Influence of the Coordination of Donor Solvent Molecules to 1,4,7,10-Tetramethyl-1,4,7,10- tetraazacyclododecanenickel(II) and Analogous Nickel(II) Complexes on Their Steric Factors

Coordination equilibrium constants (K _NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me₄[12]aneN₄)]²⁺) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K _NiS1) and second stepwise coordination equilibrium constants (K _NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN₄)]²⁺), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN₄)]²⁺), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS₄)]²⁺) were also reinvestigated. The K _NiS values for [Ni(Me₄[12]aneN₄)]²⁺ were compared to those of [Ni([12]aneN₄)]²⁺, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺), R,R,S,S-[Ni(Me₄[14]aneN₄)]²⁺, [Ni([14]aneN₄)]²⁺, and [Ni([14]aneS₄)]²⁺. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me₄[12]aneN₄)]²⁺ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺. The K _NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm³⋅mol⁻¹, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺, but such waters did not coordinate to [Ni(Me₄[12] aneN₄)]²⁺. Also, the K _NiS2 values were larger than the corresponding K _NiS1 values for [Ni([14]aneS₄)]²⁺. Furthermore, the K _NiS1 values for [Ni([12]aneN₄)]²⁺ were the largest among these nickel(II) complex cations. The K _NiS, K _NiS1, and K _NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations.     

Effect of solvent on glass transition temperature in chemically modified polyvinyl chloride (PVC)

Polyvinylchloride has been chemically modified with sodium benzene thiolate at different temperatures, in solvents promoting the formation of polymer gels, in solvents favoring light polymer interactions and in the absence of solvent, that is, in the melt. From the¹³C-NMR results it is shown that the substitution reactions on PVC, in all media and temperatures studied, are stereospecific and the nature of substituted chlorines the same.The glass transition temperature of modified polymers has been studied by differential scanning calorimetry. The glass transition temperature of the modified polymers in the absence of solvent decreases linearly with degree of substitution. When the reaction is carried out in solvents containing carbonyl groups, such as diethyl malonate, cyclohexanone and 2-butanone, the evolution of the glass transition up to about 25% substitution does not follow the above behavior. At higher levels of substitution the evolution ofT _g is similar to that in the melt. For the ether-containing solvents, such as tetrahydrofurane and dioxane, the evolution lies between the two previous curves.When the reactions of PVC with sodium benzene thiolate are carried out in cyclohexanone at different temperatures, between 15–90°C, the evolution of the glass transition temperature with conversion is different for each temperature, and if the reaction temperature increases, the slope of the initial part moves to that in the absence of solvent.These results are related to the formation of PVC gels or interactions. As the nature and percentage of substituted chlorine for a given chemical composition are the same in all the solvents and conditions studied, we propose that Cl-atoms of isotactic and/or heterotactic configurations are implied in the formation of PVC gels or interactions.     

Solubility of Tris-(hydroxymethyl)-aminomethane in water-2-methoxyethanol solvent mixtures and the solvent effect on the dissociation of the protonated base

Solvent effects are discussed in terms of the free energies of transfer G_t ⁰ from water to aqueous 2-methoxyethanol (MCS) solvents, of the uncharged base (B) evaluated from the measured solubilities, of HCl evaluated earlier, and of Tris hydrochloride (B.HCl). The characteristic minimum at 25°C is attributed to selective solvation of the individual species involved in the equilibrium process. The results indicate that the primary solvation either of H⁺ or BH⁺ ions arising from specific ion-dipole interactions outweigh the electrostatic or the secondary solvation effect.     

溶剂对氟烷基卤代烷^1^9FNMR 化学位移的影响

长期以来,溶剂对反应途径和反应物的影响及他们之间的关系是物理和有机化学家一个十分感兴趣的课题。溶剂影响氟烷基碘的~(19)F NMR 曾有文献报道。我们在研究氟烷基碘与铜反应中的溶剂作用时,发现,在配位能力较小的溶剂中反应经自由基中间体,而在配位能力较大的溶剂中反应是通过氟烷基铜中     

系统研究溶剂和温度对形成三种钴簇基金属-有机框架化合物的影响：结构和气体吸附性质

通过调控DMSO/DMF/H2O混合溶剂中溶剂成分的物质的量比和反应温度,合成出3种基于1,3,5-三(4′-羧甲基苯基)苯(H3BTB)和氯化钴的钴簇基金属-有机框架化合物(NH2Me2)2[Co3O(BTB)2(H2O)].2H2O.4.5DMF.7.5DMSO(1),(NH2Me2)2[Co4O(BTB)8/3].6H2O.13DMSO(2)和(NH2Me2)2[Co6O3(BTB)8/3(H2O)4].5H2O.5DMF.13DMSO(3),它们分别含有三核Co3O簇、四核Co4O簇和六核Co6O3簇。这种六核簇为我们首次发现。研究表明,相对中等的温度105℃和较多DMF的使用有利于三核簇的形成;125℃高温和溶剂DMSO有利于四核簇的构建;与形成1的条件相比,较低的温度95℃和更多水的存在则有利于六核簇的生成。2和3虽然由不同的金属簇构成,但具有相同的框架结构,Schlfli符号为(43)8(48.64.812.104)3。此外,还研究了2和3抽出溶剂后产物的气体吸附性质,它们均具有较高的氢气吸附焓。     

The Solvent Effect on Composition and Dimensionality of Mercury(II) Complexes with Picolinic Acid

Three new mercury(II) coordination compounds, {[HgCl(pic)]}_n (1), [HgCl(pic)(picH)] (2), and [HgBr(pic)(picH)] (3) (picH = pyridine-2-carboxylic acid, picolinic acid) were prepared by reactions of the corresponding mercury(II) halides and picolinic acid in an aqueous (1) or alcohol–methanol or ethanol (2 and 3) solutions. Two different types of coordination compounds were obtained depending on the solvent used. The crystal structures were determined by the single-crystal X-ray structural analysis. Compound 1 is a one-dimensional (1-D) coordination polymer with mercury(II) ions bridged by chelating and bridging N,O,O′-picolinate ions. Each mercury(II) ion is four-coordinated with a bidentate picolinate ion, a carboxylate O atom from the symmetry-related picolinate ion and with a chloride ion; the resulting coordination environment can be described as a highly distorted tetrahedron. Compounds 2 and 3 are isostructural mononuclear coordination compounds, each mercury(II) ion being coordinated with the respective halide ion, N,O-bidentate picolinate ion, and N,O-bidentate picolinic acid in a highly distorted square-pyramidal coordination environment. Compounds 1–3 were characterized by IR spectroscopy, PXRD, and thermal methods (TGA/DSC) in the solid state and by ¹H and ¹³C NMR spectroscopy in the DMSO solution.     

Degradation of a poly(ester urethane) elastomer. I. Absorption and diffusion of water in Estane® 5703 and related polymers

In preparation for studying the hydrolytic degradation of Estane® 5703 and related poly(ester urethane) elastomers, the absorption (solubility) and diffusion of water in these polymers have been examined experimentally and modeled theoretically. Weight gain and loss experiments have been carried out. The amount of water absorbed per gram of sample was linear at low relative humidities (RHs) but curved upward at higher RHs. This curvature was not fit by Henry's law or the Flory–Huggins equation but was easily fit by a water‐cluster model. Diffusion coefficients were determined by fitting the time dependence of the sample weights, and the diffusion appeared Fickian to within experimental uncertainty. The similarity of related polymers was used to determine the approximate temperature dependence of the absorption. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 181–191, 2002     

Solvent effects on complexation of thallium(I) with guanosine 5′‐monophosphate in methanol–water mixtures

The interaction of guanosine 5′‐monophosphate, GMP, with the thallium(I) ion was studied by UV–vis and potentiometric titration methods and ³¹P NMR spectroscopy. Both NMR spectra and UV–vis titration data have shown that GMP coordinates via guanine to the thallium(I) ion in the pH range 1.5–10. Our study of the system Tl(I) + GMP was performed in water–methanol mixtures with different volume ratios of methanol. The complexation equilibrium in the pH range of study led to the following mononuclear species: TlH₂(GMP)⁺, TlH(GMP) and Tl(GMP)^?, where (GMP)^2? represents the fully dissociated ligand. The formation constants of the species were calculated in the various media at constant temperature (25 °C) and constant ionic strength of sodium perchlorate (0.1 mol dm^?3) using a suitable computer program. The formation constants were analyzed in terms of Kamlet and Taft's parameters. A single‐parameter correlation of the formation constants, β₁₂₁, β₁₁₁ and β₁₀₁ vs α (hydrogen‐bond donor acidity), β (hydrogen‐bond acceptor basicity) and for π* (dipolarity/polarizability) are relatively poor in all solutions, but multi‐parameter correlations represent significant improvements with regard to the single‐parameter model. In this work, we have also used the normalized polarity parameter, E_T^N, alone and in combination with some of the Kamlet–Taft parameters to find a better correlation of the formation constants in different methanol–water mixtures. Copyright © 2007 John Wiley & Sons, Ltd.     

Solvation of amides of formic and acetic acids in water-glycerol mixture. Additivity of thermochemical characteristics of solutions

Values of the solution enthalpy of are measured and values of solvation enthalpy are calculated for formamide and N,N-two-substituted methyl-and ethylamides of formic and acetic acids in the mixed solvent: water-glycerol. Enthalpy coefficients of pair interactions between amides and glycerol in aqueous solutions are calculated. The influence of mixture composition and also of a structure and properties of the dissolved compounds on enthalpy characteristics is considered. Within the frames of the offered additive scheme the contributions from the structural fragments of molecules of amides to enthalpy characteristics of solutions are established. It has allowed us to analyze quantitatively the role of nonspecific and specific solvation of amides in solution, to predict the enthalpy of evaporation, solution, solvation, the enthalpy coefficients of pair interactions of experimentally unstudied N-methylformamide, N-ethylformamide, N-methyl-N-ethylformamide, N-methylacetamide, N-ethylacetamide, and N-methyl-N-ethylacetamide in the mixtures of water-glycerol, and also to evaluate the donor numbers of these specified amides.     

Effect of Solvent and Acid‐Base on Palladium (II)‐catalyzed Dicarbonylation of Terminal Acetylenes: a General,Efficient and Stereoselective Synthesis of Maleic Diesters and Maleic Anhydrides

The productions of maleic diesters and maleic anhydrides depend on the effect of solvent and acid‐base in palladium‐catalyzed dicarbonylation of terminal acetylenes. For primary and secondary alcohol in benzene, only maleic diesters were obtained stereospecifically from the dicarbonylation of acetylenes in the presence of PdCl₂, CuCl₂, and NaHCO₃. For tertiary alcohols, maleic anhydrides were synthesized selectively.     

Studies on Ultrasonic Degradation and Block Copolymerization of Hydroxyethylcellulose and Poly(ethylene Oxide)

The ultrasonic degradation of hydroxyethylcellulose (HEC) and poly (ethylene oxide) (PEO) in aqueous solution, and the copolymerization of HEC with PEO were studied. The structure of the copolymer was identified by DTA, IR, MS, x-ray diffraction, and polarizing microscopy. The copolymer prepared is mainly block. The copolymer formed amounts to 55.07% by irradiating 0.5% HEC/PEO aqueous solution for a period of 10 min at 25°C and 18.2 kHz with 2.5 A input current on a reversed main circuit.     

Solvent Effects on the UV (n → π*) and NMR (17O) Spectra of Acetone in Aqueous Solution: Development and Validation of a Modified AMBER Force Field for an Integrated MD/DFT/PCM Approach

A modified AMBER force field has been developed and used to compute UV and NMR spectra of acetone in aqueous solution by an integrated computational tool rooted in the density functional theory, the polarizable continuum model, and classical molecular dynamics. The results show that, provided that classical force fields are carefully reparameterized and validated, they can be part of a robust and effective approach, which can be used also by non-specialists and provides a general and powerful complement to experimental techniques.     

Surface‐Initiated Atom Transfer Radical Polymerization of Oligo(ethylene glycol) Methacrylate: Effect of Solvent on Graft Density

Summary: Oligo(ethylene glycol) methacrylate (OEGMA) was grafted from silicon wafer surfaces by surface‐initiated atom transfer radical polymerization (ATRP) with Cu^I Br/2,2′‐bipyridine (bpy) as a catalyst and various water/alcohol mixtures as solvents. The ellipsometric thickness of the poly(OEGMA) layer on the surface increased linearly with monomer conversion in solution. High graft densities were achieved in alcohols. The graft density of poly(OEGMA) in methanol was found to be 0.26 chains · nm⁻², which is 50% higher than that in water/methanol (30:70, v/v). The differences in graft density were correlated to the conformation of tethered poly(OEGMA) chains. Large poly(OEGMA) coils on the surface in the presence of water limited the access of initiation sites to the catalyst complex and monomer molecules.

Development of poly(OEGMA) layer thickness on the silicon surface vs monomer conversion.     

Effect of poly(ethylene glycol) 200 on the formation of a polyetherimide asymmetric membrane and its performance in aqueous solvent mixture permeation

To investigate the effect of poly(ethylene glycol) (PEG) 200 on membrane performance, asymmetric polyetherimide (PEI) membranes with a small pore size were prepared by dry/wet-phase inversion from the casting solution containing N-methyl-2-pyrrolidone as a solvent and poly(ethylene glycol) 200 as an additive. Our experiment revealed that the addition of PEG 200 has an influence on the casting solution properties, permeation properties, and resulting membrane structures. Moreover, a drying process also affects the formation of a dense skin layer. Increasing the amount of PEG 200 drastically improved the solute rejection rate. The drying process improved the rejection rate. We also observed the effect of the mixed solvent (water/ethanol) on permeation through the membranes with various pore sizes. In the case of the membrane with a dense skin layer, the solvent permeation showed relationships with solution viscosity, surface tension, and membrane-solvent interaction.     

Studies on silver(I) solvation in binary solvent mixtures containing dimethylsulfoxide. IV determination of solvent transference numbers for AgSCN and ionic coordination numbers of Ag+ in methanol-dimethylsulfoxide mixtures at 25°C

Solvent transport by AgSCN in the methanol (M)+dimethylsulfoxide (DMSO) system has been studied at 25°C by e.m.f. measurements. The solvent transference number of DMSO is positive as its concentration increases in the cathode compartment during electrolysis. The solubility of AgSCN has been determined in methanol, in DMSO and in methanol-DMSO mixtures. Using the known Gibbs free energy of solvation for the Ag⁺ ion, the corresponding energy for SCN, was found to be independent of the mole fraction. The experimental solvent transference numbers therefore only represent the contribution of Ag⁺, this is because it is preferentially solvated by DMSO. A coordination model has been applied to the Gibbs free energy of transfer of Ag⁺ in order to obtain coordination numbers thereby allowing calculation of solvent transference numbers. The experimental and the calculated solvent transference numbers are in good agreement at mole fractions of DMSO greater than 0.5. In highly methanolic solutions the assumption that the solvation of Ag⁺ in the solvent system studied is adequately represented by a total coordination number of four, proves to be too simple.     

Effect of poly(ethylene oxide) on the structure and properties of poly(vinyl alcohol)

To improve the drawability of poly(vinyl alcohol) (PVA) thermal products, poly(ethylene oxide) (PEO), a special resin with good flexibility, excellent lubricity, and compatibility with many resins, was applied, and the Fourier transform infrared spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WXRD) were adopted to study the hydrogen bonds, water states, thermal properties, crystal structure, and nonisothermal crystallization of modified PVA. It was found that PEO formed strong hydrogen bonds with water and PVA, thus weakened the intra‐ and inter‐hydrogen bonds of PVA, changed the aggregation states of PVA chains, and decreased its melting point and crystallinity. Moreover, the interactions among PVA, water, and PEO retarded the water evaporation and made more water remain in the system to plasticize PVA. The existence of PEO also slowed down the melt crystallization process of PVA, however, increased the nucleation points of system, thus made more and smaller spherulites formed. The weakened crystallization capability of PVA and the lubrication of PEO made PVA chains to have more mobility under the outside force and obtain high mechanical properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1946–1954, 2010     

Solvent Effect on the Assembly of Two Cadmium(II) Coordination Polymers Derived from 3,3′‐(Diazenediyl)dibenzoic Acid: Syntheses,Structures, Stabilities,and Photocatalytic Properties

Abstract. Two cadmium(II) coordination polymers, {CdL₂[(CH₃)₂NH₂]₂ · 2DMF}_n ( 1 ) and {[Cd₃L₄[(CH₃)₂NH₂]₂] · EtOH · 2DMF}_n ( 2 ) were synthesized from the solvothermal reactions of Cd(OAc)₂ · 2H₂O with 3,3′‐(diazenediyl)dibenzoic acid (H₂L) in different solvents. Both complexes were characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction, TG analysis, and single‐crystal X‐ray diffraction. In compound 1 , central cadmium(II) atoms were linked with the surrounding L ligands to generate an infinite 1D chain with repeated rings. Compound 2 displayed a 3D threefold interpenetrating framework based on cage‐like [Cd₃L₆]₈ species and exhibited a 4¹²6³ topological structure. The results demonstrated that the different solvents had significant effect on the construction of different coordination compounds from the same components. In addition, they exhibited excellent stability and good photocatalytic activity towards the degradation of methylene blue in aqueous solution under UV irradiation.     

Theoretical Study on Thermodynamic Properties and Hydrophilicity of Polychorinated Phenothiazines （PCPTZs）

The thermodynamic properties of 135 polychlorinated phenothiazines (PCPTZs) in the standard state are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G** level, and their octanol-water partition coefficients (logKow) are calculated based on group contributions. The chlorine substitution pattern strongly influenced the thermodynamic properties and hydrophilicity of the compounds. The thermodynamic properties of congeners also depend on the chlorine substitution pattern. The effect of chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution (NPCS). The results show that the NPCS model may be used to predict the thermodynamic properties and hydrophilicity for all 135 PCPTZ congeners.