Dioxane Mixtures Research Articles

Concentration Fluctuation/Microheterogeneity Duality Illustrated with Aqueous 1,4-Dioxane Mixtures.

The structural properties of aqueous 1-4 dioxane mixtures are studied by computer simulations of different water and dioxane force field models, from the perspective of illustrating the link between structural properties at the molecular level and measurable properties such as radiation scattering intensities and Kirkwood-Buff integrals (KBIs). A strategy to consistently correct the KBI obtained from simulations is proposed, which allows us to obtain the genuine KBI corresponding to a given pair of molecular species, in the entire concentration range, and without necessitating excessively large system sizes. The application of this method to the aqueous dioxane mixtures, with an all-atom CHARMM dioxane model and 2 water models, namely, SPC/E and TIP3P, allows one to understand the differences in the structure of the corresponding mixtures at the molecular level, particularly concerning the role of the water aggregates and its model dependence. This study allows us to characterize the dual role played by the concentration fluctuations and the domain segregation, particularly in what concerns the calculated X-ray spectra.

Structurally Diverse Pyrene-decorated Planar Chiral [2,2]Paracyclophanes with Tunable Circularly Polarized Luminescence between Monomer and Excimer.

We reported the synthesis of a series of structurally diverse CPL-active molecules, in which pyrene units were installed to chiral pm/po-[2,2]PCP scaffolds either with or without a triple bond spacer for pm/po-PCP-P1 and pm/po-PCP-P2, respectively. The X-ray crystallographic analyses revealed that these pyrene-based [2,2]PCP derivatives exhibited diverse structures and crystal packings in the solid phases. The pyrene-based [2,2]PCP derivatives exhibit various (chir)optical properties in organic solutions, depending on their respective structures. In a mixture of dioxane and water, pm/po-PCP-P1 emit green excimer fluorescence, whereas pm/po-PCP-P2 emit blue one. The chiroptical investigation demonstrated that Rp-pm-PCP-P1 and Rp-pm-PCP-P2 exhibited completely opposite CD and CPL signals even they possess the same chiral Rp-[2,2]PCP core. The same argument also holds for other chiral pyrene-based [2,2]PCP derivatives. The theoretical calculation revealed that these unusual phenomena were attributed to different orientation between transition electric dipole moments and the magnetic dipole moments originating from the presence or absence of a triple bond spacer. These pyrene-based [2,2]PCP derivatives display various colours and fluorescence emissions in the solid state and PMMA films, possibly due to the different packings as observed in the crystal structure. Moreover, these compounds also can interact with perylene diimide through π-π interactions, leading to near-white fluorescence.

Construction and catalytic effects of solvent- and metal(ii)-dependent products: the process of transformation of 0D structures into 3D structures

The dimensions of M(ii) complexes are dependent on the solvents or metals(ii) employed, and a transformation of the cage into 3D occurs. Zn(ii) and Cu(ii) species are effective catalysts in transesterification and catechol oxidation, respectively.

The non-ideality in binary aqueous systems contributed to the different abilities of solvent entities incorporated in the solvation shell of methylene blue

The solvatochromic properties of methylene blue (MB) were investigated in neat water, methanol, ethanol, propanol, dioxane and their corresponding aqueous mixtures. The correlation of the empirical solvent polarity scale (ET) values of MB with solvent composition was analysed using the solvent exchange model of Bosch and Roses to explain the preferential solvation of the probe thiazine dye in the binary mixed solvents. Non-linear solvatochromism of MB was observed in aqueous mixtures of methanol, ethanol, propanol and dioxane. The influence of the composition of the solvating shell in preferential solvation of the solute dye was investigated in terms of both solvent?solvent and solute?solvent interactions, and the local mole fraction of each solvent composition in the cybotactic region of the probe was also calculated. Effective mole fraction variation can provide important physicochemical insights into the microscopic and molecular interactions between MB species and solvent components. The results showed that the MB solvation shell was thoroughly saturated with the solvent complex S12 for dioxane more than ethanol and propanol mixtures, and opposite trends for methanol mixtures, whereas the solvent complex S12 could not incorporate into the MB solvation shell. Data from the binary systems were analysed with KAT parameters using a dual model of basicity and polarity. The results showed that the polarity was better suited for spectral shift in aqueous methanol and ethanol solutions, while the basicity was better for aqueous propanol and dioxane solutions.

Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) Monoliths by Spinodal Decomposition for Hydrodynamic Chromatography

Porous materials with low tortuosities are needed when efficient liquid transport through a substrate is required. Thus, the development of materials with homogeneous interconnected pores can improve the performance of porous supports for flow-through applications. In this paper, the synthesis of a poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) monolith by spinodal decomposition is reported. The obtainment of experimental conditions for phase separation by spinodal decomposition was achieved by using a reversible addition–fragmentation chain transfer (RAFT) polymerization mechanism for the synthesis of porous monoliths. Moreover, the chemical nature and composition of the porogen mixture were found to be key factors in the porous structure of the resulting materials. Mixtures of poly(tert-butyl methacrylate) and dioxane were used as porogens for the obtainment of monoliths by spinodal decomposition, and the composition of the porogen mixture allowed control over their pore size. The obtained methacrylate monoliths were used as stationary phases for hydrodynamic chromatography and allowed size-based separations of high-molar-mass polymer standards.

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Solvent Effect on Photo / Thermo Responsive behaviour and Application of Poly(N-isopropylacrylamide) End-capped with 4-Propoxyazobenzene in Aqueous Media

ABSTRACT The photoisomerisation behaviour of Poly(N-isopropylacrylamide) end-capped with 4-propoxyazobenzene (PNIPAM-Azo-OC3H7) was studied in a conconsolvent mixture of water and dioxane. The trans-cis isomerisation rate of PNIPAM-Azo-OC3H7 was mildly affected by the solvent compositions. Interestingly, the addition of dioxane could not only change the lower critical solution temperature (LCST) of PNIPAM-Azo-OC3H7 aqueous solution but also accurately controlled the increase or decrease in the LCST during UV irradiation. The LCST change (ΔT) could be adjusted from −5.0°C to 10.0°C, which was affected by the cononsolvent type, the second solvent and polymer concentration. Transmission electron micrographs (TEMs) showed that the PNIPAM-Azo-OC3H7 solution could self-assemble into different nano-micelles in different amounts of miscible solvents. UV irradiation of PNIPAM-Azo-OC3H7 solution was found to induce different changes in particle shape and size, which in turn led to either decrease or increase in the LCST changes in this novel responsive system. Furthermore, Nile red was tested here as a fluorescence probe for photo-induced release from PNIPAM-Azo-OC3H7 micelles, and the results suggested that this polymer could be used as a hydrophobic chemotherapeutic drug carrier for controlled release.

Deciphering the Interaction of a Macrocyclic Tetranuclear Zn(II) complex with Biomimicking Surfactant: A Case Study using Cetyltrimethylammonium Bromide

The detection of various biologically important cationic and anionic species has led to the synthesis of various Zinc (II) Schiff base complexes, which bear a large application in catalysis and sensors. A recently reported study has indicated a synthesis of a 48 membered macrocyclic Zn(II) Schiff base complex, which functions as a dual anion sensor (DAS) containing a protonated amine group. In the present investigation, an attempt has been made to study the interaction of the Zn tetranuclear complex (Zn-TCom), a neutral complex, with a cationic surfactant cetyltrimethylammonium bromide (CTAB), employing steady-state absorption and fluorescence studies. The change in the photophysical properties of the fluorophore is studied on binding with the surfactant. The steady-state absorption and emission studies reveal that the polarity of the surrounding of the fluorophore has been modified upon binding with CTAB. A study on the alteration of polarity during the interaction of Zn-TCom with the surfactant is studied by comparing the fluorescence behavior of the probes in a micro heterogeneous environment in a mixture of dioxane and water of varying composition. The binding constant magnitude (analyzed using the Hildebrand equation) manifests that the Schiff base binds to the micellar compartment. These results are manifested to enhance the potential application of the macrocyclic complex in the field of biochemistry. Furthermore, quantum chemical calculations are undertaken to correlate the molecular structure of Zn-TCom with the associated frontier molecular orbitals. The parameters like the energy of HOMO, LUMO and the associated Mulliken charges with respect to individual elements are computed using the single point geometry. The studied reports are correlated with the feasibility of binding with bio mimicking environment or bio proteins for selective application as drug carriers.

Probing the binding interaction of zinc (II) Schiff bases with bovine serum albumin: A spectroscopic and molecular docking study

Entrapping of potent Schiff base with biomimetic environment using fluorescence properties enables better understanding of their interaction for drug‐based application. A detailed photophysical study of zinc (II) Schiff bases, 2,6‐bis((E)‐((2‐(dimethylamino) ethyl)imino)methyl)‐4‐R‐phenol, where R = methyl/tertiary butyl/chloro is reported by utilizing bovine serum albumin (BSA) as the bio membrane. Steady state absorption and emission studies of Schiff base‐protein system have been found to get altered by change in the compartmental ligand. Alternation of polarity caused by such compartmental ligands is reported by comparing the fluorescence behavior of the probes in microheterogeneous environment in a mixture of dioxane and water of varying composition. Hildebrand equation accounts for negative binding constants among BSA with Schiff base with Cl (‐I) group as the compartmental ligand in contrast to the positive magnitudes with ligands exhibiting +I effect. Functionality of such compartmental ligands (intra interactions studied using Hirshfeld analyses) upon binding with the protein is also studied in terms of quenching and denaturation studies. Schiff base with Me is found to be the most favorable ligand that bound to BSA as corroborated from the binding, quenching, micropolarity, and docking studies. Molecular docking studies predict the affinity energies for suitable binding conformations to be ~ − 6 kcal mol−1 for BSA‐Schiff base (with Me ligand).

Transformations of Cobalt(II) Trifluoroacetates in 1,4-Dioxane: Solvent Effect on the Composition, Structure, and Crystal Packing of the Molecules

The reaction of aqueous cobalt(II) acetate with trifluoroacetic acid in methanol affords complex [Co(OOCF3)2(OH2)4] (I). The same reaction in a methanol–benzene–dioxane mixture of solvents gives mononuclear complex [Co(OOCF3)2(OH2)6] ∙ O(CH2CH2)2O (II) in which the solvate dioxane molecule forms a single crystal by the formation of hydrogen bonds with coordinated water molecules. A similar reaction in pure dioxane affords trinuclear complex {Co3(OOСCF3)4(OH2)2(OOСCF3)2[O(CH2CH2)2O]2} ∙ 2HOOСCF3 ∙ 2O(CH2CH2)2O (III) containing both solvate and coordinated dioxane molecules. The crystallization of complex III from an isopropanol–dioxane mixture leads to complex [Co(OOСCF3)2(OH2)4] ∙ 2O(CH2CH2)2O (IV). The reaction of complex III with pyrazole (HРz) affords mononuclear complex [Co(OOСCF3)2(HРz)4] ∙ 2O(CH2CH2)2O (V). The reaction of complex I with HРz in methylene dichloride leads to mononuclear complex [Co(OOСCF3)2(HРz)4] (VI). The structures of coordination compounds I–VI are determined by X-ray diffraction analysis (СIF files CCDC nos. 1985667 (I), 1985666 (II), 1985671 (III), 1985670 (IV), 1985665 (V), and 1985669 (VI) at Т = 296(2) K and 1985668 (VI) at Т = 150(2) K).

Thermochemical investigation of L-glutamine dissolution processes in aqueous co-solvent mixtures of acetonitrile, dioxane, acetone and dimethyl sulfoxide at T = 298.15 K

This article reports on the results of calorimetric studies of the processes of L-glutamine dissolution in some aqueous-organic mixtures, namely (H2O + acetonitrile), (H2O + 1,4-dioxane), (H2O + acetone) and (H2O + dimethyl sulfoxide) at T = 298.15 K and mole fractions of an organic solvent up to x2 ~ 0.25. The standard values of solution (ΔsolH°) and transfer (ΔtrH°) enthalpies of L-glutamine from water to a mixed solvent as well as the enthalpic coefficients of pair-wise interactions (hxy) were calculated. The interrelation between enthalpic characteristics of L-glutamine dissolution (transfer) and the composition of water-organic mixtures was determined. It is found that the values of hxy are correlated with some physicochemical properties of different organic solvents. Contributions of the organic solvent properties (molar volume, cohesion energy density, polarity/polarizability, acidity, and basicity) to the energy of pair-wise interactions of L-glutamine - organic solvent were estimated quantitatively using of a modified Kamlet-Taft equation. The parameters of pair-wise interactions were additionally used to assess the contributions of the side chains of several L-amino acids to the energy of the intermolecular interactions amino acid-organic co-solvent in aqueous solutions.

Fluorescence of Naphthol AS-MX is Readily Detectable in Dioxane Mixtures

Fluorescence of Naphthol AS-MX is Readily Detectable in Dioxane Mixtures

Features of complex formation of a fibrous complexite with nickel ions in water–dioxane mixtures

The study deals with the complex-forming properties of a fibrous complexing agent (complexite) NAG with respect to nickel(II) ions in a mixed solvent water-1,4-dioxane. Spectral tests indicate that the absorption of nickel(II) ions by the NAG fibrous complexer occurs according to the mechanism of complexation. The factors affecting the complex formation of the NAG complexite with nickel(II) ions in water-1,4-dioxane mixtures are established, and the stability constants of hydroxamic and amidoxime groups are calculated depending on the pH values of the medium and the composition of the solvent. The influence of the solvation parameter on the composition and stability of the complexes under study with nickel(II) ions has been established. The solvation characteristics of the NAG complexite and complexes with nickel(II) ions depend on the nature of the mixed solvent in which the complexation reaction takes place. The solvation effects in the water-1,4-dioxane mixture with a molar fraction of dioxane of 0.00–0.17 level the stability of the resulting complexes. It is shown that the pH range of 6.2–3.8 mixed solvent creates the conditions for the formation of a wider composition and structure of the range of coordination units with different proportions of their content in the polymer. Apart from the hydroxamic, deprotonated amidoxime groups take part in the complexation. The preferred fixation of functional groups on the surface of NAG fibres leads to a high local concentration of the reaction centres and enhances the cooperativeness of the process, facilitating easy orientation of the groups during the formation of mixed-ligand coordination nodes. The stability constants of the deprotonated amidoxime groups of the the NAG complexite with nickel(II) ions are estimated. The study has proved dependence on the composition of the solvent

Influence of solvent, electrolytes, β-CD, OTAB on the krafft temperature and aggregation of sodium tetradecyl sulfate

The krafft temperature (Tk) of sodium tetradecyl sulfate (STS) has been determined conductometrically in aqueous, different aquo-organic solvent media (dioxane, formamide, and ethylene glycol), different concentrations of additives viz. NaCl, β-CD, and octadecyltrimethylammonium bromide (OTAB). The change in Tk in different media has been notified and summarized in tabular form. The micellar properties of STS also have been determined in binary aqueous mixtures of dioxane (DO) and formamide (FA) by tensiometry, conductometry and isothermal titration calorimetry. Different interfacial parameters, Gibbs surface excess (Γmax), area minima per surfactant (Amin), surface pressure (ΠCMC), and packing parameter (P) have been calculated from related well-known equations. Thermodynamic parameters, such as free energy for micellization (ΔGm0), free energy of adsorption (ΔGads0), change in enthalpy (ΔHm0), and entropy change associated with micellization (ΔSm0) have been also deduced. Aggregation number and Stern Volmer constant of STS in DO and FA have been determined from steady state fluorescence quenching study using fluorimetric technique.

Thermodynamic and kinetic studies on interaction of some transition metal ions with tryptophan

Amino acid of tryptophan (Trp) was chosen as a drug. A systematic approach was made to study its interaction with some transition metal ions, and qualitatively and quantitatively examine the thermodynamic and kinetic phenomena on this model drug. To accomplish these tasks, the stability constants of Trp complexes with Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) at temperatures of 25, 30, 35, and 40 °C were determined potentiometrically, utilizing modified Bjerrum’s method. Potentiometric titrations were carried out in water, and water:dioxane mixture (50:50, v : v ). Our findings showed that the stability constants of the complexes increased as the dioxane content was raised or temperature was elevated. The negative values of Δ G ° are indication of spontaneity of the processes. Δ H ° values are positive, conveying the complex formation is an endothermic process and Δ S ° values are positive contributing more to spontaneity, causing reaction favoring and disordering. The variations of natural logarithm of the stability constants versus 1/T are linear leading to evaluation of the stability constant of the complexes at any temperature. Moreover, kinetic study gave rise to estimation of rate constant and activation energy for each complex formation process. It was concluded that the order of increasing stability of the complexes is: k f Co(II) -Trp » k f Zn(II)- Trp < k f Pb(II) -Trp < k f Ni(II) -Trp < k f Cu(II) -Trp < k f Fe (III) - Trp . Furthermore the activation energy values for the aforementioned complexes in water-dioxane mixture obeyed the following trend E a Zn(II)-trp < E a Fe(III)-Trp < E a Ni(II)-trp < E a Co(II)-trp < E a Cu(II)-trp < E a Pb(II)-trp .

Enthalpy-entropy compensation effect and other aspects of isoparametricity in reactions between trans-2,3-bis(3-bromo-5-nitrophenyl)oxirane and arenesulfonic acids

It was found that as a result of the non-additivity (interaction) of joint effects of structure and temperature on the rate and free energy of activation of the reactions between trans-2,3-bis(3-bromo-5-nitrophenyl)oxirane and Y-substituted arenesulfonic acids YC6H4SO3H in a mixture of dioxane with 1,2-dichloroethane (7 : 3/v : v) at 265, 281, and 298 K, the cross reaction series exhibits isoparametric properties. At a temperature of 265 K, close to the isoparametric temperature point 262 K (isokinetic temperature), the free energy of activation and the rate of oxirane ring opening process do not depend on the structure of the substituent Y due to the enthalpy-entropy compensation effect. At the isoparametric point with respect to the constant of substituent Y (σY = 0.20), the free activation energy does not depend on temperature.

Synthesis, physical and chemical properties of 7-methylxanthine derivatives

It is known that 8-aminosubstituted N-methylated xanthines are dipeptidyl peptidase-4 antagonists, ligands for 5-hydroxytryptamine receptors and exert diverse biological effects. Previously, it was found that the 7-alkyl-8-piperazinoxanthines exhibit diuretic, depremic, analgesic effect. Some amino derivatives of 7-metilxanthine are promising antioxidants and 8-amino-7-ethyl-3-methylxanthine detects a distinct hypoglycemic effect. The aim of this work is to provide new derivatives of 7-methylxanthine – promising bioactive compounds and to study their physical and chemical properties as a basis for further structural modification of the molecule. Materials and methods . The melting point has been determined with the help of an open capillary method with PTP-M device. Elemental analysis has been performed with the help of the instrument Elementar Vario L cube, NMR-spectra have been taken on a spectrometer Bruker SF-400 (operating frequency of 400 MHz, solvent DMSO, internal standard – TMS). Results . It is established that the heating the source of bromxantine with an excess of primary amines in a mixture of water and dioxane leads to the formation of the corresponding 8-aminosubstituted 7-ethyl-3-methylxanthine. The reaction of 8-bromo-7-ethyl-3-methylxanthine and 8-bromo-7-ethyltheophylline with the more nucleophilic N-substituted piperazine is performed in the same conditions, but requires much less time and is accompanied by the formation of the corresponding 8-N-piperazinxanthines. Taking into account the amphoteric properties of imidazole it was possible to obtain 7-ethyl-8-(midazol-1)-3-methylxanthine through the reaction in dimethylformamide in the presence of equimolar amount of NaHCO 3 . 8-(4-Tret- butoxycarbonylaminopiperidinyl-1)-7-ethyl-3-methylxanthine and 8-(4-tret-butoxycarbonylamino-1)-7-ethyltheophylline are obtained by heating equimolar amounts of original bromxanthines, 4-tret-butoxycarbonylaminopiperidine and NaHCO 3 . The structure of the synthesized compounds is unambiguously proved by the method of NMR spectroscopy. The synthesized compounds are white crystalline substances soluble in hot alcohols, dioxane, DMF. The fact that 8-N,N-diethylamino-7-ethyl-3-methylxanthine and 7-ethyl-8-(midazol-1)-3-methylxanthine are well soluble in diluted acid solutions, can be used to obtain new bioactive salts with organic and inorganic acids. The presence of free N 1 H group enables the synthesis of new 1,3,7,8-tetrasubstituted of xanthine by the introduction of a variety of electrophilic reagents into the position of 1 uracil part of the molecule. Conclusions . Simply implemented methods for the synthesis of 8-amino-7-methylxanthine are developed. NMR-spectroscopic study of the obtained compounds, which clearly confirms their structure, is conducted. The prospective of the synthesized compounds for subsequent modification of their structure is demonstrated.

Simple computing of the viscosity of water-dioxane mixtures, according to a fluctuating SPC/E-Ih interstitial model.

In this contribution, we propose a new simple and fast computing approach to model liquid water and water-1,4 dioxane mixture, which is intermediate between molecular dynamics calculation and lattice fluid H-bonding theory in which water molecules are arranged according to a fluctuating hexagonal Ih network. It generalizes the interstitial mixture models of Samoilov and Pauling by increasing the number of spatial configurations into the space of phases due to the addition of rotations and vibrations of the molecules around their equilibrium positions. The potential energy landscape is determined by the generalization of the Madelung's approach to the molecular water network using simple point charge model (SPC/E partial charges). This approach allows useful predictions as the possibility of incorporation of a molecule of dioxane in the water Ih -network or how some cooperative dynamic jumps (site - hole) of water molecules, contribute to lower Eyring's activation energies and thus to facilitate the viscous flow. © 2017 Wiley Periodicals, Inc.

Influence of Tetra Alkyl Ammonium Cation and Temperature on Molecular Interactions Involves in Binary Liquid Mixtures of Dioxane and DMF at Various Temperatures

Influence of Tetra Alkyl Ammonium Cation and Temperature on Molecular Interactions Involves in Binary Liquid Mixtures of Dioxane and DMF at Various Temperatures

Compensation effect in reactions between trans-4,4'-dinitrostilbene oxide and arylsulfonic acids

The effect structure and temperature have on the rate and free activation energy of reactions between trans-4,4'-dinitrostilbene oxide and Y-substituted arylsulfonic acids YC6H4SO3H in a mixture of dioxane with 1,2-dichloroethane (7: 3 vol/vol) at 265, 281, and 298 K is studied. It is found that as a result of the nonadditivity of the joint effect of substituents Y and temperature on the rate of the process of oxirane ring opening, the cross reaction series exhibits isoparametric properties in the aspect of enthalpy–entropy compensation. This allows the experimental determination of an isoparametric point with respect to the constant of substituent Y (σYIP= 0.52), in which activation entropy ΔS≠ = 0 and free activation energy ΔG≠ do not depend on temperature (ΔG≠ = ΔH≠), and to conduct the transition through this point with inversion of the order of the effect temperature has on the value of ΔG≠ as a result of reversing the sign of ΔS≠: in the series Y (σY) = 4-OCH3 (–0.27), 4-CH3 (–0.17), H (0), 4-Cl (0.23), and 3-NO2 (0.71), the values of ΔS≠ (J/(mol K)) are–140,–119,–85,–42, and 44, respectively. The possibility of using isoparametric points as quantitative mechanistic criteria is demonstrated.