Organic Solvent Molecules Research Articles

クラスレート形成能を有する複素環キノール系蛍光色素の固体光物性と機能性

Organic fluorescent hosts which can exhibit sensitive color and fluorescence changes upon formation of host-guest inclusion complexes in the crystalline state can be one of the most promising materials for the construction of desirable solid-state fluorescent system and are attractive materials for their potential applications in analytical and material sciences. For this purpose, we have designed and synthesized several kind of heterocyclic quinol-type fluorescent hosts, (benzofurano[1,2-d]naphthoquionl-type, benzo[kl]xanthenol-type, benzofurano[3,2-b]naphthoquinol-type, and imidazo[5,4-a]anthraquinol-type fluorophores) whose crystals exhibit a dramatic fluorescence enhancement upon inclusion of various kinds of organic solvent molecules. The magnitude of the solid-state fluorescence enhancement is greatly dependent on the enclathrated guest molecules. It is confirmed from the spectral data and the X-ray crystal structures that the destruction of the host-host π-π interactions by the enclathrated guest molecules is the main reason for the guest-dependent fluorescence enhancement behavior. Furthermore, we found that these heterocyclic quinol-type fluorescent clathrands exhibit color and fluorescence changes upon exposure to various solvent vapors both in the crystalline state and thin-film state. We believe that these results are useful for the development of new solid-emissive chemosensors and for the improvement of pigmentary solid-state fluorescence in the applied field of optoelectronic devices.

Solid‐State Fluorescence Changes of 2‐(4‐Cyanophenyl)‐5‐[4‐(diethylamino)phenyl]‐3H‐imidazo[4,5‐a]naphthalene upon Inclusion of Organic Solvent Molecules

AbstractNovel imidazo[4,5‐a]naphthalene‐type fluorescent clathrate host 2‐(4‐cyanophenyl)‐5‐[4‐(diethylamino)phenyl]‐3H‐imidazo[4,5‐a]naphthalene (2), with two possible tautomeric forms (A and B) of the imidazole ring, was developed. The crystal of fluorophore 2 exhibits sensitive colour change and fluorescence enhancement behaviour with a blueshift in the emission maximum upon enclathration of various kinds of organic solvent molecules. The crystal structures of the guest‐free and clathrate compounds of 2 were determined by X‐ray analysis. On the basis of spectroscopic data and crystal structures, the effects of the enclathrated guest on the solid‐state photophysical properties of the clathrate compounds are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Micro-solvent Cluster Extraction Using Aqueous Mixed Solvents of Ionic Liquid

Organic compounds (2-naphthol, phenol, 4-chlorophenol, 4-nitrophenol, and 1,3,5-naphthalenetrisulfonic acid) were sufficiently separated from mixtures during flow in a fused silica capillary tube (50 microm in i.d. and 45 cm in length) with an aqueous mixed solvent of an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIM(+)Cl(-)), without a specific separation column. The method is based on micro-solvent cluster formation in aqueous mixed solvents of ionic liquid and preferential solvation of solvent clusters to analytes. The measurement of large angle X-ray scattering (LAXS) of aqueous mixed solvents with an ionic liquid of tetrafluoroborate (BMIM(+)BF(4)(-)) indicated the formation of micro-solvent clusters of water and ionic liquid in the mixed solvent. A neutral polymer (polyvinylpyrrolidone, PVP) enhanced the separation. Polarized or ionic molecules eluted slowly. The theoretical plate numbers were 6320, 22907, 63645, and 37184 for 2-naphthol, phenol, 4-chlorophenol, and 4-nitrophenol, respectively, under the conditions of 1.0 M of BMIM(+)Cl(-) and 0.1 M of PVP; the flow rate was 1 microL min(-1). The separation mechanism is discussed from the viewpoint of the partition of analytes between micro-solvent clusters of water and organic solvent molecules.

The enthalpies of solution of L-α-alanyl-L-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (T = 298.15 K) of L-α-alanyl-L-α-alanine in aqueous-organic solvents (acetonitrile, 1,4-dioxane, acetone, formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, and N,N-dimethylsulfoxide) were measured at organic component concentrations x2 = 0–0.3 mole fractions. The standard enthalpies of solution (ΔsolHo) and transfer (ΔtrHo) of the peptide from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics is considered. The enthalpy pair interaction coefficients hxy between L-α-alanyl-L-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft four-parameter equation was used to reveal correlation between the hxy values and the properties of organic solvents.

Fluorescent Gel from a Self-Assembling New Chromophoric Moiety Containing Azobenzene Based Tetraamide

A new chromophoric low molecular weight (LMW) organic molecule, 1, was synthesized, and it forms gels in various organic solvents including toluene, o-xylene, m-xylene and p-xylene. The resultant gel phase materials exhibit enhanced and red-shifted fluorescence emission in the respective gelling solvents. This gelator molecule is self-assembled using various noncovalent interactions including hydrogen bonding, pi-pi staking and van der Waals interactions to get the gel phase materials. The molecule 1 is very weakly fluorescent in solution, but its intensity is increased by almost 40 times in their respective gelled state depending on the nature of the gelling solvents. Self-assembly of this molecule in the above-mentioned organic solvents gives an elongated nanofibrillar network that can be visualized through Field Emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM).

PEGylated nanographene oxide for delivery of water-insoluble cancer drugs.

It is known that many potent, often aromatic drugs are water insoluble, which has hampered their use for disease treatment. In this work, we functionalized nanographene oxide (NGO), a novel graphitic material, with branched polyethylene glycol (PEG) to obtain a biocompatible NGO-PEG conjugate stable in various biological solutions, and used them for attaching hydrophobic aromatic molecules including a camptothecin (CPT) analogue, SN38, noncovalently via pi-pi stacking. The resulting NGO-PEG-SN38 complex exhibited excellent water solubility while maintaining its high cancer cell killing potency similar to that of the free SN38 molecules in organic solvents. The efficacy of NGO-PEG-SN38 was far higher than that of irinotecan (CPT-11), a FDA-approved water soluble SN38 prodrug used for the treatment of colon cancer. Our results showed that graphene is a novel class of material promising for biological applications including future in vivo cancer treatment with various aromatic, low-solubility drugs.

Heterocyclic Quinol‐Type Fluorophores: Solid‐State Fluorescence Change in Crystals of Benzo[b]naphtho[1,2‐d]furan‐6‐one‐Type Fluorophore upon Inclusion of Organic Solvent Molecules

AbstractThe crystals of benzo[b]naphtho[1,2‐d]furan‐6‐one‐type fluorophores (1) exhibit sensitive colour and fluorescence change upon enclathration of organic solvent molecules. The crystal of fluorophore 1b (R = Bu) exhibits fluorescence decrease upon inclusion of cyclohexane; however, the crystal of fluorophore 1c (R = Ph) exhibits a drastic fluorescence enhancement upon inclusion of chloroform. To elucidate the enclathrated guest effects on the photophysical properties of the crystals, the X‐ray crystal structures of the guest‐free and guest‐inclusion compounds were determined. On the basis of the spectroscopic data and the crystal structures, the effects of the enclathrated guest on the solid‐state photophysical properties of the clathrate compounds are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Desolvaton of Zinc(II)tetra-tert-butylphthalocyanine Crystal Solvates as Probed by Thermogravimetry

Kinetic analysis of the thermal destruction of complexes of zinc(II)tetra-tert-butylphthalocyanine Zn(t-Bu)4Pc with organic solvent molecules has been carried out. For ligands having high ionization potentials, long refluxing of solution is required for preparing biligand complexes. For molecular ligands whose ionization potentials do not exceed 9.2 eV, the composition of complexes with Zn(t-Bu)4Pc is independent of the preparation parameters. The destruction of the Zn(t-Bu)4Pc complexes with n-propylamine, diethylaniline, piperidine (1: 1, cold synthesis), diethylamine, morpholine, quinoline, or cyclopentanone (1: 2, hot synthesis; 1: 2, cold synthesis) obeys fist-order equations; for complexes with pyridine, 1,4-dioxane, DMF, cyclopentanone (1: 1, hot synthesis), 3-dimethylaminopropionitrile, or piperidine (1: 2, hot synthesis), destruction obeys second-order equations. The activation energies of thermal destruction for the first group of molecular complexes fall in the range from 89 to 370 kJ/mol; the rate-controlling stage is nucleation and growth. For the second group, the activation energies fall in the range from 160 to 640 kJ/mol; the rate-controlling stage is a chemical reaction.

The interplay of coordinative and hydrogen-bonding in directing the [M(4,4′-bpy)2(H2O)2] square-grid networks: formation of 3D porous framework [Cd(4,4′-bpy)2(H2O)2](ClO4)2(4,4′-bpy)(CH3OH)2

The reaction of 4,4′-bipyridine (4,4′-bpy) with Cd(ClO)2 leads to an assembly of the two-dimensional (2D) square-grid networks, [Cd(4,4′-bpy)2(H2O)2](ClO4)2, which stack in a slightly offset parallel fashion in the crystal lattice directed by hydrogen-bonding 4,4′-bpy spacers to sustain a self-catenated three-dimensional (3D) framework, [Cd(4,4′-bpy)2(H2O)2](ClO4)2(4,4′-bpy)(CH3OH)2 (1). The rectangular channels (11.8 × 10.4 A, atom-to-atom separation) are formed where the ClO4− anions and organic solvent molecules are hosted. The interplay of the coordinative and hydrogen-bonding interactions in directing crystal packing of the [M(4,4′-bpy)2(H2O)2] square-grid networks have been analyzed in comparison with known examples.

Investigation of mechanism of organic solvent vapours sensing effect in polyisoprene-high structure carbon black composite

A study of detecting organic vapour environments of nine different solvents by polyisoprene-high structured carbon composite (PHSCBC) sensors is reported. The electric resistance of the composite is found to be increased as soon as it contacts the vapour and to return to the initial value after being removied from the environment. To reveal the mechanism of the effect, simultaneous measurements of electrical resistance, elongation, and changes caused by sorption of organic solvent molecules in the bulk of PHSCBC samples were made in real time. From sorption experiments it has been found that the increase of electric resistance is generally dominated by absorption of solvent molecules in the matrix material, subsequently swelling it up and increasing the distance between conductor particles. The experiments prove that a remarkable and rapid change of the resistance could be explained by change of the tunnelling currents between adjacent carbon nano-particles.

Maintaining bioactivity of NGF for controlled release from PLGA using PEG

The goal of this work was to investigate methods to retain bioactivity of nerve growth factor (NGF) after encapsulation in poly(lactic-co-glycolic acid) (PLGA) discs for controlled release. Poly(ethylene glycol) (PEG) was chosen as a porogen not only to control the release rate of NGF but also because it has been used to help maintain bioactivity of molecules in organic solvents. NGF and PEG were encapsulated in PLGA via standard dissolution-evaporation techniques with methylene chloride as the solvent. Morita et al. (Pharm Res 2000; 17:1367-1373) indicated that colyophilization of PEG and bioactive factors before exposure to organic solvents increased the retention of bioactivity. Therefore, various PEG:NGF mass ratios were colyophilized before encapsulation within PLGA to examine retained activity of NGF. When PEG was not colyophilized before encapsulation, NGF activity was lost during the fabrication process. In contrast, colyophilization of PEG and NGF supported retention of NGF activity during the entire fabrication process. The amount of PEG encapsulated was the dominating factor in the rate of NGF release regardless of the fabrication method. These results demonstrate the usefulness of PEG in both acting as a porogen to modulate release and aiding in the retention of activity of NGF. This process may be extended to other methods to enhance activity of growth factors after exposure to organic solvents.

A new polythiophene derivative with highly sensitive and selective affinitychromism properties

A new poly(3-alkyl)thiophene bearing a piperidinic moiety in the side chain was synthesized in different ways with satisfactory yields in soluble fractions at high molecular weights. The chromic behaviors of the different polymeric samples were studied by UV–vis spectroscopy in different solvent/non-solvent mixtures and in the presence of some analytes; a strong affinitychromism toward bicarboxylic acids was observed. The good chromic response and its independence from the structural parameters of the polymer indicate the development of a very useful and easily obtainable colorimetric tool for the quick, sensitive and selective detection of diacid molecules in organic solvents.

The thermochemical characteristics of solution of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine in water-organic solvent (acetonitrile, 1,4-dioxane, acetone, N,N-dimethylformamide, and N,N-dimethylsulfoxide) mixtures were measured at organic component concentrations x 2 = 0–0.4 mole fractions and T = 298.15 K. The standard enthalpies of solution (Δsol H°) and transfer (Δtr H°) of the peptides from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on the thermochemical characteristics of the peptides was considered. The enthalpy coefficients of pair interactions (h xy ) of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine with organic solvent molecules were calculated. The h xy values were correlated with the properties of organic solvents using the Kamlet-Taft equation.

Nitrogen-containing carbon spheres with very large uniform mesopores: The superior electrode materials for EDLC in organic electrolyte

We reported the electrochemical studies on mesoporous carbon spheres (MCS) enriched in nitrogen on frameworks serving as an electrode for electric double layer capacitor (EDLC) in an organic electrolyte. The preparation of the carbon spheres is involved in a facile polymerization-induced colloid aggregation method by using melamine-formaldehyde resin (MF) as the carbon precursor, and commercial fumed silica (Aerosil-200) as a hard template. After the carbonization of as-formed resin-template composites at 1000 °C under a nitrogen atmosphere, and the removal of silica template by HF treatment, monodisperse MCS with diameter size of ∼1.2 μm, high specific surface area (up to 1460 m 2/g) and uniform pore size as large as 31 nm can be obtained. The MCS product presents a high specific capacitance as 159 F/g at 0.5 A/g. The high specific capacitance of the MCS is believed to be associated with its suitable nitrogen content that can afford pseudocapacitance as well as the high specific surface area. Furthermore, the specific capacitance of MCS can remain 130 F/g at high current density of 20 A/g. Our results show that the moderate nitrogen content can enhance the surface wettability and reduce the resistance, the large pore size can accelerate the diffusion process for the ions solvated with big organic solvent molecules in the pores. In view of the facts that precursors used in this simple process are commercially available low-cost chemicals, researches on the synthesis of such MCS materials templated by silica nanoparticles may not only be theoretically important, but also provide more options for economical and large-scale productions of mesoporous carbon materials with desired nanostructures, which might find practical applications in the fields of EDLC with high power performance.

7-Isopropyl-5-methyl-1,3,5-triazepan-2,6-dione deuterated chloroform 0.94-solvate

The title compound, C8H15N3O2.0.94CDCl3, displays a folded conformation and cocrystallizes with deuterated chloro­form mol­ecules. The asymmetric unit contains two triazepan molecules and two solvent molecules with incomplete occupancy. The expected absolute configuration was confirmed from the Flack parameter using anomalous dispersion. Mol­ecules are linked by hydrogen bonds to form infinite planes which are perpendicular to the c axis. The network of these planes is sandwiched by a layer of organic solvent molecules through hydrogen bonds and van der Waals inter­actions.

Stability of Nucleic Acid Base Pairs in Organic Solvents: Molecular Dynamics, Molecular Dynamics/Quenching, and Correlated Ab Initio Study

The dynamic structure and potential energy surface of adenine...thymine and guanine...cytosine base pairs and their methylated analogues interacting with a small number (from 1 to 16 molecules) of organic solvents (methanol, dimethylsulfoxide, and chloroform) were investigated by various theoretical approaches starting from simple empirical methods employing the Cornell et al. force field to highly accurate ab initio quantum chemical calculations (MP2 and particularly CCSD(T) methods). After the simple molecular dynamics simulation, the molecular dynamics in combination with quenching technique was also used. The molecular dynamics simulations presented here have confirmed previous experimental and theoretical results from the bulk solvents showing that, whereas in chloroform the base pairs create hydrogen-bonded structures, in methanol, stacked structures are preferred. While methanol (like water) can stabilize the stacked structures of the base pairs by a higher number of hydrogen bonds than is possible in hydrogen-bonded pairs, the chloroform molecule lacks such a property, and the hydrogen-bonded structures are preferred in this solvent. The large volume of the dimethylsulfoxide molecule is an obstacle for the creation of very stable hydrogen-bonded and stacked systems, and a preference for T-shaped structures, especially for complexes of methylated adenine...thymine base pairs, was observed. These results provide clear evidence that the preference of either the stacked or the hydrogen-bonded structures of the base pairs in the solvent is not determined only by bulk properties or the solvent polarity but rather by specific interactions of the base pair with a small number of the solvent molecules. These conclusions obtained at the empirical level were verified also by high-level ab initio correlated calculations.

Pervaporation properties of fluoroalkylsilane (FAS) grafted ceramic membranes

Changing the hydrophilic character of ceramic membranes into hydrophobic ones is nowadays of particular interest. The originally hydrophilic character of ceramic membranes can be changed by grafting hydrophobic molecules on the surface. Fluoroalkylsilanes (FAS) are a group of compounds which can be efficiently used to create the hydrophobic character of different surfaces. The grafting process can be performed by a reaction between -OH surface groups of the ceramics and ethoxy groups (-O-Et) presented in organosilane compounds. The aim of this work was to prepare FAS-modified pervaporation ceramic membranes by grafting alumina and/or titania ceramic nanofiltration membranes with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (C8) molecules and to determine the properties of such modified hydrophobic ceramic membranes in the pervaporation process used for the desalination of different salt solutions and for the removal of organic solvents of different hydrophobicity [i.e., ethanol (EtOH) and methyl t-butyl ether (MTBE)] from water. It was found that transport and selective properties of grafted membranes depended on the type of ceramics and the grafting conditions. In general, FAS grafted titania membranes were more permeable and more selective than alumina ones. In the case of desalination it was found that salt rejection was practically 100%; there was no salt found in the permeate. Pervaporation flux in contact with an aqueous salt solution was dependent on the kind of salt, its concentration and feed temperature. FAS grafted membranes prepared from titania showed much higher permeation fluxes compared with alumina ones. Both membranes showed high selectivity towards the organic component of water–organic mixtures. The selectivity factor of FAS-TiO 2 (grafted in 0.1 M C8), FAS-TiO 2 (grafted in 0.01 M C8) and FAS-Al 2O 3 (grafted in 0.01 M C8) membranes in contact with water–MTBE (2 wt.% MTBE) solution was 95, 45 and 23, respectively. The C8 molecules grafted on the titania ceramics underwent conformation change from a tangled form into the straightened one when the C8 environment changed from pure water to a water–organic or water–electrolyte solution. The concentration range in which this conformation change occurred was dependent on the hydrophobicity of organic solvent molecules presented in the solution. In the case of more hydrophobic MTBE molecules the tangled–straightened form change of FAS molecules occurred in a concentration range 0–0.1 mol. % MTBE.

Microinhomogeneity for Aqueous Mixtures of Water-miscible Organic Solvents

Mixing states for aqueous solutions of water-miscible organic solvents, acetonitrile and 1,4-dioxane, have been investigated at the molecular level by means of small-angle neutron scattering (SANS) and NMR relaxation. It has been shown that the organic solvent and water molecules are inhomogeneously mixed each other at the molecular level, although their mixtures are homogeneous at the macroscopic scale. Thus, both organic solvent clusters and water clusters coexist in the mixtures. The present investigation has also revealed that the microinhomogeneity of acetonitrile-water and 1,4-dioxane-water mixtures is gradually enhanced by cooling or adding salts toward phase separation. Based on the results, the effect of microinhomogeneity for solvent mixtures on chemical reactions was considered.

Kinetics of codeposition of copper with N-methylpyrrolidone in sulfate water-dimethylsulfoxide electrolytes

The electrolyte composition is found to affect the composition and density of the adsorption layer on the electrode. The lowest process rate is observed in the water structure stabilization range under conditions of the preferential adsorption of the additive and organic solvent molecules. The electroreduction of copper(II) ions involves the stage of their penetration through the adsorption film, while the dissociation of electroactive species, which precedes their discharge, has the “forced” nature. The increase in the adsorption activity of sulfate ions (which is due to the “salting-out” effect of the mixed solvent and the selective solvation) is accompanied by the acceleration of the process (the ψ effect or the formation of surface associated products, in which anions play the role of bridge ligands).

Interactions of Hexafluoro-2-propanol with the Trp-Cage Peptide

Fluoro alcohols present in aqueous solutions can alter the dominant conformations of peptides and proteins. The origins of these effects likely are related to the details of solute-fluoro alcohol interactions. Preferential interaction of the fluoro alcohol component of a fluoro alcohol-water mixture with peptide solutes has been demonstrated by several experimental approaches. In the present work, we have used 1H{19F} intermolecular NOE experiments to examine interactions of hexafluoro-2-propanol in a 30% fluoro alcohol-50 mM phosphate buffer solvent mixture with the "Trp-cage" peptide (NLY IQW LKD GGP SSG RPP PS). The results show that the peptide is selectively solvated by hexafluoro-2-propanol to the extent that the fluoro alcohol concentration near the peptide may be 3 to 4 times higher than the nominal concentration of fluoro alcohol in the bulk sample. The observed NOEs indicate that peptide-fluoro alcohol interactions persist for times of the order of 1 ns at 5 degrees C. As the sample temperature is increased, the lifetimes of fluoro alcohol interactions with several exposed side chains decrease to the extent that the peptide hydrogen-solvent fluorine interactions appear to become diffusive in nature, with interaction lifetimes of approximately 0.03 ns. It is known that protein molecules can provide specific sites for binding small organic solvent molecules. Our work suggests that small peptides also have this ability and that the dynamics for such interactions can be site-specific.