Water Content In Acetonitrile Research Articles

Oxygen ether chain containing covalent organic frameworks as efficient fluorescence-enhanced probe for water detection

Three covalent organic frameworks (COFs) named as TPPA-DTM-COF, TPPA-BMTP-COF and TPPA-BETP-COF with different lengths of oxygen ether chains were successfully synthesized by the condensation between 4,4′,4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TPPA) with 2,5-dimethoxyterephthalaldehyde (DTM), 2,5-bis(2-methoxyethoxy)terephthalaldehyde (BMTP) and 2,5-bis(2-(2-methoxyethoxy)ethoxy)terephthalaldehyde (BETP), respectively, which have high crystallinity, large specific surface area and high thermochemical stability. The fluorescence performance of the as-prepared COFs in acetonitrile showed that the longer the oxygen ether chain, the stronger the fluorescence intensity, this may be related to the inhibition of aggregation-caused quenching (ACQ) effect with the increase of interlayer spacing. The resulting COFs also exhibited different emission in different solvents, and their fluorescence intensity has a significant and rapid response to water in organic solvents. Among them, TPPA-DTM-COF shows the most stable fluorescence emission and good dispersion in organic solvents. Its fluorescence intensity is linear with water content in acetonitrile ranging from 0% to 15% (V/V), and the detection limit was calculated to be 0.27%. In addition, the detection limits of COF in ethanol, THF and DMF are 0.15%, 0.43% and 0.39%, respectively. The mechanism of TPPA-DTM-COF detect water with fluorescence “on” may be that the water can form hydrogen bonds with N and O atoms on the skeleton of TPPA-DTM-COF, which enhanced the stability of the excited states of the COFs, thereby enhancing the intramolecular charge transfer (ICT) in the excitation state, leading to the enhancement of fluorescence. The superior properties of TPPA-DTM-COF inducing the as-prepared COF has a great prospect for trace amount water detection in organic solvents in the form of fluorescence enhancement.

Photoswitching of Diazocines in Aqueous Media.

We present a systematic investigation of the photophysical properties of diazocines in aqueous media. The Z-E photoconversion yields of CH2CH2- and CH2S-bridged diazocines decrease with increasing water content in acetonitrile. However, there is one exception. A CH2-NAc-bridged diazocine mostly retains its photostationary state in water (85 to 72%) because of the high quantum yields for the Z → E conversion. Moreover, it is water-soluble without further substitution and is therefore ideally suited as a photoswitch in biological (aqueous) environments.

The Colorimetric Signaling of Water Content by a Deprotonated Schiff Base in some Aprotic Organic Solvents

AbstractA simple Schiff base, (E)‐2‐[1‐{2‐(2,4‐dinitrophenyl)hydrazono}ethyl]phenol (Hdph) and its deprotonated form, (E)‐1‐(2,4‐dinitrophenyl)‐2‐{1‐(2‐hydroxyphenyl)ethylidene} hydrazine‐1‐ide (dph) have been synthesized and characterized by various physicochemical and spectroscopic techniques. Their structures have also been determined by single‐crystal X‐ray crystallography. The dph has been utilized as a colorimetric probe for the signaling of water content in some water‐miscible aprotic organic solvents (acetonitrile and tetrahydrofuran). The dph reveals a pronounced colorimetric behavior in response to the variation of water content in these solvents. Significant changes in UV‐visible absorption spectra permit a ratiometric analysis of the signaling behavior. The spectral changes are pronounced for the water content of less than 10 %, which is suitable for the application of dph as a receptor for the determination of water content in binary aqueous organic solvents having lower water content. The limit of detection (LOD) for water content in acetonitrile and tetrahydrofuran is calculated as 0.20 % and 0.28 %, respectively.

Uranyl tris nitrato as a luminescent probe for trace water detection in acetonitrile.

Uranyl tris nitrato i.e. [UO2 (NO3 )3 ]- was formed by adding tetramethylammonium nitrate to uranyl nitrate in acetonitrile medium. The luminescence features of this complex in acetonitrile are very sensitive to water content, which could lead to the use of it as a luminescent probe for water present in acetonitrile. The luminescence intensity ratio of 507 to 467nm peak of uranyl tris nitrato showed a linear response in the range 0-5% (v/v) water content in acetonitrile. The present method was applied for three synthetic samples of acetonitrile for water detection and the results obtained were compared using Karl Fischer titration. There was a good agreement in the values obtained by both the methods.

Lysozyme in water-acetonitrile mixtures: Preferential solvation at the inner edge of excess hydration.

Preferential solvation/hydration is an effective way for regulating the mechanism of the protein destabilization/stabilization. Organic solvent/water sorption and residual enzyme activity measurements were performed to monitor the preferential solvation/hydration of hen egg-white lysozyme at high and low water content in acetonitrile at 25 °C. The obtained results show that the protein destabilization/stabilization depends essentially on the initial hydration level of lysozyme and the water content in acetonitrile. There are three composition regimes for the dried lysozyme. At high water content, the lysozyme has a higher affinity for water than for acetonitrile. The residual enzyme activity values are close to 100%. At the intermediate water content, the dehydrated lysozyme has a higher affinity for acetonitrile than for water. A minimum on the residual enzyme activity curve was observed in this concentration range. At the lowest water content, the organic solvent molecules are preferentially excluded from the dried lysozyme, resulting in the preferential hydration. The residual catalytic activity is ∼80%, compared with that observed after incubation in pure water. Two distinct schemes are operative for the hydrated lysozyme. At high and intermediate water content, lysozyme is preferentially hydrated. However, in contrast to the dried protein, at the intermediate water content, the initially hydrated lysozyme has the increased preferential hydration parameters. At low water content, the preferential binding of the acetonitrile molecules to the initially hydrated lysozyme was detected. No residual enzyme activity was observed in the water-poor acetonitrile. Our data clearly show that the initial hydration level of the protein macromolecules is one of the key factors that govern the stability of the protein-water-organic solvent systems.

8(E)-4-[{2-(2,4-dinitrophenyl)hydrazono}benzene-1,3-diol] as a solvatochromic Schiff base and chromogenic signaling of water content by its deprotonated form in acetonitrile

A simple, cost effective Schiff base (E)-4-[{2-(2,4-dinitrophenyl)hydrazono}benzene-1,3-diol] (DBH) is synthesized and characterized by various physico-chemical and spectroscopic tools along with single crystal X-ray crystallography. This is the first report which describes its solvatochromism in solution and the signaling behavior of deprotonated DBH for the determination of water content in acetonitrile through UV-visible absorption spectra. Addition of acetate ions in acetonitrile solution of DBH results in the formation of deprotonated DBH. The effect of water content on the formation of deprotonated DBH is utilized in signaling. The deprotonated DBH exhibits a pronounced chromogenic signaling behavior that can be detected by the naked eye in response to the changes in water content in acetonitrile. Prominent color changes are observed up to 2% water content in acetonitrile and limit of detection (LOD) of the deprotonated DBH for determination of the water content in acetonitrile is calculated as 0.012%.

Colorimetric Signaling of Water Content in Acetonitrile by Phenolic Dye-Fluoride Complexes

E-mail: skchang@cau.ac.krReceived June 27, 2011, Accepted July 27, 2011Key Words : Water content, Acetonitrile, Phenolic dye-fluoride complex, Colorimetry, RatiometryPrecisely determining and controlling the water content ofchemicals and other commercial products are importantconsiderations in multiple fields of chemistry and industrialprocesses.

Chromogenic signalling of water content in organic solvents by hydrazone–acetate complexes

New chromogenic probe systems for the signalling of the water content in representative water-miscible organic solvents (acetonitrile and tetrahydrofuran) were investigated. The effect of the water content in organic solvents on the complex formation of hydrazone dye with acetate ions was utilized for the signalling. The hydrazone–acetate system exhibited a pronounced chromogenic signalling behaviour that could be detected by eye in response to the changes in water content in such common water-miscible organic solvents as acetonitrile and tetrahydrofuran. Prominent colour changes were observed for up to 1 and 2% water content in acetonitrile and THF, respectively. Detection limits of the anthracene-based hydrazone–acetate system for determination of the water content in acetonitrile and tetrahydrofuran were 0.037 and 0.071%, respectively. The 7-hydroxycoumarin-based hydrazone–acetate system showed somewhat less sensitive signalling behaviour, with respective detection limits of 0.12 and 0.63% in acetonitrile and tetrahydrofuran. The designed hydrazone–acetate systems could be used as a simple and convenient chromogenic probes for the determination of the water content in representative organic solvents of acetonitrile and tetrahydrofuran.

Ratiometric Determination of Water Content in Acetonitrile by a Fluorescein Derivative Bearing Two Pyrene Subunits

Ratiometric Determination of Water Content in Acetonitrile by a Fluorescein Derivative Bearing Two Pyrene Subunits

Investigation of the Hydrolysis of Lithium Bis[1,2-oxalato(2-)-O,O′] Borate (LiBOB) in Water and Acetonitrile by Conductivity and NMR Measurements in Comparison to Some Other Borates

The hydrolysis of lithium bis[1,2-oxalato(2-)-O,O′] borate (LiBOB) was investigated in pure water and in solutions of acetonitrile at low water content. The reaction in pure water can easily be observed by time-dependent conductivity measurements as protons are generated in the first step of hydrolysis. The results of these measurements can be evaluated according to a reaction of pseudo first order. Hydrolysis of other lithium borates in water was also studied for comparison. In acetonitrile as solvent, hydrolysis is much more complicated. NMR studies show a very slow reaction of LiBOB with water resulting in equilibria, depending on the water content of acetonitrile. Temperatures of 60 °C and water contents of several percent are necessary to achieve observable effects.

Enzyme-catalysed hydrolysis of L-amino acid esters in a low water organic solvent studied by isothermal calorimetry

Isothermal calorimetry and UV-visible spectrophotometry have been used to study the thermochemistry of the enzyme-catalyzed hydrolysis of hydrophobic L-amino acid esters in organic solvents with low water content at 298 K. The p-nitrophenyl esters of Z-L-tyrosine and Z-L-phenylalanine were used as model hydrophobic substrates. Acetonitrile was used as a model organic solvent. A special preparation protocol of the reactants in the calorimetric vessel was applied in order to determine the heat effects accompanying the enzyme-catalyzed hydrolysis reaction in organic mixtures with low water content and the Tris buffer ionization enthalpies over the whole range of water content in acetonitrile. It was found that the molar enthalpy of the hydrolysis of p-nitrophenyl esters and buffer ionization enthalpy depend significantly and similarly on the water content in acetonitrile. However, the reaction enthalpy corrected for the buffer ionization enthalpy does not depend on the water content in organic solvent mixtures. An explanation of the effect of the selected organic solvent on the thermochemical parameters was provided on the basis of the IR spectroscopic data for the hydrogen bond network of water in acetonitrile. The results obtained show that the state of water in organic solvents is an important factor that determines the reaction enthalpy as well as buffer ionization enthalpy.

A Simple Ratiometric Probe System for the Determination of Water Content in Organic Solvents

Determination of water content in organic solvents is very important in many of chemical processes and industrial applications. Chromatography and Karl Fischer titration are one of the most widely used techniques for this purpose. However, chemosensors are more convenient and simple to use in routine laboratory manipulations. Among the chemosensing systems, chromogenic or fluorogenic sensors are particularly attractive due to their easy of signaling and signal transducing method. Many interesting sensing systems have been reported including merocyanine dyes, chromone, flavone derivatives, membrane and opticalfiber sensor employing acridine dyes, and metal complex of Ru(bpy)(CN)4 , and are well reviewed in recent report. Fluorescein and its related compounds are known to have an interesting fluorescence signaling behavior in many biological systems. The spectral properties of fluorescein derivatives are strongly affected by the microenvironments and seems to be promising as molecular probes for the assessment of polarity of the biological systems. Particularly, it is well-known that the fluorescence of some fluorescein derivatives is strongly dependent on the media and the presence of a specific chemical stimulus. Based on this, we tried to elucidate the possibility of the fluorescein for the signaling of water content in common organic solvents. In preliminary studies, the UV-vis and fluorescence spectra of fluorescein 1 were found to be significantly affected in response to the increase in water content in common organic solvents. The significant fluorescence signaling behavior of the fluorescein was ratiometrically analyzed in reference to the relatively unaffected fluorescence of anthracene as an internal standard. In fact, the devised system exhibited a sensitive ratiometric fluorogenic behavior in response to the changes in water content of acetone and acetonitrile. First, UV-vis spectral behavior of the fluorescein 1 was studied in aqueous acetonitrile (Figure 1). In 100% acetonitrile solution, compound 1 exhibited no significant absorption band above 400 nm, which means that the fluorescein exists mainly in lactone form. As the water content increased, a strong absorption band around 452 and 488 nm emerged and steadily increased. That might be due to the shift in equilibrium of 1 toward ring-opened form over spectroscopically inactive lactone form. The changes in absorbance at 488 nm were not so pronounced up to 5% water then a significant enhancement was observed with further increasing water content in acetonitrile. Next, the changes in fluorescence of fluorescein in response to the water content in aqueous acetonitrile were measured. As discussed earlier, the fluorescence of 1 was strongly dependent on the water content in aqueous organic solvents. In 100% acetonitrile, compound 1 exhibited a very weak fluorescence around 541 nm, which is due to the fact that the fluorescein exists predominantly in lactone form in organic solvents. As the water content increased up to around 2%, the emission of 1 was significantly enhanced (20-fold) with some blue shift to 529 nm. In response to the further increase in water content from 2 to 50%, further blue shift in absorption maximum from 529 to 521 nm with another large (5.5-fold) fluorescence enhancement was observed. The chemosensing behavior of fluorescein was found to be efficient and a sensitive signaling of water content in aqueous acetonitrile seems to be realizable. However, the

Acetonitrile as Adsorbate or Solvent to Probe the Crystal Face Specificity of Metal–Water Interaction at Silver Electrode/Solution Interfaces

The crystal face specificity of metal–water interaction at Ag electrode/solution interfaces is investigated by using acetonitrile (ACN) as a probe molecule of the water interfacial structure or as a solvent in which water is a solute. Capacitance and voltammetric curves suggest that ACN is weakly adsorbed from aqueous solution on Ag in the order (111) > (100) > (110). Apparent inconsistencies of adsorption parameters are explained by the occurrence of two ACN adsorption modes: (i) directly on the metal surface and (ii) on the water layer adsorbed on the metal surface. Ag surface oxidation in ACN in the presence of variable amounts of water suggests that water has an inhibiting effect on Ag oxidation, the diminution of the water content in ACN leading to free anodic dissolution of the metal surface.

Electrochemically mediated enzyme reaction of polyethyleneglycol-modified galactose oxidase in organic solvents

This paper describes an electrochemically mediated enzyme reaction of polyethyleneglycol (PEG)-modified galactose oxidase (GAO) in organic solvents as well as in an aqueous solution. Catalytic currents were investigated in the presence of ferrocene derivatives as mediators and PEG-modified GAO in several organic solvents. The catalytic current due to the mediated enzyme reaction was obtained in acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide and dimethylsulfoxide (DMSO). Stability tests of PEG-modified GAO in organic solvents demonstrated that the initial Ik/Id value was highest in acetonitrile; however, it gradually decreased. The PEG-modified GAO was more stable in DMSO. Reactivities of several mediators were investigated. Although a positively charged mediator indicated high reactivity in the aqueous solution, non-charged mediators such as ferrocene dimethanol and n-butyl ferrocene showed the highest activity in organic solvents. Substrate specificity demonstrated that the catalytic activity for benzyl alcohol in acetonitrile was greater than in aqueous solution. The effect of water content in acetonitrile was investigated. The catalytic activity decreased with the increase in water content.

Regioselectivity in the semiconductor-mediated photooxidation of 1,4-pentanediol

Optimum conditions have been established for the selective semiconductor-photocatalyzed oxidation by long-wavelength ultraviolet light of the primary alcohol functionality in 1,4-pentanediol. On platinized (2%) TiO{sub 2} powder suspended in oxygenated aqueous (4 vol %) acetonitrile, the initial rate ratio for oxidation of the primary/secondary alcohol site was >7. Analysis of further oxidation products allowed for mechanistic delineation of the course of the semiconductor-mediated reaction. The selectivity is attributed to the essential role of adsorption, with the critical photoinduced electron transfer occurring at the surface of the irradiated particle. ZrO{sub 2} and SnO{sub 2} samples were much less active than TiO{sub 2} as photocatalysts. The effects of oxygen pressure, metal cocatalyst loading, and water content of acetonitrile are discussed.

Catalysed decomposition of bis(ethoxythiocarbonyl) sulphide with tributylphosphine. A kinetic study in dimethyl sulphoxide, acetonitrile, and their mixtures with toluene

The reaction of bis(ethoxythiocarbonyl) sulphide (1) with tributylphosphine in acetonitrile, dimethyl sulphoxide, and in their mixtures with toluene was subjected to kinetic study. The effect of water content in acetonitrile was also investigated. Activation parameters were measured and related to charge development in the formation of the first transition state, in accord with the proposed mechanism.