Polymerised ionic liquid crystals bearing imidazolium and bipyridinium groups

Novel kinds of polymerised ionic liquid crystals (PILCs) bearing imidazolium and bipyridinium groups were synthesised and characterised in this work. Some bromo-polyesters were synthesised in an esterification chain reaction using 2,3-dibromosuccinyl dichloride, isophthaloyl chloride and 4,4′-biphenol. The polyester imidazolium bromides (PIBs) and polyester dipyridinium bromides (PDBs) were obtained by a quaternisation reaction between the bromo-polyesters, N-methylimidazole and 4-4′-bipyridine, respectively. The polyester imidazolium tetrafluoroborates (PITs) and polyester dipyridinium tetrafluoroborates (PDTs) were synthesised using the corresponding PIBs and PDBs in an anion-exchange reaction. The chemical structures, liquid crystalline properties and molecular weights of these polymers were characterised by multiple experimental techniques. All the PILCs including PIBs, PDBs, PITs and PDTs display smectic A phase on heating and cooling cycles. The liquid-crystalline properties of bromo-polyesters are influenced by the length of flexible spacer and composition of polyester backbones, while those of PILCs are determined by the ionic groups as additional important influent factors. In comparison with those of the mother bromo-polyesters, the d-spacing of PILCs reduced slightly due to Im⁺–Br^?, Dp⁺–Br^?, Im⁺–BF₄^? and Dp⁺–BF₄^? ion pairs in the polymer systems. Monocationic imidazolium salts display weaker interionic and intermolecular interaction, higher mobility and lower viscosity than dicationic dipyridinium salts.     

Arsenic-containing ribofuranosides and dimethylarsinic acid in green seaweed,Codium fragile

Three water-soluble arsenic compounds were isolated from the green seaweed Codium fragile. These compounds were identified as 1-glycerophosphoryl-2-hydroxy-3-[5′-deoxy-5′-(dimethylarsinoyl)-β-ribofuranosyloxy]propane (1a), 1′ -(1,2-dihydroxypropyl)-5′ -deoxy-5′ -(dimethylarsinoyl)-β-ribofuranoside (1b), and dimethylarsinic acid ((CH₃)₂AsOOH). The structures of these compounds were ascertained by ¹H NMR spectroscopy. Compounds 1a and 1b accounted for 60 % and dimethylarsinic acid for 5% of the water-soluble arsenic.     

Synthesis of Cyclodextrin and Sugar-Based Oligomers for the Efavirenz Drug Delivery

Summary: In the present work water-soluble lactose based oligomers of β-cyclodextrin were synthesized by a simple and efficient condensation polymerization process. Proposed water-soluble β-cyclodextrin oligomers were prepared by controlled reaction between β-cyclodextrin and a triazine linker and purification by an ultrafiltration process. Similarly, lactose based β-cyclodextrin oligomers were synthesized for enhanced water solubility. The physical and chemical properties of the synthesized polymers were characterized by FT-IR and ¹H NMR spectroscopy, XRD analysis, thermogravimetric analysis (TGA) and aqueous solubility determination.. Molecular weights of these β-cyclodextrin based oligomers were measured by ESI technique. These β-cyclodextrin based water-soluble oligomers polymers were used as supramolecular carriers for efavirenz (an anti HIV drug), improving the inclusion property and aqueous solubility properties of this drug. These synthesized oligomers were found to improve stability and aqueous solubility of efavirenz on their (1:1) inclusion complex through phase solubility and dissolution studies. Reduced cytotoxicity than the parent β-CD was observed in hemolysis test.     

Chemoselective polyesterification by direct polycondensation

A convenient method for the synthesis of polyester‐containing amino substitutes on the aromatic rings of the backbone has been developed. This polyester was prepared by chemoselective polyesterification of isophthalic acid with bisphenol having an amino group in the presence of the condensing agent diphenyl(2,3‐dihydro‐2‐thioxo‐3‐benzoxazolyl)phosphonate ( 1 ) and 1,5‐diazabicyclo[4,3,0]‐5‐nonene as a base. The model reactions were carried out in detail to elucidate appropriate conditions of chemoselective polyesterification. Direct polycondensation of isopthalic acid with 4,4′‐[1‐(4‐aminophenyl)ethylidene]bisphenol proceeded smoothly under mild conditions and produced the desired polyester with a number average molecular weight of 11,000 and M_w/M_n of 2.22. The polymer obtained was characterized by IR, ¹H, and ¹³C NMR spectroscopies. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 78–85, 2001     

The Inclusion Properties of a New Watersoluble Sulfonated Calix[4]resorcinarene towards Alkylammonium and N-Methylpyridinium Cations

The inclusion behaviour of a new water-soluble sulfonated calix[4]resorcinarene towards alkylammonium and N-methylpyridinium cations has been investigated on the basis of ¹H NMR spectroscopy and pH-potentiometry data. The inclusion of the N-methylpyridinium cation has been found to be dependent on pH with the preferable inclusion of the methyl substituent in alkaline and the aromatic ring in neutral aqueous media.     

Stereoselective Inclusion and Structure of Equatorial-trans-1,2-dichlorocyclohexane

Abstract

Optically active (R,R)-(-)-trans-1,2-dichlorocyclohexane (DCC) was isolated as an inclusion crystal with the optically active host, (R,R)-(-)-trans-2,3-(hydroxydiphenylmethyl)-1,4-dioxaspiro[4.4]-nonane, and the structure of the 2:1 inclusion crystal has been determined by X-ray analysis. Crystal data: C₇₂H₇₄O₈Cl₂, orthorhombic, P2₁2₁2 (No. 18), a = 17.465(6) Å, b = 20.095(6) Å, c = 8.664(5) Å, V = 3040(2) ų, Z = 2, D_c = 1.24g cm^?3, D_m = 1.23g cm^?3, T = 293 K and final R ₁ = 0.050 for 2766 observed data (I > 2σ(I)). The conformation of DCC in the inclusion crystal has been found to be equatorial and the absolute configuration was definitely determined to be (R,R) on the basis of the known configuration of the host.     

Mechanism for the inhibition of the acid degradation of ampicillin by 2-hydroxypropyl- β -cyclodextrin

The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution. In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry: the first-type had a high association constant K ₁ of 4.0-8.0·10³ M^-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K ₂ of 1.0·10³ M^-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in a two-step reaction and was characterized by a smaller K _1:2of 4.0·10² M^-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37°C. In weak acid and neutral solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl group was included (Mode II). AMPC was very stable in these solutions (t _1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Living cationic polymerization of vinyl ethers with a functional group. VII. Polymerization of vinyl ethers with a silyloxyl group and synthesis of polyalcohols and related functional polymers

Living cationic polymerizations of two silicon-containing vinyl ethers, 2-(t-butyldimethyl-silyloxyl)ethyl vinyl ether (tBuSiVE) and 2-(trimethylsilyloxyl)ethyl vinyl ether (MeSiVE), have been achieved with use of the hydrogen iodide/iodine (HI/I₂) initiating system in toluene at ?15 or ?40°C, despite the existence of the acid-sensitive silyloxyl pendants. The living nature of the polymerizations was demonstrated by linear increases in the number-average molecular weights (M?_n) of the polymers in direct proportion to monomer conversion and by their further rise upon addition of a second monomer feed to a completely polymerized reaction mixture. The polymers obtained in these experiments all exhibited very narrow molecular weight distributions (MWD) with M?_w/M?_n around or below 1.1. Desilylation of the polymers under mild conditions (with H⁺ for MeSiVE and F^? for tBuSiVE) gave poly(2-hydroxyethyl vinyl ether), a water-soluble polyalcohol with a narrow MWD. The living processes also permitted clean syntheses of amphiphilic AB block copolymers and water-soluble methacrylate-type macromonomers, all of which bear narrowly distributed segments of the polyalcohol derived from the silicon-containing vinyl ethers.     

Alternating copolymerization of propylene oxide with carbon monoxide catalyzed by Co complex and Co/Ru complexes

Co₂(CO)₈ catalyzes the ring‐opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The ¹H and ¹³C{¹H} NMR spectra of the polyester, obtained by the Co₂(CO)₈–3‐hydroxypyridine catalyst, show the following structure ? [CH₂? CH(CH₃)? O? CO]_n? . The Co₂(CO)₈–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring‐opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N′,N′‐tetramethylethylenediamine, enhance the Co complex‐catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)_n (R = Me or CH₂Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co₂(CO)₈? Ru₃(CO)₁₂ mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the Ru? Co mixed‐metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002     

Modification of the luminescence properties of an Europium(III) Tris(β-diketonate) Complex by Inclusion in γ-cyclodextrin and 2,3,6-trimethyl-γ-cyclodextrin

A 1:1 inclusion compound between octakis(2,3,6-tri-O-methyl)-γ-cyclodextrin (TRIMEG) and the chelate complex Eu(NTA)₃·2H₂O (NTA=1-(2-naphthoyl)-3,3,3-trifluoroacetonate) was prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and photoluminescence spectroscopy. The results were compared with those obtained for the corresponding native γ-CD adduct. Excitation and emission spectra were measured, and the lifetimes were determined for the Eu³⁺ first excited state (⁵D₀). The results indicate the presence of only one low-symmetry environment for the Eu³⁺ cations in the inclusion compounds. Encapsulation of the Europium complex in the two CDs increases the quantum efficiency of the ligand-to-metal energy transfer pathway, but the efficiency of the Eu³⁺ sensitization was significantly higher with TRIMEG as the host molecule. This may be related with the observation that the two hosts appear to have different influences on the Eu³⁺ coordination environments for the guest molecule.     

Sulfonation of 3,3′-Diformyl-BINOL for Enantioselective Fluorescent Recognition of Amino Acids in Water

Reaction of (R)-3,3′-diformyl-1,1′-bi-2-naphthol with concentrated sulfuric acid gives the corresponding 6,6′-disulfonated compound (R)- 2 selectively. This provides a simple and efficient method to convert a water-insoluble compound to a water-soluble fluorescent probe. It is found that (R)- 2 in combination with Zn²⁺ shows a highly enantioselective fluorescent response toward various amino acids in the aqueous HEPES buffer solution at pH 7.4. For example, an enantioselective fluorescence enhancement ratio [ef=ΔI_D/ΔI_L] up to 35.8 is observed for the recognition of asparagine. NMR and mass spectroscopic investigations are conducted to explore the reaction of (R)- 2 with asparagine.     

Selenate—An internal chemical shift standard for aqueous 77Se NMR spectroscopy

The ⁷⁷Se NMR spectra of selenate were studied under various circumstances, such as concentration, pH, temperature, ionic strength, and D₂O:H₂O ratio, in order to examine its potential as a water-soluble internal chemical shift standard. The performance of selenate as a chemical shift reference and that of other attempted ones from the literature (dimethyl selenide, tetramethylsilane/TMS, and 3-(trimethylsilyl)propane-1-sulfonate/DSS) was also explored. The uncertainty in the resulting chemical shift relative to the effective spectral width is comparable to that of DSS. Compared to the currently prevalent water-soluble external chemical shift reference, selenic acid solution, the properties of internal selenate are much more favorable in terms of ease of use. We have also demonstrated that selenate can be used in reducing media, which is inevitable for the analysis of selenol compounds. Thus, it can be stated that sodium selenate is a robust internal chemical shift reference in aqueous media for ⁷⁷Se NMR measurements; the chemical shift of this reference in a solution containing 5 V/V% D₂O at 25°C and 0.15 mol·dm⁻³ ionic strength is 1048.65 ppm relative to 60 V/V% dimethyl selenide in CDCl₃ and 1046.40 ppm relative to the ¹H signal of 0.03 V/V% TMS in CDCl₃. In summary, a water-soluble, selenium-containing internal chemical shift reference compound was introduced for ⁷⁷Se NMR measurements for the first time in the literature, and with the aforementioned results all previous ⁷⁷Se measurements can be converted to a unified scale defined by the International Union of Pure and Applied Chemistry.     

Esterification reactions on syndiotactic poly(2-methallyl alcohol). V. Homopolymers of 2-methallyl-(L)-dipeptidates and dipeptides cleaved from them

Syndiotactic poly(2-methallyl alcohol) (sPMA) is esterified with N^α-protected (L)-α-amino acids by the DCC/HOBT method. The resulting polymer is deprotected by HBr/glacial acetic acid. A second N^α-protected (L)-α-amino acid is condensed to the free α-NH₂ of the amino acid already bound to the sPMA by a water-soluble carbodiimide in mixed aqueous/organic solution. The formed N^α-protected dipeptide polymers were hydrazinolized to yield the N^α-protected dipeptide hydrazides. Alternatively, the dipeptidate polymers were N^α-deprotected and then hydrolyzed by aqueous KOH at pH = 11.0 to yield the deprotected dipeptides. All polymers and the dipeptides were characterized by ¹H- and ¹³C-NMR and the water-soluble N^α-deprotected polymers in addition by potentiometry. The synthetic procedures open a path to defined tactic polymers with chiral oligopeptide side chains and, after their cleavage, also to oligopeptides. During synthesis, the oligopeptide is bound to a dissolved polymer chain of relatively extended macroconformation which facilitates both the accessibility and reactivity of the reaction centers as well as the precipitation and filtration after each synthesis step. © 1995 John Wiley & Sons, Inc.     

Synthesis of end-capped polyester from SmI2-catalyzed Tishchenko-type polyaddition of dialdehydes

SmI₂-catalyzed polyaddition of 1,12-dodecanedial followed by treatment with benzaldehyde gives a polyester (1) containing three structural units, [OCH₂-(CH₂)₁₀-CH₂O], [OCH₂-(CH₂)₁₀-CO], and [CO-(CH₂)₁₀-CO], in the main chain and an OCH₂Ph end-capping group. GPC analysis of 1 shows molecular weights of M_n = 5.5 × 10³ and M_w = 14 × 10³. The ¹H-NMR spectrum reveals the polymer structure with the COOCH₂Ph end group as well as the M_n value (2.6 × 10³) calculated based on an amount of the end-capping group and lower than that estimated from GPC. Mixtures of terephthalaldehyde and 1,12-dodecanedial in several molar ratios undergo similar polyaddition catalyzed by SmI₂ to give the corresponding copolyesters after treatment with benzaldehyde. Increase in the ratio of 1,12-dodecanedial causes increase in yield and molecular weight of the copolymer. Terephthalaldehyde shows a tendency to give alcohol-side —O—R—O— unit in the polyester, whereas 1,12-dodecanedial is mostly incorporated as the acid-side —CO—R′—CO— unit. Terminal aldehyde group derived from dodecanedial is capped effectively by benzaldehyde to give the COOCH₂Ph end group. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2821–2825, 1997     

Preparation of Polyester Polyol from Epoxidized Palm Olein

In this work, polyester polyols with high weight average molecular weight (M_w) (M_w?10000–15000) were prepared from epoxidized palm olein (EPO_o) and a series of dicarboxylic acids (C₆–C₁₂) at elevated temperature under non‐catalyzed condition. The optimal reaction conditions were determined as 180°C for 4 h. Longer carbon chain length of dicarboxylic acids was more reactive when reacted with EPO_o. The physical appearance of the product was observed as liquid at room temperature. This palm oil‐based polyester polyol is proposed as starting material for flexible polyurethane. For reaction monitoring purposes, FTIR was used while ¹H NMR analysis was carried out to characterize the important functional groups of the products. The effects of reaction time and temperature on the M_w of the reaction mixture were also studied by GPC.     

Ru and Sm catalyzed polyaddition of dialdehydes to give polyesters. Application of Tishchenko type reactions to polymer synthesis

RuH₂(PPh₃)₄ catalyzed Tishchenko type polyaddition of terephthal-aldehyde gives aromatic polyester ( 1 ), which contains three structural units, [OCH₂ C₆H₄ CH₂O] ( 1a ), [OCH₂ C₆H₄ CO] ( 1b ), and [CO C₆H₄ CO] ( 1c ). ¹H-NMR spectrum shows the presence of the three units in a 1 : 2 : 1 ratio. Isophthalaldehyde also undergoes similar polyaddition to give another aromatic polyester ( 2 ), while 1,12-dodecanedial gives an aliphatic polyester ( 3 ) containing the following structural units: [OCH₂ (CH₂)₁₀ CH₂O] ( 3a ), [OCH₂ (CH₂)₁₀ CO] ( 3b ), and [CO (CH₂)₁₀ CO] ( 3c ). The above polymers have M_n of 2.7 × 10³−5.4 × 10³ and M_w of 4.3 × 10³ − 9.7 × 10³, respectively. Mixtures of terephthalaldehyde and 1,12-dodecanedial produce copolymers, which contain the units 1a–1c and 3a–3c in a random sequence. In the copolymerization, terephthalaldehyde shows a strong tendency to give 1c units, whereas 1,12-dodecanedial predominantly affords 3a units. SmI₂ also catalyzes polyaddition of terephthalaldehyde to give the corresponding polyester with M_n of 1.7 × 10³ and M_w of 3.7 × 10³, respectively. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1265–1273, 1997     

Synthesis and nonlinear optical properties of polyester containing 4‐di‐(2′‐hydroxyethoxy)‐4‐diphenyl‐hydrazonomethyl chromophore

The nonlinear optical property of new polyester has been studied via second harmonic generation (SHG). The values of electro‐optic coefficients, d₃₃ and d₃₁, of the poled polymer film were 3.15 × 10 ^?7 and 1.5 × 10^?7 esu, respectively. Thermal behavior of this polyester was studied through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). 4‐di‐(2′‐hydroxyethoxy)‐4‐diphenyl‐hydrazonomethyl was synthesized from the reaction of 3,4‐dihydroxy‐4‐diphenyl‐hydrazonomethyl with 2–chloro–1‐ethanol in a 1:2 mole ratio and subsequently reacted with terephthaloyl chloride (TPC) in the presence of pyridine, as catalyst, to produce the new nonlinear polyester. The chemical structures of the resulting monomers and polymer were characterized by CHN analysis, ¹H‐NMR, FT‐IR, and UV–Vis spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd.     

Photocontrolled transparent–opaque transition of a thermosensitive homopolymer solution based on an azobenzene–cyclodextrin system

A solution displaying photocontrolled transparent–opaque transition was prepared through combination of a thermosensitive polymer, poly(N-(3-ethoxypropyl)acrylamide) (PEPAAm), with α-cyclodextrin (α-CD) and a water-soluble azobenzene compound, Azo-Py⁺. α-CD increased the cloud point of an aqueous solution of PEPAAm through formation of inclusion complexes between α-CD and the side groups of PEPAAm. After Azo-Py⁺ was added, the cloud point of the solution decreased because most of the α-CD formed complexes with Azo-Py⁺. The concentration of free α-CD was changed by photocontrolled inclusion of Azo-Py⁺ in α-CD or exclusion of Azo-Py⁺ from α-CD, allowing the cloud point of PEPAAm/α-CD/Azo-Py⁺ solution to be changed up and down. Consequently, the transparent–opaque transition of this solution was realised by alternating irradiation with UV and visible light at 38°C.     

New ferrocenyl derivative with controllable aggregation-induced emission (AIE) characteristics

A novel molecular switch, 7-(N,N-diethylamino)-2-oxo-2H-chromen-4-yl ferrocene carboxylate (FCC), was synthesized and fully characterized by ¹H NMR, ¹³C NMR, and HRMS. Taking advantage of the properties of ferrocene as an electron donor active unit and the coumarin as a fluorescent unit, the dyad FCC shows a fast and reversible redox-switchable fluorescence emission. In sharp contrast to most photoluminescent chromophores, FCC has a unique enhanced emission through aggregation. The change of electrochemical signals (CV and DPV) indicated that the ferrocene (F_c) unit of FCC could form inclusion complex with Me-β-cyclodextrin (CD). This inclusion complex could further weaken the aggregation-induced emission (AIE) effect remarkably. This advance paves the way to introduce AIE property into molecular devices applications.     

Synthesis and evaluation of a new water-soluble fluorescent red dye,xanthene bis-C-glycoside

Condensation of 2 eq. of C-β-D-glucosylphloroacetophenone with glyoxylic acid in an aqueous solution of Na₂CO₃, followed by air oxidation in MeOH in the presence of 11 eq. of pyridine to afford a 36% yield of a bright red dye, xanthene bis-C-glycoside. This dye is 10 times more fluorescent (Φ_{f [EtOH]}^{581 nm} = 3.9 × 10⁻²) and 7.5 times more water-soluble (57 mg/mL H₂O) than the natural red pigment, carthamin. Detailed NMR analysis of its methyl analogs was used to confirm the structure of the dye as methyl 4,5-diacetyl-1,3,8-trihydroxy-3-oxo-3H-2,7-di-C-β-D-glucopyranosylxanthene-9-carboxylate from among three possible ring-closure isomers. Xanthene is safe and shows high light-resistance; therefore, xanthene bis-C-glycoside could be used as a food colorant or an in vivo probe.