DMSO-water Mixtures Research Articles

Highly efficient fluorescence switching of carbon nanodots by CO2

In recent years, carbon nanodots (CDs) have attracted increasing attention in many applications because of their superior optical and chemical properties. To manipulate CDs properties for their smart applications, CDs with CO2 switchable luminescence property have been designed and prepared in the present work. It is found that fluorescence of the polyamine-functionalized CDs can be switched “off” and “on” in DMSO-water mixture by alternatively bubbling and removal of CO2. 13C NMR spectra suggest that the mechanism behind the fluorescence “on-off” results involves the reversible acid-base reaction of the functionalized CDs with CO2 and the formation of hydrophilic polyammonium bicarbonates. Due to the poor solubility of polyammonium bicarbonates in DMSO-water mixture, the formation of the polyammonium bicarbonates precipitation, by CO2 bubbling, decreases the concentration of the functionalized CDs in aqueous DMSO, leading to the switch off of the fluorescence. When CO2 is removed by N2 bubbling, the precipitation is returned to the DMSO-water mixture, and thereby the fluorescence is switched on again. Based on this novel CO2-switchable photoluminescence property, the functionalized CDs have been used for the quantitative detection of CO2 and SO2 in aqueous solution and in the air.

A selective chemosensor for fluoride ion and its interaction with Calf Thymus DNA

The amido-Schiff base 1 (N1, N3-bis (2-nitrobenzylidene)benzene-1,3-dicabohydrazide) containing a CONH group and CHN linkage has been synthesized by the condensation between isophthalic acid dihydrazide and o-nitrobenzaldehyde. This molecule can act as a fluoride ion sensor with high selectivity and sensitivity. Presence of nitro group in the phenyl ring may be responsible for the detection of fluoride ion visually with a dramatic color change from colorless to deep red in aqueous dimethyl sulphoxide solution. This Schiff base can be used as test kit for sensing of fluoride ion in the solid state. Compound 1 can detect fluoride also in commercially available toothpaste. As the compound has adequate solubility in DMSO–water mixture (7:93, v/v) and having some hydrogen bond donor and acceptor centers, we have investigated its nature of binding with Calf Thymus-DNA (CT-DNA) using theoretical molecular modelling and other experimental methods like UV–vis spectroscopy, circular dichroic and thermal melting studies. Thermodynamic parameters have been obtained using the well known Van't Hoff's equation. From both theoretical and experimental findings it has been observed that it can interact effectively with CT-DNA with binding energy −7.55kcal/mol to −7.50kcal/mol.

Self-Assembly of Hydrophobic Polybetaine Based on (Tridecyl)aminocrotonate and Methacrylic Acid1, "Высокомолекулярные соединения. Серия С"

Novel polymeric betaine based on tridecylaminocrotonate and methacrylic acid was synthesized by Michael addition reaction. The obtained products were abbreviated as CROtriDA-MAA and with respect to its potassium salt as CROtriDA-MAA-K. The structure of CROtriDA-MAA was established by 1H NMR and FTIR spectroscopy. The hydrodynamic, molecular and conformational properties of CROtriDA-MAA-K in solutions and morphology in solid state were evaluated by methods of GPC, DLS, zeta-potential, surface enhanced ellipsoidal microscopy (SEEC), optical microscopy. Meanwhile, the long alkyl “tails” (tridecyl) located in side polymeric chains are responsible for self-assembling behavior. Several types of self-assembled structures in water at different pH and in water-DMSO mixture were observed. The dendritic structure with wide trunks and few side branches is formed at pH 3. The “Maltese cross-like” aggregates were found at pH 6.5. The tree-like fractal patterns are formed at pH 12. The self-assembled coiled-ribbon-like and tubular-like aggregates were observed in water-DMSO mixtures.

Acoustic and Thermo-Dynamical Investigation of 2-Amino-5-Nitrothiazole- DMSO-Water System at Different Temperatures and Concentration

Thiazole is Sulphur and nitrogen containing heterocyclic compounds represents an important family of medicines in the pharmaceutical chemistry having vast biological applications. Due to the presence of hetero atoms in 2-amino-5- nitrothiazole there should be various types of interaction, by undertaking these interactions, ultrasonic study of 2-amino- 5-nitrothiazole in 70:30 (v/v) DMSO-Water mixture at different concentration and temperature is carried out. Speed of sound and denseness of ternary mixture of 2-amino-5-nitrothiazole – 70:30 (v/v) DMSO-water systems has been measured at various temperature (303.15K, 308.15K, 313.15K and 318.15K) and concentrations, to get idea regarding the solute- solvent and solvent – solvent interaction. In present investigation ultrasonic parameters i.e., specific acoustic impedance, relative association intermolecular free length, adiabatic compressibility, and sound speed number has been put forward to say about types of molecular interaction present in the aqueous 70:30 (v/v) DMSO-water solution of various temperatures and concentrations. Strength of molecular interactions was studied with comparisons to change in temperature and change in concentration. The correlation observed represents interpreted in the form of solute-solvent and solvent-solvent interactions at given temperature variation and concentration variations.

Correction to "Polarizable Model for DMSO and DMSO-Water Mixtures".

Correction to "Polarizable Model for DMSO and DMSO-Water Mixtures".

Local lateral environment of the molecules at the surface of DMSO-water mixtures

Molecular dynamics simulations of the liquid–vapour interface of dimethyl sulphoxide (DMSO)-water mixtures of 11 different compositions, including two neat systems are performed on the canonical (N, V, T) ensemble at 298 K. The molecules constituting the surface layer of these systems are selected by means of the identification of the truly interfacial molecules (ITIM) method, and their local lateral environment at the liquid surface is investigated by performing Voronoi analysis. The obtained results reveal that both molecules prefer to be in a mixed local environment, consisting of both kinds of molecules, at the liquid surface, and this preference is even stronger here than in the bulk liquid phase. Neat-like patches, in which a molecule is surrounded by like neighbours, are not found. However, vacancies that are surrounded solely by water molecules are observed at the liquid surface. Our results show that strongly hydrogen bonded DMSO·H2O complexes, known to exist in the bulk phase of these mixtures, are absent from the liquid surface.

Polymer complexes. LXV. Potentiometry, theoretical and molecular docking studies of azo allylrhodanine derivatives and their metal complexes in monomeric and polymeric forms

Azo dyes of 3-allyl-5-((4-derivative phenyl)diazenyl)-2-thioxothiazolidin-4-one ligands (HLn) are synthesized and characterized using different spectroscopic techniques. The X-ray diffraction, XRD, pattern of the ligand (HL2) is polycrystalline nature. The geometrical structures of the ligand are carried out by HF method with 3-21G basis set. Molecular docking was used to predict the binding between azo dye ligand and the receptor of prostate cancer mutant 2q7k-hormone and the receptor of breast cancer mutant 3hb5-oxidoreductase. The predicted pKa obtained by docking measurements for the ligands are in agreement with experimental values. The predicted and expermently calculated pKH values of the ligands increases in the order HL3, HL2 and HL1 as expected from Hammett's constant (σR). The proton-ligand dissociation constants of HLn and their metal stability constants with Mn2+, Co2+, Ni2+ and Cu2+ have been determined potentiometrically in monomeric and polymeric forms using 2,2′-azobisisobutyronitrile as initiator. The potentiometric studies were carried out in 0.1M (KCl) and 50% (by volume) DMSO-water mixture. The effect of temperature was studied at 298, 308 and 318K and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable.

Crystal Engineering Applied to Modulate the Structure and Magnetic Properties of Oxamate Complexes Containing the [Cu(bpca)]+Cation

This work deals with the crystal engineering features of four related copper(II)-based compounds with formulas {[{Cu(bpca)}2(H2ppba)]·1.33DMF·0.66DMSO}n (2), [{Cu(bpca)(H2O)}2(H2ppba)] (3), [{Cu(bpca)}2(H2ppba)]·DMSO (4), and [{Cu(bpca)}2(H2ppba)]·6H2O (5) [H4ppba = N,N′-1,4-phenylenebis(oxamic acid) and Hbpca = bis(2-pyridylcarbonyl)amide] and how their distinct molecular and crystal structures translate into their different magnetic properties. 2 and 3 were obtained through the hydrolytic reaction of the double-stranded oxamato-based dipalladium(II) paracyclophane precursor of formula [{K4(H2O)2}{Pd2(ppba)2}] (1) with the mononuclear copper(II) complex [Cu(bpca)(H2O)2]+, either in a water–DMSO–DMF solvent mixture or in water, respectively. The straightforward reaction of the neutral H4ppba molecule with [Cu(bpca)(H2O)2]+ in a water–DMSO mixture afforded compound 4, whereas compound 5 resulted from the reaction between the copper(II) complex and the K2ppba salt in water. The [Pd2(ppba)2]4– tetraanionic u...

Na+ Cl− ion pair association in water-DMSO mixtures: Effect of ion pair model potentials

Potentials of Mean Force (PMF) for the Na+Cl− ion pair in water–dimethyl sulfoxide (DMSO) mixtures for three DMSO mole fractions have been computed using constrained Molecular Dynamics (MD) simulations and confirmed by dynamical trajectories and residence times of the ion pair at various inter-ionic separations. The three ion-ion direct potentials used are 12-6-1, exp-6-1 and exp-8-6-1. The physical picture that emerges is that there is a strong contact ion pair (CIP) and strong to moderate solvent separated ion pair (SSIP) in these solutions. Analysis of local ion clusters shows that ions are dominantly solvated by water molecules. The 12-6-1 potential model predicts running coordination numbers closest to experimental data. The effect of the differences between the 12-6-1, Huggins-Mayer (exp-6-1) and Fumi-Tosi (exp-6-8-1) ion-ion potential models on the solvation structure of the sodium chloride ion pair in water-DMSO binary mixtures have been studied.

Insights into the photophysics of zinc phthalocyanine and photogenerated singlet oxygen in DMSO-water mixture

This research was focused on the effects of DMSO-water ratio on the photophysics of the sensitizer Zn phthalocyanine (ZnPc) and on the photogenerated singlet oxygen. To reach this objective optical absorption, flash photolysis and time-resolved phosphorescence were used. Potential dye accumulation at the surface of the sample was studied by surface-tension measurements and at the chosen concentration no such effects were found. It was established that the sharp drop of dye absorbance at ∼40% water content is produced by dye dimerization, probably induced by a re-clustering of molecules in the solvent composition. When water runs over 0–80% range the dye triplet lifetime follows a sigmoid evolution with an inceptive plateau at 120μs and a sharp decrease in the 25–35% water range. Complementary experiments in neat DMSO established that while the ground dye molecules strongly quench the dye triplet states they do not significantly quench singlet oxygen. Experiments also showed that previous reported behavior of the lifetime of photosensitized singlet oxygen, exhibiting a prominent peak in the range 20–40% of water content is a common feature for both water soluble and insoluble solvates. The work outlines the hypothesis of a DMSO first solvation shell around the solvated dye molecules for a water content less than 25% and of a molecular re-organisation of the solvent taking place beyond this point, which induces important variations of photophysical quantities.

Cytotoxicity of platinum(IV) and palladium(II) complexes with meso-1,2-diphenyl-ethylenediamine-N,N'-di-3-propanoic acid. Crystal structure of [Pd(1,2-dpheddp)] complex

The syntheses of tetradentate ligand, meso-1,2-diphenyl-ethylenediamine-N,N'-di-3-propanoic acid (H2-1,2-dpheddp) and corresponding platinum(IV) and palladium(II) complexes are reported here. The spectroscopically predicted structure of the obtained palladium(II) complex was confirmed by X-ray analysis. Singe crystals suitable for X-ray measurements were obtained by slow crystallization from a DMSO-water mixture. Cytotoxic effects of platinum(IV), palladium(II) complexes and cisplatin on the 4T1 and B16F1 cell lines were determined using the MTT colorimetric technique. The complexes showed a dose dependence on cytotoxic effect toward both cell lines. Both complexes were less active than cisplatin, the exception was concentrations above 62.5 μM of platinum(IV) complex in the B16F1 cell line.

Potentiometric, thermodynamics and theoretical calculations of some rhodanine derivatives

A series of 5-(4′-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HLn) have been prepared and characterized by elemental analysis, 1H NMR and IR spectra. X-ray diffraction pattern of ligand (HL2) was studied. The geometrical structures of these ligands are carried out by HF method with 3-21G basis set. Proton-ligand dissociation constant of ligands (HLn) and their metal–ligand stability constants of Mn2+, Co2+, Ni2+ and Cu2+ have been determined potentiometrically in 0.1M KCl and 30% (v/v) DMSO–water mixture at 298, 308 and 318K. The stability constants of the formed complexes increase with the order: Mn2+<Co2+<Ni2+<Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable. Proton–ligand dissociation constant (pKH) of the ligands increases according to the following order p-(OCH3>H>NO2) as expected from Hammett's constant (σR).

Non-Ideal Behaviour and Solution Interactions in Binary DMSO Solutions.

The structure and dynamics of hydrogen-bonded structures are of significant importance in understanding many binary mixtures. Since self-diffusion is very sensitive to changes in the molecular weight and shape of the diffusing species, hydrogen-bonded associated structures in dimethylsulfoxide-methanol (DMSO-MeOH) and DMSO-ethanol (DMSO-EtOH) mixtures are investigated using nuclear magnetic resonance (NMR) diffusion experiments and molecular dynamics (MD) simulations over the entire composition range at 298 K. The self-diffusion coefficients of DMSO-MeOH and DMSO-EtOH mixtures decrease by up to 15% and 10%, respectively, with DMSO concentration, indicating weaker association as compared to DMSO-water mixtures. The calculated heat of mixing and radial distribution functions reveal that the intermolecular structures of DMSO-MeOH and DMSO-EtOH mixtures do not change on mixing. DMSO-alcohol hydrogen-bonded dimers are the dominant species in mixtures. Direct comparison of the simulated and experimental data afford greater insights into the structural properties of binary mixtures.

Correlating steric hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid–DMSO–H2O system

Dimethyl sulfoxide (DMSO) is a common solvent and biological additive possessing well-known utility in cellular cryoprotection and lipid membrane permeabilization, but the governing mechanisms at membrane interfaces remain poorly understood. Many studies have focused on DMSO-lipid interactions and the subsequent effects on membrane-phase behavior, but explanations often rely on qualitative notions of DMSO-induced dehydration of lipid head groups. In this work, surface forces measurements between gel-phase dipalmitoylphosphatidylcholine membranes in DMSO-water mixtures quantify the hydration- and solvation-length scales with angstrom resolution as a function of DMSO concentration from 0 mol% to 20 mol%. DMSO causes a drastic decrease in the range of the steric hydration repulsion, leading to an increase in adhesion at a much-reduced intermembrane distance. Pulsed field gradient NMR of the phosphatidylcholine (PC) head group analogs, dimethyl phosphate and tetramethylammonium ions, shows that the ion hydrodynamic radius decreases with increasing DMSO concentration up to 10 mol% DMSO. The complementary measurements indicate that, at concentrations below 10 mol%, the primary effect of DMSO is to decrease the solvated volume of the PC head group and that, from 10 mol% to 20 mol%, DMSO acts to gradually collapse head groups down onto the surface and suppress their thermal motion. This work shows a connection between surface forces, head group conformation and dynamics, and surface water diffusion, with important implications for soft matter and colloidal systems.

ChemInform Abstract: Synthesis of Indoles, Benzofurans, and Related Heterocycles via an Acetylene‐Activated SNAr/Intramolecular Cyclization Cascade Sequence in Water or DMSO.

The synthesis of 2-substituted indoles and benzofurans was achieved by nucleophilic aromatic substitution, followed by subsequent 5-endo-dig cyclization between the nucleophile and an ortho acetylene. The acetylene serves the dual role of the electron withdrawing group to activate the substrate for SNAr, and the C1–C2 carbon scaffold for the newly formed 5-membered heteroaromatic ring. This method allows for the bond forming sequence of Ar–X–N/O–C1 to proceed in a single synthetic step, furnishing indoles and benzofurans in moderate to high yields. Since the method is not transition metal mediated, brominated and chlorinated substrates are tolerated, and benzofuran formation can be conducted using water or water–DMSO mixtures as solvent.

Femtosecond mid-infrared study of the dynamics of water molecules in water-acetone and water-dimethyl sulfoxide mixtures.

We study the vibrational relaxation dynamics and the reorientation dynamics of HDO molecules in binary water-dimethyl sulfoxide (DMSO) and water-acetone mixtures with polarization-resolved femtosecond mid-infrared spectroscopy. For low solute concentrations we observe a slowing down of the reorientation of part of the water molecules that hydrate the hydrophobic methyl groups of DMSO and acetone. For water-DMSO mixtures the fraction of slowed-down water molecules rises much steeper with solute concentration than for water-acetone mixtures, showing that acetone molecules show significant aggregation already at low concentrations. At high solute concentrations, the vibrational and reorientation dynamics of both water-DMSO and water-acetone mixtures show a clear distinction between the dynamics of water molecules donating hydrogen bonds to other water molecules and the dynamics of water donating a hydrogen bond to the S═O/C═O group of the solute. For water-DMSO mixtures both types of water molecules show a very slow reorientation. The water molecules forming hydrogen bonds to the S═O group reorient with a time constant that decreases from 46 ± 14 ps at XDMSO = 0.33 to 13 ± 2 ps at XDMSO = 0.95. The water molecules forming hydrogen bonds to the C═O group of acetone show a much faster reorientation with a time constant that decreases from 6.1 ± 0.2 ps at Xacet = 0.3 to 2.96 ± 0.05 ps at Xacet = 0.9. The large difference in reorientation time constant of the solute-bound water for DMSO and acetone can be explained from the fact that the hydrogen bond between water and the S═O group of DMSO is much stronger than the hydrogen bond between water and the C═O group of acetone. We attribute the strongly different behavior of water in DMSO-rich and acetone-rich mixtures to their difference in molecular shape.

Picosecond solvation dynamics--a potential viewer of DMSO-water binary mixtures.

In this work, we have investigated the composition dependent anomalous behavior of dimethyl sulfoxide (DMSO)-water binary mixture by collecting the ultrafast solvent relaxation response around a well known solvation probe Coumarin 480 (C480) by using a femtosecond fluorescence up-conversion spectrometer. Recent molecular dynamics simulations have predicted two anomalous regions of DMSO-water binary mixture. Particularly, these studies encourage us to investigate the anomalies from experimental background. DMSO-water binary mixture has repeatedly given evidences of its dual anomalous nature in front of our systematic investigation through steady-state and time-resolved measurements. We have calculated average solvation times of C480 by two individual well-known methods, among them first one is spectral-reconstruction method and another one is single-wavelength measurement method. The results of both the methods roughly indicate that solvation time of C480 reaches maxima in the mole fraction of DMSO XD = 0.12-0.17 and XD = 0.27-0.35, respectively. Among them, the second region (XD = 0.27-0.35) is very common as most of the thermodynamic properties exhibit deviation in this range. Most probably, the anomalous solvation trend in this region is fully guided by the shear viscosity of the medium. However, the first region is the most interesting one. In this region due to formation of strongly hydrogen bonded 1DMSO:2H2O complexes, hydration around the probe C480 decreases, as a result of which solvation time increases.

Elucidation of the Water–DMSO Mixing Process Based on an IR Study

The IR spectra of water–DMSO mixtures were recorded in the range of 0 < x < 1 DMSO mole fraction in the spectral region of 400–6000 cm−1. The combination and libration bands of water and the S = O band of DMSO were used to monitor changes in the system. The combination and libration bands of water were analyzed in terms of different degrees of connectivity of water molecules. Two types of complexes differing by their water–DMSO ratio and the nature of water participating in their formation were found in the mixture. Complex I involves large water clusters stabilized by DMSO molecules and gradually diminishing in their size with increasing DMSO content. Water molecules separated from the bulk water interact with DMSO to form complex II. The water clusters were shown to exist in the mixture up to 90 mol% DMSO. The inertness of the inner molecules of the water cluster is the reason of the begining of DMSO accumulation at the notable water excess.

The local environment of the molecules in water–DMSO mixtures, as seen from computer simulations and Voronoi polyhedra analysis

Molecular dynamics simulations of water-DMSO mixtures, containing 10, 20, 30, 40, 50, 60, 70, 80, and 90 mol% DMSO, respectively, have been performed on the isothermal-isobaric (N,p,T) ensemble at T = 298 K and at the pressure equal to the experimental vapor pressure at each mixture composition. In addition, simulations of the two neat systems have also been performed for reference. The potential models used in the simulations are known to excellently reproduce the mixing properties of these compounds. The simulation results have been analyzed in detail by means of the Voronoi polyhedra (VP) of the molecules. Distributions of the VP volume and the asphericity parameter as well as that of the radius of the spherical intermolecular voids have been calculated. Detailed analyses of these distributions have revealed that both molecules prefer to be in an environment consisting of both types of molecules, but the affinity of DMSO for mixing with water is clearly stronger than that of water for mixing with DMSO. As a consequence, the dilution of the two neat liquids by the other component has been found to follow different mechanisms: when DMSO is added to neat water small domains of neat-like water persist up to the equimolar composition, whereas no such domains are found when neat DMSO is diluted by water. The observed behaviour is also in line with the fact that the main thermodynamic driving force behind the full miscibility of water and DMSO is the energy change accompanying their mixing, and that the entropy change accompanying this mixing is negative in systems of low and positive in systems of high DMSO mole fractions. Finally, we have found a direct evidence for the existence of strong hydrogen bonded complexes formed by one DMSO and two water molecules, but it has also been shown that these complexes are in equilibrium with single (monomeric) water and DMSO molecules in the mixed systems.

Synthesis of indoles, benzofurans, and related heterocycles via an acetylene-activated SNAr/intramolecular cyclization cascade sequence in water or DMSO.

The synthesis of 2-substituted indoles and benzofurans was achieved by nucleophilic aromatic substitution, followed by subsequent 5-endo-dig cyclization between the nucleophile and an ortho acetylene. The acetylene serves the dual role of the electron withdrawing group to activate the substrate for SNAr, and the C1-C2 carbon scaffold for the newly formed 5-membered heteroaromatic ring. This method allows for the bond forming sequence of Ar-X-N/O-C1 to proceed in a single synthetic step, furnishing indoles and benzofurans in moderate to high yields. Since the method is not transition metal mediated, brominated and chlorinated substrates are tolerated, and benzofuran formation can be conducted using water or water-DMSO mixtures as solvent.