Octakis(dimethylammonium) hexa‐μ2‐chlorido‐hexachloridotrinickelate(II) dichloride: a linear trinickel complex with asymmetric bridging

The title compound, (C₂H₈N)₈[Ni₃Cl₁₂]Cl₂, crystallizes as linear [Ni₃Cl₁₂]⁶⁻ complex anions with inversion symmetry, separated from one another by dimethylammonium cations and noncoordinated chloride ions. The gross structural arrangement of the trinickel complex is as a segment of face‐sharing NiCl₆ octahedra similar to the (NiCl₃)_n chains of CsNiCl₃‐type compounds. On closer inspection, the regular coordination geometry of the complex consists of octahedral NiCl₆ in the center linked by two symmetrically bridging chloride ions to square‐pyramidal NiCl₅ on each end. A long semicoordinate bond is formed by each of the terminal Ni^II cations, to give a 5+1 coordination geometry and form an asymmetric bridge to the central Ni^II cation. The dimethylammonium cations surround the complex with an extensive hydrogen‐bonding network, linking the complex to the noncoordinated chloride ions. Asymmetric bridging in the complex arises from short hydrogen bonds from the same dimethylammonium cation to the apical and asymmetric bridging chloride ions, causing the complex to scissor outward.     

Surfactant effect on enhancing (S)-naproxen prodrug production from racemic naproxen by lipase

In the enantioselective esterification of racemic naproxen with 4(2-hydroxyethyl) morpholine by Lipase MY in organic solvents, a productivity improvement of the desired (S)-naproxen ester from 0.42 to 0.72 mM at the reaction time of 130 h was observed, when the surfactantbis (2-ethylhexyl) sodium sulfosuccinate (AOT) was added in the reaction mixture. The presence of a small amount of exogenously added water dramatically activated the enzyme in AOT/cyclohexane-reversed micelles. Desorption of the surfactant molecule from the enzyme mass and solubilization of the enzyme into reversed micelles were used to elucidate an existing maximum of the initial rate of (S)-naproxen synthesis with the water content. Moreover, the effects of alcohol and surfactant concentration on the enzyme activity are reported.     

Micelle Formation and Aggregate Morphology Transition from Vesicle to Rod Micelle for Allyl Alkyldimethylammonium Bromide Cationic Surfactant

A series of cationic surfactants of allyl alkyldimethylammonium bromide (AA_nDB), where n=12, 16, 18, were synthesized, and the adsorption behavior of AA_nDB at the air–water interface and the aggregation morphology in bulk solution were reported. The critical micelle concentration (CMC) was determined by the drop volume technique and steady state fluorescence. The surface excess concentration of AA_nDB surfactants was calculated from the surface tension versus log concentration curves by applying the Gibbs' adsorption isotherm. The values of surface area per molecule calculated by using Gibbs' equation were 2.9–1.4 nm², indicating the relatively large size of the AA_nDB surfactants. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements reveal that, at low surfactant concentration of allyl dodecyl dimethylammonium bromide (AA₁₂DB) above CMC, vesicles can be spontaneously formed. However, with increasing surfactant concentration, vesicles tend to be transformed into rod‐like micelles.     

Aggregation behavior of thermo-responsive poly(2-oxazoline)s at the cloud point investigated by FCS and SANS

We have studied different thermo-responsive poly(2-oxazoline)s with iso-propyl (iPrOx) and n-propyl (nPrOx) pendant groups in aqueous solutions, where they exhibit lower critical solution temperature behavior. This paper focuses on the effect of the degree of polymerization, n, the concentration, c, in the dilute regime, and the presence of hydrophobic moieties. The cloud points were investigated as a function of the degree of polymerization, n, and of the polymer concentration, c. The aggregation behavior near the cloud point was studied by temperature-resolved small-angle neutron scattering and fluorescence correlation spectroscopy, i.e., a combination of ensemble and single molecule methods. We found that at the cloud points, large aggregates are formed and that the cloud points depend strongly on both, n and c. Diblock copolymers from iPrOx and nPrOx form large aggregates already at the cloud point of PnPrOx, and, unexpectedly, no micelles are observed between the cloud points of the two blocks. Gradient copolymers from iPrOx and n-nonyl-2-oxazoline (NOx) display a complex aggregation behavior resulting from the interplay between intra- and intermolecular association mediated by the hydrophobic NOx blocks. Above the cloud point, an intermediate temperature regime with a width of a few Kelvin was found with small but stable polymer aggregates. Only at higher temperatures, larger aggregates are found in significant number.     

Effect of alcohols on the micellar properties in aqueous solution of alkyltrimethylammonium bromides

The effect ofn-butanol,n-propanol, andn-hexanol on the critical micelle concentration (CMC) and degree of ionisation of the micelles of dodecyl-, tetradecyl- and hexadecyltrimethylammonium bromides in aqueous solution has been determined by conductimetric techniques. Increase of the molality of added alcohol over the concentration ranges examined (up to 0.3 mol kg^–1 butanol, 0.07 mol kg^–1 pentanol and 0.025 mol kg^–1 hexanol) caused a progressive decrease of CMC and increase of the degree of ionisation for each surfactant-alcohol system. At a constant molality of added alcohol the degree of ionisation increased with a) an increase of the chain length of the surfactant for each alcohol and b) an increase of the chain length of the alcohol for each surfactant. The distribution of each alcohol between the aqueous and micellar phases and the free energy of solubilization were determined from the change of CMC with molality of added alcohol.     

有机相酶催化拆分制备(S)-2-氯-1-(2-噻吩)-乙醇

首次在有机相中对酶催化条件下的2-氯-1-(2-噻吩)-乙醇的反应进行了研究. 通过对不同来源酶的筛选, 找到了Novozym 435和Alcaligenes sp两种选择性较好的酶, 它们均对该反应具有较高的选择性和较快的反应速度, 在此基础上进一步通过对溶剂、温度、摇床转速以及酶用量的筛选, 确定了能够有效拆分2-氯-1-(2-噻吩)-乙醇的较佳反应条件. 当温度35 ℃, 酶量10 mg/mL, 反应72.5 h, 产物的ee值为98.5%时收率为48.6%.     

The Effect of Sodium Dodecylbenzenesulfonate (SDBS) Micelles on a BelousovZhabotinsky Oscillating System Catalyzed with a Tetraazamacrocyclic Copper(II) Complex

This article deals with the influence of micelles of the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) on the Belousov? Zhabotinsky (B? Z) oscillating reaction catalyzed by a tetraazamacrocyclic copper(II) complex [CuL](ClO₄)₂, an enzyme‐like catalyst (L=5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene). Unlike the classical B? Z oscillator in which malonic acid is usually used as a substrate, malic acid (an intermediate in the Krebs cycle) is involved in this oscillating system. Experiments reveal that formation of the SDBS micelles markedly affects the behavior of the oscillating reaction. It is found that there is a linear relationship between the change in the oscillation amplitude (ΔA) and the concentration of SDBS, whereas the change in the oscillation period (ΔT) is linearly proportional to the SDBS concentration. The most likely mechanism that involves the formation of the SDBS micelles and the effects of the micelles on the oscillating chemical system can be rationalized by assuming that the SDBS micelles are so negatively charged that they attract more [CuL]³⁺ than [CuL]²⁺. This hypothesis was confirmed by UV/VIS spectrophotometric measurements of a constant concentration of [CuL](ClO₄)₂ in different concentrations of SDBS; as the SDBS concentration increased, the absorbance of [CuL](ClO₄)₂ increased, while the maximum absorption wavelength for [CuL](ClO₄)₂ remained at 502 nm.     

Self-aggregation of dendritic poly(benzyl ether)–poly(acrylic acid), an amphiphilic block copolymer, studied by 1H NMR

The dynamic properties of the micelles of a novel synthesized amphiphilic block copolymer, dendritic poly(benzyl ether)–poly(acrylic acid) (Dendr.PBE-PAA), formed in aqueous solutions were studied by the ¹H self-diffusion coefficient, relaxation measurements and 2D nuclear Overhauser enhancement spectroscopy. The experimental results show that Dendr.PBE-PAA molecules self-aggregate in aqueous solution. The dynamic properties of the Dendr.PBE-PAA micelles vary with their total concentration in the solution. The motion of the molecules in the micelles of a concentrated solution is more restricted than that in a less concentrated one. The main chains of PAA are densely packed in the surface layer of the hydrophobic core with the carboxyl side chain pointing to the aqueous medium and the hydrophobic phenoxy rings stay in the interior. The self-aggregate becomes larger as the degree of polymerization of PAA increases. However the phenoxy rings situated in the interior of the hydrophobic core become more loosely packed. n-Hexadecane is solubilized in the micelles. The optimal position of n-hexadecane is between the phenoxy rings next to the PAA chains. Received: 25 January 2001 Accepted: 18 July 2001     

Synthesis and Characterization of Thermo-responsive Poly(N-vinyl-2-pyrrolidinone)-block-poly(N-isopropylacrylamide) Micelles

A novel thermo-responsive diblock copolymer of poly(N-vinyl-2-pyrrolidinone)-block-poly(N-isopropylacrylamide) (PNVP-b-PNIPAM) was synthesized. FT-IR, ¹H-NMR and SEC results confirmed the successful synthesis of PNVP-b-PNIPAM diblock copolymer via anionic polymerization. The polymeric micelles formed from PNVP-b-PNIPAM copolymer in aqueous solution were developed and characterized as a potential thermo-responsive and biocompatible drug delivery system. Micellization of the diblock copolymer in aqueous solution was characterized by dynamic laser scattering (DLS), turbidity measurement, tension measurement and transmission electron microscopy (TEM). The thermo-responsive polymeric micelles with the size ranges of 200 to 260 nm and thickness of 30 nm are localized, selected and targeted for drug release, having a great potential in response to external-stimulus such as temperatures from 35 to 39°C. The critical micellization concentration (cmc) of PNVP-b-PNIPAM in aqueous solution is 0.0026 wt% determined by turbidity measurement. The size of micelles determined by DLS increased from 163 to 329 nm with increasing concentration of PNVP-b-PNIPAM from 0.25 to 0.5 wt% in aqueous solution at 40°C, which is determined by DLS.     

Extraction kinetics and ultrafiltration removal of Nickel (II) by long chain alkoxypicolinic acids in cationic and mixed micelles

Micellar particles can solubilize lipophilic extractants similarly to the organic phase in classical biphasic extraction. This analogy is used here to investigate the kinetics of complex formation between Ni²⁺ ions and long chain 5-alkoxypicolinic acids (C_n-PIC, withn=12, 15, 18) solubilized in different types of micelles, namely cetyl trimethylammonium bromide (CTAB), hexaethyleneglycol-dodecylether (C₁₂EO₆) and CTAB/C₁₂EO₆ mixed micelles. In the case of CTAB micelles, the interaction between the carboxylic function of the extractant and the polar head of surfactant molecules was expected to decrease the rate of complex formation so as to make possible kinetic separation of mixtures of metal ions. The observed rate constants for complex formation at pH 4.5 or 7.0 are indeed much smaller in CTAB micelles than in C₁₂EO₆ or mixed micelles, but they still remain too high for the previous purpose, although the influence of the surfactant concentration demonstrates, as expected, a much stronger partitioning in the case of CTAB in comparison to C₁₂EO₆. On the other hand, it is shown that, once complex formation has occurred the removal of Ni²⁺ ions can be achieved using ultrafiltration. The yield of extraction increases withn, with the mole fraction of C₁₂EO₆, and with the ligand to metal ratio.Institut Nancéien de Chimie Moléculaire (I.N.C.M.)     

Formation of polymeric micelles with amino surfaces from amphiphilic AB‐type diblock copolymers composed of poly(glycolic acid lysine) segments and polylactide segments

Amphiphilic AB‐type diblock copolymers composed of hydrophobic poly(L ‐lactide) (PLA) segments and hydrophilic poly(glycolic acid lysine) [poly(Glc‐Lys)] segments with amino side‐chain groups self‐associated to form PLA‐based polymeric micelles with amino surfaces in an aqueous solution. The average diameter of the loose core–shell polymeric micelles for poly(Glc‐Lys) [number‐average molecular weight (M_n) = 1240]‐b‐PLA (M_n = 7000) obtained by a dimethyl sulfoxide/water dialysis method was estimated to be about 50 nm in water by dynamic light scattering measurements. The size and shape of the obtained polymeric micelles were further observed with transmission electron microscopy and atomic force microscopy. To investigate the possibility of applying the obtained PLA‐based polymeric micelles as bioabsorbable vehicles for hydrophobic drugs, we tested the entrapment of drugs in poly(Glc‐Lys) (M_n = 1240)‐b‐PLA (M_n = 7000) micelles and their release with doxorubicin as a hydrophobic drug. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1426–1432, 2002     

Catalytic activity of Pd(II) and Pd(II)/DAB-R systems for the Heck arylation of olefins

Palladium-catalyzed reactions of aryl bromides with various olefins involving Pd(II)/diazabutadiene (DAB-R) systems have been investigated. The scope of a coupling process using Pd(II) sources and an α-diimine as ligand in the presence of Cs₂CO₃ as base was tested using various substrates. The Pd(OAc)₂/DAB-Cy (1, DAB-Cy=1,4-dicyclohexyl-diazabutadiene) system presents the highest activity with respect to electron-neutral and electron-deficient aryl bromides in coupling with electron rich olefins. The synthesis and X-ray characterization of a Pd(II)-diazabutadiene ligand is reported. Extensive optimization experiments showed that another Pd(II) source, Pd(acac)₂ (acac=acetylacetonate), proved to activate aryl bromides at high temperatures, low catalyst loadings when the appropriate concentration of ⁿBu₄NBr additive was employed. The effect of the DAB-Cy ligand is important at very low catalyst loadings and high temperatures. Pd(acac)₂ and Pd(acac)₂/DAB-Cy precatalysts were very effective for the arylation of various olefins with aryl bromides with respect to reaction rate, catalyst loadings, and functional group tolerance.     

Synthesis and crystal structure of a mixed-ligand bismuth(III) complex, [Bi2(phen)2Br5(NO3)] n (phen = 1,10-phenanthroline)

Complex [Bi₂(phen)₂Br₅(NO₃)] _n has been synthesized by reaction of Bi(NO₃)₃ with potassium bromide and 1,10-phenanthroline. The complex has been isolated and characterized by IR-, ¹H NMR-, ¹³C NMR spectrum and elemental analysis. The structure of the [Bi₂(phen)₂Br₅(NO₃)] _n was confirmed by X-ray crystallography which shows the complex to be a one-dimensional polymer as a result of bridging bromides. The two Bi atoms have different environments, six and seven coordinate.     

Synthesis and characterization of well‐defined,amphiphilic poly(N‐isopropylacrylamide)‐ b‐[2‐hydroxyethyl methacrylate‐poly(ϵ‐caprolactone)]n graft copolymers by RAFT polymerization and macromonomer method

The well‐defined, thermosensitive and biodegradable graft copolymers, poly(N‐isopropylacrylamide)‐b‐[2‐hydroxyethyl methacrylate‐poly(ε‐caprolactone)]_n (PNIPAAm‐b‐(HEMA‐PCL)_n) (n = 3 or 9), were synthesized by combining reversible addition‐fragmentation chain transfer polymerization and macromonomer method. The copolymers were able to self‐assemble into micelles in water with low critical micellar concentration and demonstrated temperature sensitivity with a lower critical solution temperature at around 36 °C. Transmission electron microscopy shows that the micelles exhibit a nanosized spherical morphology within a size range of 30–100 nm. The PNIPAAm‐b‐(HEMA‐PCL)₃ copolymer exhibited biodegradation and low cytotoxicity. The paclitaxel‐loaded PNIPAAm‐b‐(HEMA‐PCL)₃ micelles displayed thermosensitive controlled release behavior, which indicates potential as drug carriers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5354–5364, 2007     

A three‐dimensional AlIII/NaI metal–organic framework resulting from dimethylformamide hydrolysis

The three‐dimensional metal–organic framework poly[bis(dimethylammonium) [hexa‐μ₂‐formato‐κ¹²O:O′‐aluminium(III)sodium(I)]], {(C₆H₈N)₂[AlNa(HCOO)₆]}_n, was obtained serendipitously and has been characterized by X‐ray diffraction. The product has arisen as a result of a hydrolysis reaction of dimethylformamide (DMF) and contains dimethylammonium (DMA) cations included in structural voids formed by a three‐dimensional [AlNa(HCOO)₆]⁻ network. This study provides evidence that, in the presence of traces of aluminium, DMF stored in a glass bottle can be hydrolysed to formate and dimethylamine with simultaneous extraction of Na⁺ cations from the glass. It also demonstrates that care must be taken regarding the metal and water content when DMF is not freshly distilled, since the hydrolysis of amide can occur.     

The effect of structure on the thermoresponsive nature of well‐defined poly(oligo(ethylene oxide) methacrylates) synthesized by ATRP

Statistical copolymers of di(ethylene glycol) methyl ether methacrylate (MEO₂MA) and tri(ethylene glycol) methyl ether methacrylate (MEO₃MA) were synthesized by atom transfer radical polymerization (ATRP) providing copolymers with controlled composition and molecular weights ranging from M_n = 8,300–56,500 with polydispersity indexes (M_w/M_n) between 1.19 and 1.28. The lower critical solution temperature (LCST) of the copolymers increased with the mole fraction of MEO₃MA in the copolymer over the range from 26 to 52 °C. The average hydrodynamic diameter, measured by dynamic light scattering, varied with temperature above the LCST. These two monomers were also block copolymerized by ATRP to form polymers with molecular weight of M_n = 30,000 and M_w/M_n from 1.12 to 1.21. The LCST of the block copolymers shifted toward the LCST of the major segment, as compared to the value measured for the statistical copolymers at the same composition. As temperature increased, micelles, consisting of aggregated PMEO₂MA cores and PMEO₃MA shell, were formed. The micelles aggregated upon further heating to precipitate as larger particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 194–202, 2008     

Synthesis and pH-sensitive micellization of doubly hydrophilic poly(acrylic acid)-b-poly(ethylene oxide)-b-poly(acrylic acid) triblock copolymer in aqueous solutions

A doubly hydrophilic triblock copolymer poly(acrylic acid)-b-poly(ethylene glycol)-b-poly(acrylic acid) (PAA-b-PEO-b-PAA) with M _w/M _n = 1.15 was synthesized by atom transfer radical polymerization of t-butyl acrylate (tBA), followed by acidolysis of the PtBA blocks. The pH-sensitive micellization of PAA-b-PEO-b-PAA in acidic solution was investigated by potentiometric titration, fluorescence spectrum, dynamic light scattering and zeta potential. The pK _a was 6.6 and 6.0 in deionized water and in 0.1 mol/L NaCl solution, respectively. The copolymer formed micelles composed of a weakly hydrophobic core of complexed PAA and PEO and a hydrophilic PEO shell in 1 mg/mL solution at pH < 5.5 due to hydrogen bonding. The critical micelle concentration was 0.168 mg/mL at pH 2.0. At pH < 4.5, steady and narrow distributed micelles were formed. Increasing pH to 5.0, unsteady and broad distributed micelles were observed. At pH > 5.5, the micelle was destroyed owing to the ionization of the PAA blocks.     

RAFT synthesis of polystyrene‐block‐poly(polyethylene glycol monomethyl ether acrylate) for zinc phthalocyanine‐loaded polymeric micelles as photodynamic therapy photosensitizers

A series of polystyrene‐block‐poly(polyethylene glycol monomethyl ether acrylate) (PSt_m‐b‐PPEGA_n) polymers were systematically synthesized as carriers for zinc phthalocyanine (ZnPc) for photodynamic therapy via reversible addition and fragmentation chain transfer polymerization. The degree of polymerization of the styrene (m) and PEGA units (n) of the resulting block copolymers were characterized to be n = 174, 40, and 18 for m = 52; and n = 200, 84, and 31 for m = 30. All the block copolymers formed micelles in water. The critical micelle concentration (CMC) of the PSt_m‐b‐PPEGA_n was determined by fluorometry using pyrene as a hydrophobic probe. The CMC value increased from 4.5 to 20 mg·L⁻¹ with an increase in the mole fraction of PEGA units. The median diameters of the micelles increased from 19 to 31 nm for PSt₅₂‐b‐PPEGA_n and from 15 to 23 nm for PSt₃₀‐b‐PPEGA_n with increasing n value. ZnPc‐loaded micelles were prepared by dialysis of the block copolymer in the presence of ZnPc followed by removal of large aggregates by filtration. The encapsulation efficiency was dramatically changed in the range of 0–68%. The light‐dose‐dependent cytotoxicity of the ZnPc‐loaded PSt₃₀‐b‐PPEGA₂₀₀ was clearly established in HeLa cell lines; while no cytotoxicity was confirmed under the dark. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 560–570     

Conductive and anticorrosive poly(N-alkyl-2-(4-hydroxybut-2-ynyl) pyridinium bromides): Synthesis and characterization

Present work reports a new type of poly(N-alkyl-2-[4-hydroxybut-2-ynyl] pyridinium bromides) (designated as Po-n, n = 8, 12, 16 of carbon atoms in the alkyl chain). Po-n were synthesized and characterized by FTIR, GPC, and NMR analysis. The possible polymerization mechanism was proposed and supported by theoretic calculation. A preliminary probe was performed on the conductivity and anticorrosive ability of the conjugated polymer. The results showed that these polymers demonstrated poor conductivity, however the conductivity was enhanced by graphene doping. Po-n are good inhibitors for X70 steel corrosion in HCl solution. So, the conjugated polymers may play important roles in the fields of optoelectronic devices and steel corrosion inhibition.