Range Of Solvent Systems Research Articles

Coordination chemistry of Be2+ ions with chelating oxygen donor ligands: further insights using electrospray mass spectrometry

Abstract The electrospray ionisation mass spectrometric (ESI-MS) behaviour of various complexes of beryllium have been investigated in the work described in this paper. These beryllium complexes were analysed in situ on a small scale by preparing appropriate molar mixtures of the Be2+ ion with ligands in a range of solvent systems. In view of the toxicity of beryllium compounds, this combinatorial type screening, involving miniscule amounts of material in solution, proved to be a safe strategy to pursue the coordination chemistry of beryllium. A variety of beryllium complexes were generated with various ligands in solutions and subjected to detailed characterisation by ESI-MS. These ligands, containing functional groups or architecture of interest, varied from simple ligands such as the acetate ion to more common beryllium chelators including hydroxy keto ligands (maltol, tropolone), malonic acid, chromotropic acid and citric acid. Generally, there was excellent correlation between the species observed in the mass spectrum and those confirmed to exist in solution by other techniques. This lent strong credence to the ESI-MS methodology used as an efficient analytical technique for the easy screening of a diverse range of potential ligands for the divalent beryllium ion.

Redox Exfoliation of Layered Transition Metal Dichalcogenides.

Transition metal dichalcogenides (TMDs) have attracted considerable attention in a diverse array of applications due to the breadth of possible property suites relative to other low-dimensional nanomaterials (e.g., graphene, aluminosilicates). Here, we demonstrate an alternative methodology for the exfoliation of bulk crystallites of group V-VII layered TMDs under quiescent, benchtop conditions using mild redox chemistry. Anionic polyoxometalate species generated from edge sites adsorb to the TMD surface and create Coulombic repulsion that drives layer separation without the use of shear forces. This method is generalizable (MS2, MSe2, and MTe2) and effective in preparing high-concentration (>1 mg/mL) dispersions with narrow layer thickness distributions more rapidly and with safer reagents than alternative solution-based approaches. Finally, exfoliation of these TMDs is demonstrated in a range of solvent systems that were previously inaccessible due to large surface energy differences. These characteristics could be beneficial in the preparation of high-quality films and monoliths.

Low temperature synthesis study of metal-organic framework CPO-27: investigating metal, solvent and base effects down to -78 °C.

CPO-27-M (M = Co, Mg, Ni, Zn) metal-organic frameworks have been successfully synthesized at temperatures down to -78 °C in a range of solvent systems and their crystallinity and morphology analyzed by powder X-ray diffraction and scanning electron microscopy. CPO-27-Mg and -Zn could be synthesized at lower temperatures using MeOH-NaOH as the solvent with CPO-27-Zn showing the most crystalline material at -78 °C. CPO-27-Zn afforded the most crystalline samples of all studies in MeOH-TEA. However, in MeOH a non-porous monomeric [Zn(H2dhtp)(H2O)2] complex was formed when no base was present. In THF with base (NaOH, TEA) the reaction produced crystalline MOFs in a controlled and stable manner at low temperatures, whilst the reagents were insoluble in THF at low temperature when no base was present. SEM was used to analyze the morphologies of the products.

Thermodynamics of Self‐Assembly of Dicarboxylate Ions with Binuclear Lanthanide Complexes

Self-assembly of a range of carboxylic acids (benzoic acid, dinicotinic acid, nicotinic acid, and isophthalic acid) with the europium complex of 5-nitro-α,α′-bis(DO3Ayl)-m-xylene (where DO3A is 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) has been explored to establish the thermodynamics of binding in a range of solvent systems and in a range of aqueous buffer solutions. In this system, profound effects are observed as a consequence of competition by the hydroxide ion, which outcompetes even dinicotinate at high pH. In the case of isophthalate, which binds most strongly, and dinicotinate, both enthalpic and entropic contributions to binding have been identified. The europium complex with 5-nitro-α,α′-bis(DO3Ayl)-m-xylene is found to have a solution structure significantly different from the related europium complex of 5-amino-α,α′-bis(DO3Ayl)-m-xylene. It is found that phosphate binds strongly to the europium complex of the nitro derivate but not to the europium complex of amino derivative. Lactate, citrate, and pyruvate also bind strongly to 5-nitro-α,α′-bis(Eu⋅DO3Ayl)-m-xylene, and it is concluded that the solution structure of this binuclear lanthanide complex is significantly different from that of the amino-substituted complex.

Establishing trends based on solvent system changes in cocrystals containing pyrogallol[4]arenes and fluorescent probes rhodamine B and pyronin Y

Eight cocrystal structures containing a pyrogallol[4]arene of varying aliphatic tail lengths and either fluorescent probes rhodamine B or pyronin Y in a range of solvent systems are examined. Trends based on probe, solvent, and aliphatic tail length are investigated.

Fabricating High Performance, Donor–Acceptor Copolymer Solar Cells by Spray‐Coating in Air

AbstractWe report the fabrication of high performance organic solar cells by spray‐coating the photoactive layer in air. The photovoltaic blends consist of a blend of carbazole and benzothiadiazole based donor–acceptor copolymers and the fullerene derivative PC70BM. Here, we formulate a number of photovoltaic inks using a range of solvent systems that we show can all be deposited by spray casting. We use a range of techniques to characterize the structure of such films, and show that spray‐cast films have comparable surface roughness to spin‐cast films and that vertical stratification that occurs during film drying reduces the concentration of PCBM towards the underlying PEDOT:PSS interface. We also show that the active layer thickness and the drying kinetics can be tuned through control of the substrate temperature. High power conversion efficiencies of 4.3%, 4.5% and 4.6% were obtained for solar cells made from a blend of PC70BM with the carbazole‐based co‐polymers PCDTBT, P2 and P1. By applying a low temperature anneal after the deposition of the cathode, the efficiency of spray‐cast solar‐cells based on a P2:PC70BM blend is increased to 5.0%. Spray coating holds significant promise as a technique capable of fabricating large‐area, high performance organic solar cells in air.

Separation of Delphinidin-3-O-sambubioside, Cyanidin-3-O-sambubioside and p-Coumaric Acid from Cranberry by CCC Followed by prep-HPLC Using Robotic CCC Solvent System Selection

High-performance counter-current chromatography has been used for the separation of delphinidin-3-O-sambubioside, cyanidin-3-O-sambubioside and p-coumaric acid from crude extract of cranberry. The separation was performed with a two-phase solvent system composed of butanol/0.05% aqueous trifluoroacetic acid/methanol at a volume ratio of 4:5:1. The two-phase solvent system was selected following the determination of partition coefficients (K) in a range of solvent systems using a robotic solvent system selection method. Analytical scale CCC confirmed that this phase system separated the components from a crude cranberry extract (40 mg scale) with acceptable purities. Preparative CCC of 400 mg of crude yielded 4.2 mg of p-coumaric acid at a purity of over 98%, 3.6 mg of delphinidin-3-O-sambubioside at a purity of over 97% and 4.5 mg of cyanidin-3-O-sambubioside at a purity of 73%, which was further purified by preparative high-performance liquid chromatography to yield 3 mg cyanidin-3-O-sambubioside at 95% purity. The identification of delphinidin-3-O-sambubioside, cyanidin-3-O-sambubioside and p-coumaric acid was performed by ESI-MS, 1H-NMR and 13C-NMR spectra.

ChemInform Abstract: Model Solvent Systems for QSAR. Part 3. An LSER Analysis of the “ Critical Quartet”. New Light on Hydrogen Bond Strength and Directionality.

An LSER analysis of log P for the ‘critical quartet’ of solvent systems has been carried out using, as initial variables, VI for volume, µ2 for dipolarity, and proton donor ∑α and proton acceptor βf scales based on log Kα and log Kβ respectively. A common data matrix and an unprecedented range of functionalities have been employed. By making the analysis stepwise, starting with the simplest solutes and adding more in order of increasing complexity, we have been able to identify hitherto unrecognised variables and ‘fine-tune’ established ones in such a way as to derive self-consistent proton donor and acceptor values applicable to the whole range of solvent systems. By this ‘LSER in reverse’ we have established, inter alia, the following new facts: (a)βf possesses a constant effective zero whereas that for ∑α is solvent-sensitive; (b) a new term nβf is required for acceptor solutes with two or more available lone pairs; (c) when neither lone pair is available, the acceptor strength of carbonyl is sharply reduced; (d) a second term specific to NH2 is required for ∑α in alkane and chloroform; (e) there is mutual shielding of XH and one lone pair in structures such as CO2H and CONH2; (f) ureas and other structures with parallel NH functions are proton donors of exceptional strength; (g) the acceptor ability of dipolar bases (PO and SO) varies with the solvent system.Cooperativity in solute–solvent bonding exists but takes complex forms, and does not appear strong enough to account e.g. for the hydrogen bonding properties of bulk water and the alcohols, for which mass action appears a likelier explanation. We present evidence (see Appendix) that mass action will most probably explain certain well known anomalies in the apparent proton acceptor ability of water as revealed by partitioning studies.The present results throw new light on previously anomalous octanol–water log P values and can predict f-values for other solvent systems. Most importantly, they provide new information not only on the strength of hydrogen bonding for more than 60 functional groups, but also on its directionality: we are able to predict, with reasonable certainty, which XH groups and lone pairs are actually available for bonding. This information is applicable to water, other solvents, and by implication to the biophase, so should find direct and immediate use in rationalising and quantifying drug–receptor interactions.

A Simple Method for the Prevention of Non-Specific Adsorption by Nanocrystals onto Surfaces

In this work we introduce an efficient method for averting non-specific adsorption of various nanoparticles to typical oxide surfaces, such as glass, quartz, and sapphire, through the attachment of a fluorinated self-assembled monolayer (SAM) that minimizes the interactions between stabilized nanoparticles and these surfaces. This surface treatment is shown to be effective for a variety of nanoparticles in a range of solvent systems. As a result, monitoring and characterization of nanoparticles and their surface chemistry is allowed, while simultaneously preventing loss of expensive nanomaterials to the various surfaces inherent in laboratory apparatus.

THE RELATIONSHIP BETWEEN RETENTION, LINEAR FLOW, AND DENSITY DIFFERENCE IN COUNTERCURRENT CHROMATOGRAPHY

Countercurrent Chromatography is a high-resolution, liquid-liquid chromatography process which is generic in nature and can be used with a wide range of solvent systems. This paper shows there are simple relationships between the operational variables affecting CCC, which lead to a clearer understanding of how the process works. In the future, it will be easier to predict phase system behaviour from the physical characteristics of the phase system and the operating conditions of the coil planet centrifuge and, so, simplify the process of getting started with a new phase system.

NMR studies of hydrogen bonding interactions with secondary amide and urea groups

AbstractThe cis/trans ratios for six model secondary amides were determined by 1H NMR in a range of solvent systems. The trans to cis equilibrium in chloroform is only slightly affected by addition of the hydrogen bond donor, trifluorethanol, but the cis rotamer is stabilized by an average of 0.7 kcal mol−1 when acetic acid is used as an intermolecular donor–acceptor template. Conversely, amide interaction with anionic hydrogen bond acceptors decreases the percentage of cis rotamer. 15N NMR spectroscopy was used to determine the effect of hydrogen bonding on the trans amide structure. The direction and the magnitude of 15N complex‐induced‐shifts indicate that both hydrogen bond donors and acceptors raise the secondary amide rotational barrier by increasing the CN bond order. The relationship of these results to protein structure is discussed. Copyright © 2001 John Wiley & Sons, Ltd.

Solvent and Matrix Combinations in the Quality of Matrix-assisted Laser Desorption/Ionization-Time of Flight Mass Spectra Obtained from Microorganisms

We have studied a number of commonly used matrices and a range of solvent systems, of widely varying polarity, used in matrix assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectra in an attempt to devise an optimum analytical strategy for the rapid characterization of pathogenic microorganisms. Several groups have recognized the usefulness of MALDI-TOF mass spectrometry in the characterization of these microorganisms, however, no consistent methodology has yet been developed which is in general use. Escherichia coli ATCC 9637 organisms were initially washed to remove growthmedium contaminants and then extracted with one of a range of solvents before admixing with either a single matrix ([2-(4-hydroxyphenylazo)]-benzoic acid, 2-mercaptobenzothiol, 2-amino-4-methyl-5-nitropyridine, or 2,6-dihydroxyacetophenone) or binary and ternary combinations of the four matrices. The results indicated that a binary combination of [2-(4-hydroxyphenylazo)]-benzoic acid and 2-mercaptobenzothiol (1:1) as matrix provides the most useful data with the organisms being extracted with 17% formic acid, 33% isopropyl alcohol and 50% water.

Model solvent systems for QSAR. Part 3. An LSER analysis of the ‘critical quartet.’ New light on hydrogen bond strength and directionality

An LSER analysis of log P for the ‘critical quartet’ of solvent systems has been carried out using, as initial variables, VI for volume, µ2 for dipolarity, and proton donor ∑α and proton acceptor βf scales based on log Kα and log Kβ respectively. A common data matrix and an unprecedented range of functionalities have been employed. By making the analysis stepwise, starting with the simplest solutes and adding more in order of increasing complexity, we have been able to identify hitherto unrecognised variables and ‘fine-tune’ established ones in such a way as to derive self-consistent proton donor and acceptor values applicable to the whole range of solvent systems. By this ‘LSER in reverse’ we have established, inter alia, the following new facts: (a)βf possesses a constant effective zero whereas that for ∑α is solvent-sensitive; (b) a new term nβf is required for acceptor solutes with two or more available lone pairs; (c) when neither lone pair is available, the acceptor strength of carbonyl is sharply reduced; (d) a second term specific to NH2 is required for ∑α in alkane and chloroform; (e) there is mutual shielding of XH and one lone pair in structures such as CO2H and CONH2; (f) ureas and other structures with parallel NH functions are proton donors of exceptional strength; (g) the acceptor ability of dipolar bases (PO and SO) varies with the solvent system.Cooperativity in solute–solvent bonding exists but takes complex forms, and does not appear strong enough to account e.g. for the hydrogen bonding properties of bulk water and the alcohols, for which mass action appears a likelier explanation. We present evidence (see Appendix) that mass action will most probably explain certain well known anomalies in the apparent proton acceptor ability of water as revealed by partitioning studies.The present results throw new light on previously anomalous octanol–water log P values and can predict f-values for other solvent systems. Most importantly, they provide new information not only on the strength of hydrogen bonding for more than 60 functional groups, but also on its directionality: we are able to predict, with reasonable certainty, which XH groups and lone pairs are actually available for bonding. This information is applicable to water, other solvents, and by implication to the biophase, so should find direct and immediate use in rationalising and quantifying drug–receptor interactions.

Photochemistry and photopolymerization activity of novel perester derivatives of fluorenone

The photochemistry and photopolymerization activity of three novel t-butylperester derivatives of fluorenone have been examined and compared with unsubstituted fluorenone and a tetra-t-butylperester of benzophenone. The longest wavelength absorption bands of all three derivatives are blue-shifted from that of fluorenone itself with a marked increase in the corresponding extinction coefficients, associated with the electron withdrawing effect of the peroxyester groups and a concurrent increase in the charge transfer content of the molecule due to substitution. The fluorescence quantum yields of the fluorenone derivatives are also greater than those of fluorenone in a range of solvent systems; this effect is associated with an increase in the degree of charge transfer content in the lowest excited singlet state. Photoreduction quantum yields are also higher in 2-propanol solvent, that for the bis-perester derivative being twice that of the monoperester. The presence of a tertiary amine (triethylamine) enhances the photoreduction quantum yields due to an increase in the probability of electron abstraction. Conventional micro-second flash photolysis in 2-propanol solution indicates that free radical formation occurs from an upper excited triplet n-π ∗ state. Rates of photopolymerization in bulk poly(methyl methacrylate) on a percentage basis are also higher for the three perester derivatives with those for the monoesters being greater than for the bisperester. The latter is associated with a much higher probability of self termination reactions. The presence of methyldiethanolamine enhances the rate of photopolymerization with both fluorenone and the monoperester derivatives but reduces that with the 2-t-butylperester, 7-nitro and bisperester derivatives due to competitive termination reactions. The results are discussed on the basis of the photophysical data and subsequent spectroscopic analysis of the polymer samples by second-order derivative u.v. spectroscopy and fluorescence analysis, both of which are shown to be valuable methods for the determination of chromophoric initiator fragments.

ChemInform Abstract: SOLUBILITY PROPERTIES IN POLYMERS AND BIOLOGICAL MEDIA. 2. THE CORRELATION AND PREDICTION OF THE SOLUBILITIES OF NONELECTROLYTES IN BIOLOGICAL TISSUES AND FLUIDS

Solubilities of a range of nonelectrolyte solutes in biological systems, such as blood, plasma, brain, lung, liver, kidney, muscle tissue, and human fat, are correlated and predicted through an equation that takes the form log Ltissue = c + w log Lwater + o log Loil, where L is the Ostwald solubility coefficient (or gas/liquid partition coefficient). The ratio of the constants o and w gives a measure of the oiliness of a given biological tissue or fluid. The strong possibility exists that, for many types of nonelectrolyte solutes, simple measurements of solubilities in water and oil (gas/liquid partition coefficients) will allow accurate predictions of solubilities in the above biological solvents, as well as tissue/blood partition coefficients. The solubility of rare gases and the inorganic gases H2, N2, CO, and O2 may be correlated through the simpler equation log Ltissue = l'RG + d', where l' and d' are constants that characterize the phase, and RG is a known parameter, obtained by normalizing and averaging solubilities over a range of solvent systems, that characterizes the solute. Both of the above equations allow prediction of L in biological solvents to within about 20%, which compares well with the precision of the experimental measurements.

Solubility properties in polymers and biological media. 2. The correlation and prediction of the solubilities of nonelectrolytes in biological tissues and fluids

Solubilities of a range of nonelectrolyte solutes in biological systems, such as blood, plasma, brain, lung, liver, kidney, muscle tissue, and human fat, are correlated and predicted through an equation that takes the form log Ltissue = c + w log Lwater + o log Loil, where L is the Ostwald solubility coefficient (or gas/liquid partition coefficient). The ratio of the constants o and w gives a measure of the "oiliness" of a given biological tissue or fluid. The strong possibility exists that, for many types of nonelectrolyte solutes, simple measurements of solubilities in water and oil (gas/liquid partition coefficients) will allow accurate predictions of solubilities in the above biological solvents, as well as tissue/blood partition coefficients. The solubility of rare gases and the inorganic gases H2, N2, CO, and O2 may be correlated through the simpler equation log Ltissue = l'RG + d', where l' and d' are constants that characterize the phase, and RG is a known parameter, obtained by normalizing and averaging solubilities over a range of solvent systems, that characterizes the solute. Both of the above equations allow prediction of L in biological solvents to within about 20%, which compares well with the precision of the experimental measurements.