against S. aureus is evaluated at 5 µg mL−1.

Synthesis of trans-4,5-Bis-dibenzylaminocyclopent-2-enone from Furfural Catalyzed by ErCl3·6H2O

An experiment exploring the chemistry of the carbonyl group for the one-step synthesis of trans-4,5-dibenzylaminocyclopent-2-enone is described. The reaction of furfural and dibenzylamine in the environmentally friendly solvent ethanol and catalyzed by the Lewis acid ErCl3·6H2O afforded the product in high yield (79–97%) with high purity by simple filtration. This experiment can be performed during a 3 h class, and requires only basic glassware without an anhydrous or inert atmosphere. It is suitable for use in introductory organic chemistry laboratories, where the purity of the product can be determined, using simple techniques such as TLC analysis and melting point measurement, as well as for more advanced classes allowing the consolidation of important reactivity features of the carbonyl group and the interpretation of the 1H NMR spectrum.

The Novel bis-dioxime-based and Boronic acid-capped Groups Containing Fe(II) and Co(II) Complexes: Synthesis, Characterization, and Spectroscopy

In the present work, firstly the novel mono oxime (1) and asymmetric dioxime ligand (LH 2 ) (2) derived 4′-hydroxyvalerophenone as ketone were prepared under optimum conditions. Then, the bis-dioxime-based and boronic acid-capped groups containing Fe(II) and Co(II) complexes [(L) 2 M(X) 2 (BA) 2 ] (3-6) (L= Dioxime, M = Fe(II) or Co(II), X= Cl 2 or H 2 O and BA = Butyl boronic acid (BBA) or Ferrocene boronic acid (FBA)) were synthesized in a two-necked round-bottom reaction flask by direct contact of dioxime ligand (2) , and different boronic acid with metal salts (FeCl 2 .4H 2 O or CoCl 2 ) without special requirement of any additional chemical process. The prepared ligands and its Fe(II) and Co(II) complexes were characterized by means of NMR spectra, FT-IR spectra, UV-Vis spectra, LC-MS, melting point and magnetic susceptibility measurements as well as elemental analysis. The spectroscopic results demonstrated that the proposed Fe(II) and Co(II) complexes are a six-coordinated species and octahedral geometry. The infrared spectra (FT-IR) of the Fe(II) and Co(II) complexes indicated the characteristic peak at range 1208-1217 cm -1 cm corresponding υ(B-O) stretching.

Synthesis and characterization of a new copper(II) polymer containing a thiocyanate bridge and its application in dopamine detection

Reaction of bis(3,5-dimethyl-1-pyrazolyl)methane (L) with CuCl2 and NaNCS yielded the new coordination polymer [Cu2(μ-SCN)3(L)2] (I), which was isolated as a brown and air-stable solid. The new compound was characterized by melting point measurement, elemental analysis, mass spectra, thermogravimetric analysis, magnetic moment, and Raman, Infrared and Ultraviolet/Visible spectroscopy. In addition, the structure of the compound was determined by single-crystal X-ray diffraction. As an application, the copper polymer was used to modify a fluorine-doped tin oxide (FTO) electrode covered with poly(3,4-ethylenedioxythiophene). This electrode was tested for the detection of dopamine (DA) in the presence of ascorbic acid (AA) in a PBS solution at pH 7.4. The presence of the new copper polymer diminished the charge transfer resistance of the surface allowing the detection of DA by differential pulse voltammetry. The calibration curves for DA showed two linear ranges from 0.6 to 9.0μM and from 10.0 to 200.0μM. The sensitivity of the lowest concentration range was 0.336μAμM−1cm−2.