Fourier-transform NMR Research Articles

Molecular engineering and modification of FCC slurry oil residue for improving ageing resistance of high quality paving asphalt

In the present work, a novel resin molecule based on fluid catalytic cracking (FCC) slurry oil residue was designed and prepared with aid of molecular simulation to improve its ageing resistance. The average molecular structure of resin was characterized with elemental analysis, Fourier-transform IR (FT-IR) spectroscopy, NMR spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and designed resin was synthesized by attaching an additional propyl group to the as-received resin. The interactions of resins and asphaltene molecules were investigated via molecular simulation, UV-visible (UV-Vis) spectroscopy and atomic force microscopy (AFM). The results revealed that the equilibrium distance of designed resin-asphaltene dimer decreased from 0.42 nm to 0.38 nm while the lowest contact energy increased from 9.3 kcal/mol to 11.2 kcal/mol, indicating an improved stability of designed resin-asphaltene particles. The adsorption isotherm indicated that more modified resin molecules could be adsorbed by asphaltene than the original resin. Compared with original asphalt, less aggregation of asphaltene occurred in asphalt blended with modified slurry oil residue during ageing process, showing its greatly improved ageing resistance.

Novel Water-Soluble Cyclotriphosphazene-Bodipy Conjugates: Synthesis, Characterization and Photophysical Properties

In the present work, novel water-soluble cyclotriphosphazene derivatives (3b and 4b) were synthesized by 'click' reactions between cyclotriphosphazene derivative with hydrophilic glycol side groups (2) and Bodipy's (3a and 4a). All newly synthesized compounds (2, 3b and 4b) were characterized by fourier-transform infrared (FTIR), mass and NMR spectroscopy techniques and elemental analysis (EA). The photophysical properties of Bodipy substituted novel cyclotriphosphazenes (3a and 4a) were examined via UV-Vis absorption and fluorescence emission spectroscopy inside water and many organic solvents such as acetone, tetrahydrofuran, dichloromethane, dimethyl sulfoxide, etc., and the results were compared with the each other. Graphical Abstract.

T2* weighted Deconvolution of NMR Spectra: Application to 2D Homonuclear MAS Solid-State NMR of Membrane Proteins

2D homonuclear NMR spectroscopy is an essential technique to characterize small and large molecules, such as organic compounds, metabolites, and biomacromolecules at atomic resolution. However, for complex samples 2D homonuclear spectra display poor resolution, making spectral assignment very cumbersome. Here, we propose a new method that exploits the differential T2* relaxation times of individual resonances and resolves the 2D NMR peaks into pseudo-3D spectra, where time is the 3rd dimension. T2* weIghted DEconvolution or TIDE analyzes individual free induction decays (FIDs) and dissects them into sub-FIDs that are transformed into pseudo-3D spectra combining Fourier transformation and covariance NMR. TIDE achieves higher resolution and sensitivity for NMR spectra than classical covariance NMR reducing offset-dependent artifacts. We demonstrate the performance of TIDE for magic angle spinning (MAS) [13C,13C]-DARR NMR spectra of single- and multi-span membrane proteins embedded in lipid bilayers. Since TIDE is applicable to all type of homonuclear correlation experiments for liquid and solid samples, we anticipate that it will be a general method for processing NMR data of biomacromolecules, complex mixtures of metabolites as well as material samples.

Spectrokinetic Studies of the Products of Conversion of Natural Phenols in Radical Reactions

Fourier-transform IR and NMR spectroscopy are used to show that, in the reaction with 2,2'‑diphenyl-1-picrylhydrazyl radical, the secondary products of natural phenol conversion are dimeric compounds formed by recombination of phenoxyl radicals. According to thermodynamic parameters of the reaction calculated by the DFT method the most stable structures in the studied system are CC dimers. The resulting dimeric phenols show a lowered antiradical activity compared to the original phenol, which ensures a prolonged effect of the original antioxidant and enhances its overall antioxidant activity in radical oxidation reactions.

Facile access to polymer supported zinc–salen complex: highly efficient heterogeneous catalyst for synthesizing hydantoins, thiohydantoins and Schiff bases in aqueous medium

The synthesis of polymer supported zinc–salen complex (PS-Zn–salen) is described. The mononuclear zinc(II)–salen complex was characterized by Fourier-transform NMR spectroscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrophotometry (FT-IR), thermogravimetric analysis, scanning electron microscopy, surface area and pore size distribution by Brunauer–Emmett–Teller. The synthesized PS-Zn–salen complex used as a recyclable heterogeneous catalyst for the efficient synthesis of hydantoins, thiohydantoins and Schiff bases in an aqueous medium. The isolated yields of hydantoins, thiohydantoins and Schiff bases achieved up to 89, 95 and 94%, respectively. In spite of conventional heterogeneous catalysts, current PS-Zn–salen complex shows thermal stability up to 280 °C. Moreover, the catalyst could be recovered easily by simple filtration and reused for next run with slightly declining its activity up to six successive runs. The FT-IR spectrum of recycle catalyst after 6th run confirmed that the catalyst was stable during the course of a reaction. The leaching of metal from the PS-Zn–salen is negligible, which was confirmed by AAS and hot filtration test.

A highly recoverable polymer-supported ionic salen-palladium complex as a catalyst for the Suzuki-Miyaura cross coupling in neat water

A polymer supported Pd-salen complex (PS-Pd-salen) was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), Fourier-transform NMR spectroscopy (FT-NMR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), surface area and pore size distribution by Brunauer-Emmett-Teller (BET). The heterogeneous catalytic performance of the PS-Pd-salen for the Suzuki-Miyaura coupling of variety of phenyl boronic acid with different aryl halides was successfully conducted in water with K2CO3 and 20 mg catalyst loading at room temperature. The coupling reactions with aryl iodides and bromides were achieved at room temperature with good to excellent yield; whereas the reactions with aryl chlorides were performed in aqueous-ethanol (1:1) at 90 °C. The product yields related with the substrates were optimized, and main reaction factors influencing the yields were also recognized. The results clearly indicated that the reaction constraints needed to achieve high yields are substrate-reliant. The hot filtration test verified heterogeneous nature of PS-Pd-salen complex. Moreover, the catalyst showed excellent reusability for five successive runs in slight compromising with its activity.

Nucleophilic substitution reactions of [(η5-Cp*)Ru(η6-C6H5CO2H)]+: Synthesis, characterization and cytotoxicity of organoruthenium ester and amide complexes

This article outlines the synthesis of an electrophilic organoruthenium carboxylic acid of the structure [(η5-Cp*)Ru(η6-C6H5CO2H)]+ and explores the behavior of this molecule under a variety of nucleophilic substitution conditions using a range of oxygen and nitrogen based nucleophiles including alcohols, primary and secondary amines and aromatic sulfonamides. The resulting organoruthenium ester [(η5-Cp*)Ru(η6-C6H5COOR)]+ and amide [(η5-Cp*)Ru(η6-C6H5CONHR)]+ or [(η5-Cp*)Ru(η6-C6H5CONR)]+ complexes are additionally reported. All prepared complexes have been fully characterized using Fourier-transform IR and NMR spectroscopy and electrospray mass spectrometry with single-crystal X-ray structural determinations reported for three complexes: 3[(η5-Cp*)Ru(η6-C6H5CO2H)]B(C6H5)4.[(η5-Cp*)Ru(η6-C6H5CO2)].H2O, [(η5-Cp*)Ru(η6-C6H5CONHCH2Ph)]PF6 and [(η5-Cp*)Ru(η6-C6H5CONHSO2C6H4COMe)]PF6. Complexes were also evaluated for in vitro cytotoxic activity against the MCF7 (hormone-dependant breast cancer), MDA-MD-231 (hormone-independent breast cancer), MM96L (human melanoma) tumourigenic cell lines and the normal NFF (neonatal foreskin fibroblasts) human cell line.

Design of aqueous two-phase systems for purification of hyaluronic acid produced by metabolically engineered Lactococcus lactis.

Hyaluronic acid has a wide range of biomedical applications and its commercial value is highly dependent on its purity and molecular weight. This study highlights the utility of aqueous two-phase separation as a primary recovery step for hyaluronic acid and for removal of major protein impurities from fermentation broths. Metabolically engineered cultures of a lactate dehydrogenase mutant strain of Lactococcus lactis (L. lactis NZ9020) were used to produce high-molecular-weight hyaluronic acid. The cell-free fermentation broth was partially purified using a polyethylene glycol/potassium phosphate system, resulting in nearly 100% recovery of hyaluronic acid in the salt-rich bottom phase in all the aqueous two-phase separation experiments. These experiments were optimized for maximum removal of protein impurities in the polyethylene glycol rich top phase. The removal of protein impurities resulted in substantial reduction of membrane fouling in the subsequent diafiltration process, carried out with a 300 kDa polyether sulfone membrane. This step resulted in considerable purification of hyaluronic acid, without any loss in recovery and molecular weight. Diafiltration was followed by an adsorption step to remove minor impurities and achieve nearly 100% purity. The final hyaluronic acid product was characterized by Fourier-transform IR and NMR spectroscopy, confirming its purity.

Dipeptide Structural Analysis Using Two-Dimensional NMR for the Undergraduate Advanced Laboratory

A laboratory experiment was developed to introduce students in either an organic chemistry or biochemistry lab course to two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy using simple biomolecules. The goal of this experiment is for students to understand and interpret the information provided by a 2D NMR spectrum. Students are provided three unknown samples: a dipeptide and each of the two amino acids that make up the dipeptide. A Fourier transform-NMR (60 MHz) instrument is used to record standard proton (1H) NMR spectra for each of the unknown samples. By interpreting the 1H NMR spectra for the two single amino acid unknown samples, students identify the amino acids in the dipeptide. For the dipeptide molecule, students record the 1H and correlation spectroscopy (COSY or 1H–1H) NMR spectra. The students use the COSY spectrum information to assign all of the proton peaks in the more complicated 1D 1H spectrum of the dipeptide. A comparative analysis of the NMR spectra for dipeptides with the same amino acid constituents reveals that the order in which the amino acids are connected in the dipeptide influences the chemical shift of at least the α-protons.

Multidimensional Approaches to NMR-Based Metabolomics

Multidimensional Approaches to NMR-Based Metabolomics

Analysis of Nutation Patterns in Fourier-Transform NMR of Non-Thermally Polarized Multispin Systems

AbstractThe complex spin order of hyperpolarized multispin systems giving rise to anomalous NMR spectral patterns that vary with the RF excitation angle is analyzed by decomposing its nutation behavior in a superposition of Fourier harmonics. The product operator formalism is applied to calculating the spectral contributions of the various mutual alignments of scalar coupled spins. Two cases are treated, namely systems exhibiting only differences in population of their spin states and systems showing in addition zero-quantum coherences between states, a situation often seen at hyperpolarization. After deriving the general solution a number of representative examples are discussed in detail. The theoretical treatment is applied to analyzing the spin order observed in a hyperpolarized two-spin system that is prepared in the singlet state by para-hydrogen induced polarization.

ChemInform Abstract: Data Sampling in Multidimensional NMR: Fundamentals and Strategies

AbstractReview: 46 refs.

Selective, Cytotoxic Organoruthenium(II) Full‐Sandwich Complexes: A Structural, Computational and In Vitro Biological Study

A structurally diverse range of lipophilic, cationic η(6)-arene η(5)-cyclopentadienyl (η(5)-Cp*) full-sandwich complexes of ruthenium(II) have been prepared and structurally characterized by Fourier-transform IR and NMR spectroscopy, electrospray mass spectrometry, and elemental microanalyses. Computational experiments incorporating the Hartree-Fock theory and the second-order Møller-Plesset perturbation theory predict each complex to possess a uniform δ+ electrostatic potential, with the cationic charge of the [RuCp*](+) moiety completely delocalizing throughout the molecular structure of each metallocene. In vitro cytotoxicity studies demonstrate these delocalized lipophilic cations to be potent growth inhibitors of eleven unique tumorigenic cell lines, while exhibiting significantly lower levels of toxicity towards both a normal human fibroblast and a mouse macrophage cell line. Single-crystal X-ray structural determinations are additionally reported for five complexes, [Ru(η(6)-C(6)H(5)(CH(2))(2)CH(3))(η(5)-C(5)(CH(3))(5))]BPh(4), [Ru(η(6)-C(6)H(5)CO(2)CH(2)CH(3))(η(5)-C(5)(CH(3))(5))]BF(4), [Ru(η(6)-C(10)H(8))(η(5)-(5) (CH(3))(5))]BPh(4), [Ru(η(6)-C(14)H(10))(η(5)-C(5)(CH(3))(5))]BPh(4), and [Ru(η(6)-C(16)H(10))(η(5)-C(5)(CH(3))(5))]BPh(4).

Utilization of green seed canola oil for in situ epoxidation

Green seed canola oil is underutilized for edible purposes due to its high chlorophyll content, which makes it more susceptible to photo-oxidation and ultimately reduces the oxidation stability. The present work is an attempt to compare the kinetics of epoxidation of crude green seed canola oil (CGSCO) and treated green seed canola oil (TGSCO) with peroxyacids generated in situ in presence of an Amberlite IR-120 acidic ion exchange resin (AIER) as catalyst. Among the two oxygen carrier studied, acetic acid was found to be a better carrier than the formic acid, as it gives 8% more conversion of double bond than the formic acid. A detailed process developmental study was then performed with the acetic acid/AIER combination. For the oils under investigation parameters optimized were temperature (55°C), hydrogen peroxide to double bond molar ratio (2.0), acetic acid to double bond molar ratio (0.5), and AIER loading (15%). An iodine conversion of 90.33, 90.20%, and a relative epoxide yield of 90, 88.8% were obtained at the optimum reaction conditions for CGSCO and TGSCO, respectively. The formation of the epoxide product of CGSCO and TGSCO was confirmed by Fourier Transform IR Spectroscopy (FTIR) and NMR (1H NMR) spectral analysis.

Novel Hydroxy- and Methyl-Terminated Triaromatic Schiff Base Compounds: Synthesis and Mesogenic Properties

A series of Schiff base hydroxy-mesogens and their model compounds have been synthesized. The mesogen is constructed from three-ring-containing mesogens linked through ester and azomethine groups with a terminal hydroxy group. The related model compounds were also synthesized with varying chain length with a terminal methyl group and their properties were compared with that of hydroxy mesogens. Extensive characterization of all mesogenic compounds was carried out by Fourier-transform IR, 1H and 13C NMR and mass spectroscopy. The phase characteristics such as nature of phase, melting and clearing temperatures and phase range were evaluated using a hot-stage optical polarizing microscope and differential scanning calorimetry. The appearance of enantiotropic smectic phases is due to the high molecular polarizability of the triaromatic core with azomethine and ester linkages.

Synthesis, Structure, and Selective Cytotoxicity of Organometallic Cp*RuII O-Alkyl-N-phenylcarbamate Sandwich Complexes

Tetraphenylborate salts of the η6-arene Cp*RuII O-alkyl-N-phenyl carbamate organometallic sandwich complexes, [Cp*Ru(PhNHCO2R)]BPh4 for R = Me (1), Et (2), and n-Pr (3), have been prepared by a facile one-pot reaction between ruthenium trichloride, pentamethylcyclopentadiene, and phenylisocyanate in refluxing alcohol solutions, and have been characterized by Fourier-transform IR and NMR spectroscopy, electrospray mass spectrometry, and single-crystal X-ray structure determinations. In vitro cytotoxicity studies show the complexes to be potent growth inhibitors for a range of tumour cell lines, while expressing significantly lower levels of toxicity towards a normal human fibroblast cell line.

Synthesis and Properties of Novel 'Ethyne-linked' Compounds Containing Carbazole and 1, 8-naphthalimide Groups

A series of the novel ‘ethyne-linked’ compounds containing carbazole and 1,8-naphthalimide groups have been synthesized by Pd/Cu-catalyzed Sonogashira reaction. These compounds were fully characterized by means of Fourier-transform IR, 1H, 13C NMR, and high resolution mass spectroscopy. The thermal, optical, and electrochemical properties were also investigated. As we expected, the results indicated that these compounds could improve charge-transport ability and fluorescent quantum yield by introducing the electron-transporting emitting moieties naphthalimide and the alkyne group to carbazole moieties.

Spatial encoding strategies for ultrafast multidimensional nuclear magnetic resonance

Multidimensional spectroscopy plays a central role in contemporary magnetic resonance. A general feature of multidimensional NMR is its inherent multiscan nature, stemming from the methodology's reliance on a series of independent acquisitions to sample the spins' evolutions throughout the indirect time domains. Contrasting this traditional feature, an acquisition scheme has recently been reported that enables the collection of complete of multidimensional NMR data sets within one single scan. Provided that the signals to be observed are sufficiently strong, this new "ultrafast" protocol can thus shorten the acquisition times of multidimensional NMR experiments by several orders of magnitude. This new methodology operates by departing from temporal encoding principles used since the advent of Fourier-transform NMR, replacing them with a spatial encoding of the spin interactions. Spatial encoding operates in turn on the basis of novel radiofrequency irradiation and magnetic field gradient waveform manipulations, designed so as to impart on the sample a coherent spin magnetization pattern that reflects the internal interactions to be measured. Given the central role played by this new kind of spectroscopic-oriented manipulations in ultrafast NMR, we devote this review to surveying different variants that have hitherto been proposed for their implementation. These include both discrete and continuous versions, real- and constant-time implementations, as well as amplitude- and phase-modulated alternatives. The principles underlying these various spatial encoding approaches are treated, their operation is graphically illustrated as well as formally derived within suitable theoretical frameworks, and an in-depth comparison of their line shape characteristics is discussed.

Synthesis and Characterization of Some Metal Complexes of 4,5-Diazafluoren-9-one and their Biological Effects on Human Carcinoma Cells

Three new transition metal complexes of 4,5-diazafluoren-9-one, [(DAFO)PdCl2], [(DAFO)PtCl2], and [(DAFO)ZnCl2], were prepared in good yields by the reactions between appropriate metal chloride precursors and 4,5-diazafluoren-9-one under ambient conditions. The structures of these metal complexes were established by spectroscopic (Fourier-transform IR, NMR, and fast-atom bombardment mass spectrometry) techniques. The possible biological activity of these compounds on three human cancer cell lines including Hep3B, MDAMB-231, and SKHep-1 was investigated. The results obtained showed that both zinc- and platinum-containing compounds exhibit a similar growth inhibitory effect on these three cancer cell lines when compared with the prototypical cis-platin. In contrast, the corresponding palladium congener is virtually biologically inactive in these trials.

Using an NMR Spectrometer To Do Magnetic Resonance Imaging

A conventional Fourier-transform NMR spectrometer with a triple-axis gradient probe can function as a MRI imager. In this experiment students gain hands-on experience with MRI while they learn about important principles underlying the practice of NMR, such as gradients, multi-dimensional spectroscopy, and relaxation. Students image a biological specimen that fits in a 5-mm NMR tube with the multi-slice-multi-echo (MSME) method and measure the transverse relaxation time, T2, of water in selected regions of interest.