Complex In Methanol Solution Research Articles

Analyses of the brominated vegetable oil in soft drinks using gas chromatography–flame ionization detector and atmospheric pressure gas chromatography–quadrupole/time-of-flight mass spectrometry

Herein, a new method for quantifying the brominated vegetable oil content in commercial soft drinks was developed, which accelerated the sample preparation process and improved analytical efficiency. First, simple and accurate chromatographic separation techniques were performed using a VF-5ht column for both GC-FID (quantitative) and APGC-QTOF (qualitative) analyses. The samples were subjected to chromatography on a reversed-phase solid-phase extraction cartridge. (PoraPak™RxnRP). Transesterification using a boron trifluoride methanol complex in methanol solution was performed. When validating this method, the analyte recovery percentages were between 82.2% and 99.9%, and the recovery and standard deviation of repeatability values were between 1.2% and 3.5%. Using an isotope library, the bromostearic acid methyl esters (9,10-dibromostearic acid methyl ester, 9,10,12,13-tetrabromostearic acid methyl ester, and hexabromostearic acid methyl ester) in the sample mixtures were qualitatively confirmed via APGC-QTOF. A novel aqueous ammonium adduct, which has not been previously reported, was also confirmed. These results indicated that this new method was simple, accurate, and also allowed for precise qualitative and quantitative confirmation as well as high reproducibility.

Synthesis, Characterization, and Low-Toxicity Study of a Magnesium(II) Complex Containing an Isovanillate Group.

The beneficial effect of polyphenols and magnesium(II) against oxidative stress motivated our research group to explore the antioxidant activity of phenMgIso, an aqueous soluble magnesium(II) complex containing 1,10-phenanthroline (phen) and isovanillic acid (Iso) as ligands. Combined electrospray ionization–mass spectrometry and DOSY-NMR techniques identified two complexes in methanolic solution: hexacoordinated [Mg(phen)2(Iso)]+ and tetracoordinated [Mg(phen)(Iso)]+. The cyclic voltammogram of phenMgIso in the anodic region showed a cyclic process that interrupts the isovanillic acid degradation, probably by stabilization of the corresponding phenoxyl radical via complexation with Mg(II), which is interesting for antioxidant applications. phenMgIso competes with 2,2,6,6-tetramethylpiperidine by 1O2 with IC50(1O2) = 15 μg m–1 and with nitrotetrazolium blue chloride by superoxide ions (IC50(O2•–) = 3.6 μg mL–1). Exposure of both zebrafish (2 mg L–1) and wistar male rats (3 mg kg–1 day–1 dose for 21 days) to phenMgIso does not cause mortality or visual changes compared with the respective control groups, thus phenMgIso could be considered safe under the conditions of this study. Moreover, no significant changes in comparison to both control groups were observed in the biochemical parameters on the brain-acetylcholinesterase activity, digestive tract enzyme catalase, and glutathione-S-transferase. Conversely, the performance of superoxide dismutase activity in wistar male rats increased in the presence of a complex, resulting in enhanced capacity of rats for superoxide radical enzymatic scavenging. The synergistic action of phenMgIso may be explained by the strong electrostatic interaction between Mg(II) and the O,O(phenolate) group, which makes the Iso ligand easier to oxidize and deprotonate, generating a cyclic stable species under oxidative conditions.

Zinc(II) halide complexes with 2-methoxyaniline ligand: Synthesis, characterization, thermal analyses, crystal structure determination and luminescent properties

Three new mononuclear zinc(II) complexes, [Zn(2-MeO-C6H4NH2)2X2] (X is Cl in 1, Br in 2 and I in 3), were prepared from the reactions of ZnX2 with 2-methoxyaniline (2-MeO-C6H4NH2) ligand in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurements by slow evaporation of methanol solution at room temperature. The three complexes were thoroughly characterized by thermogravimetric analysis, elemental analysis (CHNO), spectral methods (IR, UV–Vis, 13C{1H}NMR, 1H NMR and luminescence), and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the zinc(II) cation is four-coordinated in a distorted tetrahedral configuration by two N atoms from two 2-methoxyanyline ligands and two halide anions. Also, in these complexes intermolecular interactions, for example NH⋯X hydrogen bonds (in 1–3), CH⋯X hydrogen bonds (in 3), CH⋯π interactions (in 1 and 2) and π⋯π interactions (in 3), are effective in the stabilization of the crystal structures. In addition, the luminescence spectra of all complexes in methanolic solution show that the intensity of their emission bands is stronger than that for free 2-methoxyaniline ligand.

Magnetized property effect of a non-aqueous solvent upon complex formation between kryptofix 22DD with lanthanum(iii) cation: experimental aspects and molecular dynamics simulation

The variation of molar conductance versus mole ratio for (kryptofix 22DD·La)3+ complex in methanol solution at different temperatures is in accordance with the variation of pair correlation function of oxygen atoms.

A quantum mechanics, molecular dynamics and EXAFS investigation into the Hg2+ ion solvation properties in methanol solution

The coordination properties of the Hg2+ ion in methanol solution have been investigated by combining extended X-ray absorption fine structure (EXAFS) spectroscopy and Quantum Mechanics/Molecular Dynamics (QM/MD) calculations. An effective Hg–methanol two-body potential has been generated from QM calculations in which the effect of bulk solvent is accounted for by the polarizable continuum model (PCM). This effective potential is then used in the MD simulation to obtain the structural and dynamic properties of the solution, and the reliability of the entire procedure is assessed by comparing the theoretical structural results with the EXAFS experimental data. The outstanding outcome of this work is that the Hg2+ ion forms a stable sevenfold complex in methanol solution, where the first shell solvent molecules are arranged in a distorted pentagonal bipyramid geometry. In this geometry five methanol molecules are not located on the equatorial plane, but are displaced above and below the plane, forming a “crown” around the ion. The Hg2+ first coordination shell has been found to be very flexible, and several transitions among coordination numbers of 7, 8 and 6 are observed during the simulation.

The co-ordination chemistry of bis(2,2′-bipyrid-6′-yl)ketone with first row transition metals: The reversible interconversion of a mononuclear complex and a dinuclear hemiketal containing species

Bis(2,2'-bipyrid-6'-yl)ketone has been shown to co-ordinate to Zn(II) to form either a dinuclear hemiketal complex in methanol solutions or mononuclear complexes in acetonitrile. The ligand readily complexes to the late transition metals in acetonitrile to yield mononuclear complexes (Mn(II), Co(II), Ni(II),Zn(II) and Cd(II)) however for Fe(II) only dinuclear complexes [Fe(2){(2-bipy)(2)C(OMe)O(-)}(2)][ClO(4)](2) could be isolated. The solid state structures of the mononuclear complexes exhibit varying degrees of distortion compared to an anticipated planar array of bipyridyl donors.

A thermodynamic study of complexation of 18-crown-6 with Zn2+, Tl+, Hg2+ and $$ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $$ cations in acetonitrile-dimethylformamide binary media and study the effect of anion on the stability constant of (18C6-Na+) complex in methanol solutions

The equilibrium constants and thermodynamic parameters for complex formation of 18-crown-6(18C6) with Zn2+, Tl+, Hg2+ and \( {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} \) cations have been determined by conductivity measurements in acetonitrile(AN)-dimethylformamide(DMF) binary solutions. 18-crown-6 forms 1:1 complexes [M:L] with Zn2+, Hg2+ and \( {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} \) cations, but in the case of Tl+ cation, a 1:2 [M:L2] complex is formed in most binary solutions. The thermodynamic parameters (\( \Delta {\text{H}}^{ \circ }_{{\text{c}}} \) and \( \Delta {\text{S}}^{ \circ }_{{\text{c}}} \)) which were obtained from temperature dependence of the equilibrium constants show that in most cases, the complexes are enthalpy destabilized but entropy stabilized and a non-monotonic behaviour is observed for variations of standard enthalpy and entropy changes versus the composition of AN/DMF binary mixed solvents. The obtained results show that the order of selectivity of 18C6 ligand for these cations changes with the composition of the mixed solvent. A non-linear relationship was observed between the stability constants (logKf) of these complexes with the composition of AN/DMF binary solutions. The influence of the \( {\text{ClO}}^{ - }_{{\text{4}}} \), \( {\text{NO}}^{ - }_{{\text{3}}} \) and \( {\text{Cl}}^{ - } \) anions on the stability constant of (18C6-Na+) complex in methanol (MeOH) solutions was also studied by potentiometry method. The results show that the stability of (18C6-Na+) complex in the presence of the anions increases in order: \( {\text{ClO}}^{ - }_{{\text{4}}} \) > \( {\text{NO}}^{ - }_{{\text{3}}} \) > \( {\text{Cl}}^{ - } \).

A water‐soluble supramolecular‐structured photoinitiator between methylated β‐cyclodextrin and 2,2‐dimethoxy‐2‐phenylacetophenone

AbstractA water‐soluble supramolecular‐structured photoinitiator (SSPI) was synthesized by supramolecular self‐assembling between methylated β‐cyclodextrin (MβCD) and hydrophobic 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA). The structure of SSPI was characterized by X‐ray diffraction, FTIR, 1H NMR, UV–vis, and fluorescence spectra. The results indicated that MβCD and DMPA had formed 1 : 1 inclusion complex in methanol solution. The binding constant (K) for the complex was 7.51 × 102M−1. SSPI could be dissolved in water easily and its water‐solubility was 15.3 g/100 mL. SSPI was the more efficient photoinitiator than DMPA for the photopolymerization of acrylamide (AM) in homogeneous aqueous system. The conversion for photopolymerization of trimethylolpropane triacrylate system initiated by SSPI was similar to that initiated by DMPA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

A New Two‐Dimensional Coordination Polymer of Mercury(II) with very High Thermal Stability

AbstractA 2D HgII coordination polymer containing ligands 1,2,4‐triazole (Htrz) and thiocyanate, [Hg(μ3‐trz)(SCN)]n (1) has been synthesized and characterized by elemental analysis and IR spectroscopy. The single‐crystal X‐ray data show the coordination number of Hg atoms is four and the ligand trz− acts as a three‐fold donor. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses. The composition and formation of the complex in methanol solution were found to be in support of its solid state structure.

Electrophosphorescent divalent osmium and ruthenium complexes: A density functional theory investigation of their electronic and spectroscopic properties

Structures of divalent osmium and ruthenium complexes of [M(bpy) 3] 2+, [M(bpy) 2P 2] 2+ and [M(dpb) 2P 2] 2+ (M=Ru, Os, bpy=2,2′-bipyridine, dpb=4,4′-diphenyl-2,2′-bipyridine, P 2=cis-1,2-bis(diphenylphosphino)ethylene) in the ground and the lowest triplet states were fully optimized with density functional theory. The features of the absorption bands and phosphorescent emission from the lowest triplet state for the complexes have been described by time-dependent density functional theory. The [Os(bpy) 3] 2+ complex in methanol solution exhibits two strong absorption bands at ∼495 and ∼445 nm, which are well reproduced by the present calculations. There is one absorption peak observed at 440-460 nm for the divalent Ru polypyridyl complexes in methanol solution, which is close to the TDDFT calculated values of 415–440 nm for the complex of [Ru(bpy) 3] 2+. All evidences from the optimized structures, the calculated atomic charges and spin densities for the triplet complexes support the conclusion that phosphorescent emission in the divalent Os and Ru complexes originate from the triplet metal-to-ligand-charge-transfer state. This has been discussed in detail.

A Europium(II) Complex with Benzo‐15‐Crown‐5

The present paper reports the crystal structure and luminescent properties of bis(benzo-15-crown-5)europium(II) diperchlorate. The structure is composed of complex bis(benzo-15-crown-5)europium(II) cations and perchlorate anions. The complex cation is centrosymmetric, and the metal ion is surrounded by 10 oxygen atoms of two ligand molecules. The compound shows very bright luminescence at 23450 cm−1. The emission parameters (wavelength and the average lifetime of the excited state) are compared to those previously reported for the analogous complex in methanol solutions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Copper complexes of a new tridentate imidazole-containing ligand: spectroscopy, structures and nitrite reductase reactivity: The molecular structures of [Cu(biap)(NO 2) 2] and [Cu(biap)Br 2

The ligand N, N-bis(2-ethyl-5-methyl-imidazol-4-ylmethyl)-aminopropane (abbreviated as biap) forms several copper(II) coordination compounds with general formula [Cu(biap)X 2], with X −=Cl −, Br −, NO 3 − , NO 2 − and NCS −. In all these compounds the ligand biap acts as a tridentate ligand. Single crystals of [Cu(biap)(NO 2) 2] and [Cu(biap)Br 2] were used for X-ray structure determinations. All compounds were characterized by IR, ligand field and EPR spectroscopy, and cyclic voltammetry. The geometry of copper(II) in the (pseudo-) halide complexes is five-coordinate, whereas copper(II) is distorted octahedrally coordinated in the nitrate and nitrite complexes, whereby one of the anions binds didentate chelating and the other one monodentate. The affinity of nitrite for the [Cu(biap)] 2+ cation was studied by determining the binding constant of the anion to the perchlorate salt of the complex in methanol solution. The data show that nitrite exhibits high affinity for the complex and its behavior is comparable with that of azide. The reduction of nitrite, to produce nitric oxide, by the reduced complex [Cu(biap)] + has been studied anaerobically. Kinetic experiments showed that the reaction exhibits saturation behavior with respect to nitrite concentration. The kinetic data indicate that [Cu(biap)] + has a moderate efficiency in the nitrite reductase reaction.

Fluorescence study of some terbium–oligopeptide complexes in methanolic solution

This study concerned the use of lanthanide chelates to detect glycyl-leucyl-phenylalanine (GLF) and its homologues. Spectroscopic analysis of peptides without or with terbium complexation revealed the formation of (LF) 3(Tb) 2, (GF) 3(Tb) 2, (GLF) 3(Tb) 2 and (FL) 4Tb, (FG) 4Tb complexes with high stability constants in methanolic solutions (p K d>13). Lanthanide chelate emission displayed a large Stokes shift (>270 nm), which allowed Tb chelates of GLF and its derivatives to be used for detection purposes. However, this preliminary study indicated some important limitations associated with lanthanide chelation, such as high methanolic content.

Mechanism of Br 2·− and Cl 2·− radical anions formation upon IrCl 62− photoreduction in methanol solutions containing free Br − and Cl − ions

Laser flash photolysis has been used to study the formation of X 2 ·− radical ions (X = Br and Cl) upon photoreduction of IrCl 6 2− complex in methanol solutions, containing free X − ions. It has been shown that two channels of halogen atom formation are possible. These are the reactions Of X − ions with either the primary radical cation CH 3OH ·+ which results from single electron transfer from a methanol molecule to the excited complex or the intermediate, arising from transformation of primary light-excited IrCl 6 2− complex.

Nuclear magnetic resonance study of the ligand interchange of Ba2+-18-crown-6 complex in methanol solution

Exchange kinetics of Ba2+-18-crown-6 complex in deuterated methanol solution was studied by proton NMR line-shape analysis of a series of solutions containing equal population of free and complexed 18-crown-6, but varying concentration of the macrocycle, at various temperatures. From −33 to 37°C, the predominant mechanism for the exchange of the ligand between the two sites is a bimolecular pathway which is characterized by the following activation parameters:Ea=47±2 kJ-mol−1; ΔH≠=45±2 kJ-mol−1; ΔS≠=−8±4 J-mol−1-K−1. However, the contribution of a dissociative mechanism with activation parametersEa=36±5 kJ-mol−1, ΔH≠=33±5 kJ-mol−1 and ΔS≠=104±18 J-mol−1-K−1 becomes more important at higher temperatures.

Photochemistry of the PtCl 62− complex in methanol solution

In the laser flash photolysis of PtCl 6 2− in methanol, a non-linear dependence of the yields of the trivalent platinum intermediates PtCl 6 3− and PtCl 5 2− on laser pulse intensity is observed. The non-linearity is due to the absorption of photons by PtCl 6 3− which is a primary product resulting from the electron transfer from a methanol molecule to excited PtCl 6 2−. Photodissociation of PtCl 6 3− yields PtCl 5 2−. However, PtCl 6 3− in the ground state also dissociates into PtCl 5 2− and Cl −. This monomolecular process proceeds with an activation energy of 29.7 kJ mol −1 and a rate constant of 1.05 × 10 6 s −1 at 300 K. The parameters of the reverse reaction between Cl − and PtCl 5 2− which yields PtCl 6 3− have also been measured (activation energy, −9.6 kJ mol −1; rate constant at 300 K, 7.6 × 10 6 M −1 s −1). When free Cl − is present in methanol at a concentration of more than 0.1 – 0.2 M, electron transfer from Cl − to excited PtCl 6 2− is also possible. The chlorine atom formed reacts with Cl − yielding the radical ion Cl 2 − which is detected by an intense absorption band with a maximum at 340 nm.

Amino acids as CH-acids 17. Increase in the amino acid ?-proton mobility in Schiff base copper complexes with pyridine or N-2-pyridinecarbonyl-2?-aminobenzaldehyde ligands

1. The reversible replacement of methanol by methylate ion in the equatorial plane of the copper complex of N-salicylidene-S-valine has been studied spectrophotometrically; study has also been made of the kinetics of the MeO− ion-catalyzed racemization of the S-valine fragment of this complex in methanol solution at 25°C. 2. Pyridine and N-salicylidene-S-valine form a mixed complex with copper ions, the kinetic CH-acidity of this complex being higher than that of copper N-salicylidene-S-valinate. 3. N-2-Pyridinecarbonyl-2-aminobenzaldehyde has been synthesized and its Schiff base with S-valine used as ligand in a copper complex. Under the action of MeO−, the S-valine fragment of this complex racemizes 90 times more rapidly than the S-valine fragment of copper N-salicylidene-S-valinate.

To enzyme analogues by lock and key chemistry with crown compounds. Part 1. Enantiomeric differentiation by configurationally chiral cryptands synthesised from L-tartaric acid and D-mannitol.

The requirements of an enzyme analogue are discussed in terms of (i) binding, (ii) chirality, and (iii) functionality. The ability of 18-crown-6 derivatives to complex with primary alkylammonium cations indicates the potential of the 18-crown-6 constitution to provide the binding requirement of an enzyme analogue. Attention is drawn to the fact that carbohydrates provide not only functionality but also a relatively inexpensive source of chiral bismethylenedioxy units for incorporation into the 18-crown-6 framework. The optically pure configurationally chiral cryptands L-(14), LL-(15), LL-(16), LL-(17), DD-(17), LL-(18), DD-(28), D-(29), DDD-(30), DD-(31), DD-(32), and DD-(33) have been synthesised from L-tartaric acid and D-mannitol. The 18-crown-6 locks excluding the tetraol LL-(16) and the octaol DD-(31), have been shown by 1H n.m.r. spectroscopy to form complexes in CD2Cl2 with primary alkylammonium salts. The stability constants for complexes formed in CDCl3 solution between (i) t-butylammonium thiocyanate and (ii) benzylammonium thiocyanate and some of these 18-crown-6 locks have been determined by an 1H n.m.r. spectroscopic method and compared with the complexing ability of 18-crown-6 (34). 1H and 13C N.m.r. spectroscopy has been used to demonstrate that the locks LL-(18) and DD-(28) exhibit enantiomeric differentiation in complexation equilibria towards (RS)-α-phenylethylammonium hexafluorophosphate [(RS)-(8),HPF6]. The tetraol LL-(16) and the octaol DD-(31) have been shown by 1H n.m.r. spectroscopy to form complexes in CD3OD and D2O with primary alkylammonium salts. The tetra-O-isopropylidene derivative DD-(28) forms strong complexes in methanolic solution with alkali metal cations.

Evidence for a chelated lithium bisacetylacetonate (Li(acac) 2−) complex in methanol solution

Evidence for a chelated lithium bisacetylacetonate (Li(acac) 2−) complex in methanol solution