Polyether Complexes Research Articles

Alkaline aerobic oxidation of native softwood lignin in the presence of Na+-cyclic polyether complexes

Alkaline aerobic oxidation is a promising way to convert lignin to low molecular weight phenols, especially 4-hydroxybenzaldehydes. Our previous studies reported that oxidation of softwood lignin samples with a bulky cation, Bu4N+, facilitates selective production of vanillin (4-hydroxy-3-methoxybenzaldehyde). This study presents vanillin production from native softwood lignin in Japanese cedar (Cryptomeria japonica) in NaOH aq. in the presence of cyclic polyethers, with our expectation that Na+-polyether complexes exhibit effects similar to those of Bu4N+. Oxidation of wood flour (10 mg) in 4.0 M NaOH aq. (2.0 mL) at 120 °C under air gave vanillin with 6.2 wt% lignin-based yield, which was raised to 15.2 wt% by the addition of 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane). On the other hand, such effect was not observed with the addition of tetraethylene glycol dimethyl ether, a non-cyclic analog of 15-crown-5. Mechanistic study with a lignin model compound revealed that stabilization of a vanillin precursor by the complex cation was a reason for the increased vanillin yield exhibited by the crown ether. This is similar to the influence of Bu4N+ reported previously, suggesting effective control of aerobic oxidation by large size cationic species.

Ion–Dipole-Interaction-Driven Complexation of Polyethers with Polyviologen-Based Single-Ion Conductors

The role of solvating polyethers on single-ion conduction and segmental dynamics is investigated for an amorphous main-chain polycation, polyviologen (PV), with two different [−(CH2)6– and −(CH2)10...

Mechanical and Physical Properties of Epoxy and Unsaturated Polyether Complexes Reinforced with Glass Fiber and Nanomaterial Alumina Powder

Mechanical and Physical Properties of Epoxy and Unsaturated Polyether Complexes Reinforced with Glass Fiber and Nanomaterial Alumina Powder

Synthesis and structural characterization of new polyether complexes of germanium(II) and tin(II)

A series of germanium(II) and tin(II) bromide polyether complexes have been synthesized. Specifically, [GeBr([15]crown-5)][GeBr3], [GeBr([18]crown-6)][GeBr3], [GeBr(triglyme)][GeBr3], [GeBr(tetraglyme)][GeBr3], [SnBr([18]crown-6)][SnBr3], [Sn([15]crown-5)2][SnBr3]2, [SnBr(triglyme)][SnBr3], and [SnBr(tetraglyme)][SnBr3] have been fully characterized including by single crystal X-ray diffraction. The synthesis of [GeBr(dibenzo[24]crown-8)][GeBr3] and [GeCl(dibenzo[24]crown-8)][GeCl3] are also reported, along with the crystal structure of the latter’s water adduct, which features a water molecule adjacent to the GeCl+ ion within the cavity of the crown ether.

ChemInform Abstract: Polyether Complexes of Groups 13 and 14

AbstractReview: notable aspects of the chemistry of polyether complexes of group 13 and 14 elements; 191 refs.

Polyether complexes of groups 13 and 14.

Notable aspects of the chemistry of complexes of polyether ligands including crown ethers, cryptands, glycols, glymes, and related polyether ligands with heavier group 13 and 14 elements are reviewed with a focus on results from 2005 to the present. The majority of reported polyether complexes contain lead(ii) and thallium(i) but recent breakthroughs in regard to the preparation of low oxidation state reagents of the lighter congeners have allowed for the generation of complexes containing indium(i), gallium(i), germanium(ii), and even silicon(ii). The important roles of ligand size, donor types, and counter anions in regard to the chemical properties of the polyether complexes is highlighted. A particular focus on the structural aspects of the numerous coordination complexes provides a rationale for some of the spectacular contributions that such compounds have made to Modern Main Group Chemistry.

Surfactant Effects in Cu-Sn Alloy Deposition

Adsorption behavior of different polyethers (PE) on copper and tin was studied in combination with kinetic investigations. No pronounced effect of PE was detected in the Cu|Cu(II) system. In contrast, these substances show a high inhibition activity on the tin electrode. Halides enhance adsorption ability on copper electrode but suppress it on tin; this effect intensifies in the sequence: Cl− < Br− < I−. It is supposed that specifically adsorbed halides can act as species bridging the copper substrate with Cu(I)-polyether complexes, whereas the model of competitive adsorption is more suited for tin substrate. The inhibition degree of surfactants increases with the length of hydrocarbon chain. Underpotential deposition of Sn(II) is observed in the region of Cu(II) limiting current. The characteristic current minimum arises in the region where the free Sn phase becomes thermodynamically stable. Cl− ions broaden the range of current densities where yellow bronze can be obtained, but Br− ions show the opposite effect. Iodides retard the reduction of Cu(II) therefore tin prevails in the coatings. The deposits obtained present a mixture of pure copper, α-CuSn (fcc) phase and hcp phase of α-CuSn.

ChemInform Abstract: Palladium Polyether Diphosphinite Complex Anchored in Polyethylene Glycol as an Efficient Homogeneous Recyclable Catalyst for the Heck Reactions.

Abstract Palladium polyether diphosphinite complex anchored on polyethylene glycol is reported as an efficient catalyst for Heck coupling reactions. The catalyst is soluble in the solvent with reactants and products during reaction and can be separated from reaction media in biphasic form by the addition of anti-solvent like n -hexane and further recycled. The developed methodology offers mild reaction condition, short reaction time with an excellent recyclability of the catalyst. Aryl iodides as well as aryl bromides are well tolerated giving excellent yields.

Electrospray ionization mass spectrometry of the non-covalent complexes of ammonium ions with high molar mass polyethers

The formation of low charge state non-covalent complexes of high molar mass polymers with primary and tertiary amines and quaternary ammonium salts (Quats) was studied by electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). The amines studied were of different degree of substitution and size, and were added to the acidic polymer solution prior to MS analysis. A comparison was made between the non-covalent complexes of high molar mass polyethers with various amines and Quats, based on the ability to form low charge state adduct ions, overall MS response, and presence of fragment ions due to up-front fragmentation. Tertiary amines showed the best performance in forming low charge state adduct ions and produced mass spectra with the lowest degree of up-front fragmentation. In both primary and tertiary amines, more simplified mass spectra are produced, since no cluster ions are formed (as in the case of Quats). The comparison of the overall MS response did not reveal a specific trend. An amine and a Quat with an optimal performance for formation of low charge state adduct ions were applied to the mass spectrometric analysis of a poly(lactic acid)- block-poly(ethylene glycol)- block-poly(lactic acid) triblock copolymer, allowing the detection of low charge state adduct ions and revealing information about the molecular weight distribution. The method demonstrated here shows that addition of primary/tertiary amines and quaternary ammonium salts to the spray solvent facilitates the analysis of high molar mass polyethers by ESI-MS.

Gas–phase complexes of cyclic and linear polyethers with alkali cations

The flexibility of polymer backbones constitutes one key aspect in their molecular recognition properties. This investigation characterizes the structure of the gas-phase complexes formed by the cyclic and linear polyethers with the heavier alkali metal cations. In particular, the cyclic 15-crown-5 ether (15c5), (OCH(2)CH(2))(5), and the polyethylene glycol linear chains PEG4 and PEG9, H(OCH(2)CH(2))(n=4,9)OH, are considered. Infrared multiple photon dissociation spectroscopy is applied to probe the polymer vibrational modes within the spectral range 800-1500 cm(-1), in combination with Density Functional Theory calculations. The experimental spectra of the 15c5-M(+) (M = K, Rb, Cs) complexes correlate with distorted asymmetric backbone structures in which the cation lies above the ether ring, and four oxygens are oriented toward the cation. In contrast, the PEG4-K(+) complex features an inclusion-like fivefold coordination structure in which the cation and four oxygens are quasi-coplanar and one terminal oxygen lies out of plane. For the PEG9-K(+) complex, the ether chain builds stable cages involving a coordination of eight oxygens with the cation, sustained by hydrogen bonds between the terminal hydroxyl groups.

ミクロスケールの海‐島相分離構造を有するＮＢＲ／ポリエーテル電解質ブレンドのイオン伝導性に及ぼす湿度の影響

Novel ion-conductive elastomer blends containing polyether-based solid polymer electrolyte (SPE) were prepared by the radical polymerization of oligo[(ethylene oxide)-co-(propylene oxide)] methacrylate (M(EO/PO)) monomer with LiClO4 in NBR. Obtained samples showed micro- (or nano-) scale Sea-Island phase separation, which was revealed from the TEM observation in case of NBR18/PM(EO/PO)mono-LiClO4 50/50 wt% blend, and the DC conductivity under dry N2 (σdry) was approximately 10–8 S cm–1 at 25 °C. The difference in the conductivity of blend samples between dry and wet conditions was very small, whereas the conductivity of PM(EO/PO)-LiClO4 without NBR under wet condition (σwet) was 10-times higher than σdry. Moreover, the σdry of NBR43 blend sample (NBR43/electrolyte = 30/70 wt%) was higher than that of the neat electrolyte. The complex impedance measurement revealed that AC ionic conductivity of the NBR43 blend sample was 6.7 × 10–6 S cm–1 at 25 °C and the value was approximately 6-times higher than that of the neat electrolyte. This may be caused by accelerated ion-conduction between the electrolyte islands or on the NBR/electrolyte interface where the resistance is very small because of the electrical interactions between Li ions (or Li+−polyether complex domains) and nitrile groups of NBR.

Lanthanide polyether complexation chemistry: the interaction of hydrated lanthanide(iii) nitrate salts with an acyclic 18-crown-6 analog, pentaethylene glycol

The complexation reactions of 1 : 1 molar ratios of M(NO3)3·nH2O (M = Y, La–Pr, Sm–Lu) and pentaethylene glycol (EO5) in 3 : 1 CH3CN : CH3OH were investigated. Crystalline complexes were isolated for all metals investigated and X-ray structural analyses performed. The M(NO3)3–EO5 complexes structurally characterized are remarkably similar to the corresponding 18-crown-6 complexes. Six structurally unique types of anhydrous complexes with the early- to mid-lanthanides (M = La–Nd, Sm–Dy) were found. For the largest metals studied, the twelve coordinate species [M(NO3)3(EO5)] (M = La, Ce) were isolated. A second form of the type [Ce(NO3)2(EO5)]7[Ce(NO3)6][NO3]4 was isolated for M = Ce from the same reaction mixture as the above complex. Praseodymium through dysprosium form ten coordinate species which all have the same basic formula, [M(NO3)2(EO5)][NO3], however, four structurally unique forms have been characterized with the major differences between each arising from the way in which the uncoordinated nitrate anion is hydrogen bonded to the glycol ligand, and the glycol conformation. The smallest lanthanides investigated, M = Ho–Lu, Y, form outer-sphere complexes [M(OH2)3(NO3)3]·EO5. Structural results suggest that the flexibility of the acyclic EO5 ligand allows for the formation of inner sphere complexes across most of the series, whereas the cyclic 18-crown-6 is too constrained to permit such complexation to the mid- to late-lanthanides.

Theoretical studies in local coordination and vibrational spectra of M +CH 3O(CH 2CH 2O) nCH 3 ( n = 2–7) complexes (M = Na, K, Mg and Ca)

Solid polymer electrolytes (SPE) comprised of poly(ethylene oxide) (PEO) oligomers complexed with alkali metal salt of weakly coordinating anions have been of a great interest due to their high ionic conductivity. Ion pair formation influence the number of charge carriers and is an important factor underlying the ion transport phenomenon. In this work, the electronic structure and vibrational spectra of the metal ion-PEO oligomer represented by M-CH 3O(CH 2CH 2O) n CH 3 ( n = 2–7) (M = Na +, K +, Mg 2+ and Ca 2+) are obtained by employing the ab initio and hybrid density functional methods. Structural and spectral consequences of PEO oligomers to the alkali- and alkaline earth-metal ion coordination in different chemical environments have been presented. In metal ion-PEO oligomer ion-pairs the Mg 2+ ion binds strongly to ether oxygens of polyether complexes. The density functional calculations predict the heptaglyme ( n = 7 in the above series) binds strongly to the metal ion. The frequency shifts of characteristics vibrations induced by the metal ion-coordination in CH 3O(CH 2CH 2O) n CH 3-M ( n = 2–7) complexes have been discussed.

Energy materials

Fundamental advances in the solid state chemistry of ionically conducting solids are essential if we are to address the problem of clean energy supply and hence global warming. Several new directions are discussed in this context. Recently, we have synthesised, for the first time, TiO2 nanowires. They possess diameters between 20 and 40 nm and may be up to several microns in length. The crystal structure is that of the less well known polymorph TiO2B. The nanowires are excellent intercalation hosts for Li, reaching a composition of Li0.91TiO2B (corresponding to 305 mAh g−1 of charge stored), almost twice the capacity of anatase. After a small irreversible capacity loss on the first cycle, reversibility of intercalation is excellent. This material is of interest as a potential negative electrode in rechargeable lithium batteries. The first synthesis of ordered mesoporous Fe2O3 materials is described. Two forms, exhibiting respectively pores ordered in 2 and 3 dimensions have been characterised. Metal–polyether complexes (polymer electrolytes), the solid state analogues of the crown ether complexes, are discussed. For some 30 years it was believed that only amorphous lithium-polyether complexes supported ionic conductivity, recently we have shown that this is incorrect. We have reported the first example of crystalline polymer electrolytes supporting ionic conductivity. New developments involving the doping of stoichiometric metal–polyether complexes, specifically PEO6:LiXF6, where X=P,As,Sb, are discussed that enhance the conductivity by up to 2 orders of magnitude.

Ring opening reactions of 1,2-epoxides catalyzed by complexes of polyether ligands with metal halides in low polarity solvents. Comparison with heterogeneous systems

Metal ion electrophilic catalysis has been revealed in ring opening reactions of 1,2-epoxides 1-5 promoted by complexes of polyethers 6-9 with alkali metal halides MHal (M + = Li + , Na + , K + ; Hal - = I - , Br - ) in solvents of low polarity (chlorobenzene, 1,2-dichlorobenzene). The catalytic effect depends on the Lewis acid character of the cation (K + cyclic polyether). Results have been rationalized on the basis of a transition state where the complexed cation (M + ⊂ Lig) stabilizes the negative charge developing on the oxygen atom of the oxirane ring while favors the nucleophilic attack at the adjacent carbon by the halide anion Hal - .

Assessment of the Macrocyclic Effect for the Complexation of Crown‐Ethers with Alkali Cations Using the Substructural Molecular Fragments Method.

The Substructural Molecular Fragments method (Solov'ev, V. P.; Varnek, A. A.; Wipff, G. J. Chem. Inf. Comput. Sci. 2000, 40, 847−858) was applied to assess stability constants (logK) of the complexes of crown-ethers, polyethers, and glymes with Na+, K+, and Cs+ in methanol. One hundred forty-seven computational models including different fragment sets coupled with linear or nonlinear fitting equations were applied for the data sets containing 69 (Na+), 123 (K+), and 31 (Cs+) compounds. To account for the “macrocyclic effect” for crown-ethers, an additional “cyclicity”descriptor was used. “Predicted” stability constants both for macrocyclic compounds and for their open-chain analogues are in good agreement with the experimental data reported earlier and with those studied experimentally in this work. The macrocyclic effect as a function of cation and ligand is quantitatively estimated for all studied crown-ethers.

Assessment of the Macrocyclic Effect for the Complexation of Crown-Ethers with Alkali Cations Using the Substructural Molecular Fragments Method

The Substructural Molecular Fragments method (Solov'ev, V. P.; Varnek, A. A.; Wipff, G. J. Chem. Inf. Comput. Sci. 2000, 40, 847-858) was applied to assess stability constants (logK) of the complexes of crown-ethers, polyethers, and glymes with Na+, K+, and Cs+ in methanol. One hundred forty-seven computational models including different fragment sets coupled with linear or nonlinear fitting equations were applied for the data sets containing 69 (Na+), 123 (K+), and 31 (Cs+) compounds. To account for the "macrocyclic effect" for crown-ethers, an additional "cyclicity"descriptor was used. "Predicted" stability constants both for macrocyclic compounds and for their open-chain analogues are in good agreement with the experimental data reported earlier and with those studied experimentally in this work. The macrocyclic effect as a function of cation and ligand is quantitatively estimated for all studied crown-ethers.

Cation environment in polyether complexes based on poly(tetramethylene glycol) doped with zinc and cobalt chlorides

AbstractX‐ray absorption spectroscopy [extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge structure (XANES)], differential scanning calorimetry, and Raman spectroscopy measurements were performed for a series of liquid polyether/salt systems prepared with poly(tetramethylene glycol) (PTMG) and the copolymer poly(tetramethylene glycol‐co‐ethylene glycol) as matrices and zinc and cobalt chlorides as dopants in the concentration range of n = 30–90, where n is the molar ratio of oxygen to metal cation. According to EXAFS, XANES, and Raman results, even in diluted solutions, these complexes exist mostly as undissociated ZnCl2 and CoCl2 species, presenting a weak cation–polymer interaction. EXAFS results indicate that for polymer/ZnCl2 systems, the nearest metal neighbors are only chlorine atoms. However, for polymer/CoCl2 samples, oxygen is also observed coordinating the metal. Raman spectra do not support any feature related specifically to the cation–polymer interaction. Nevertheless, for both salts the symmetric stretching vibrations are located in frequencies characteristic of salt in solution, which means that the polymer solvating action is effective. Differential scanning calorimetry data show an increase in the glass‐transition temperature for all polymer/salt systems in relation to the pure polymer samples, a consequence of the increase in the macromolecular chain stiffening produced by the presence of the salt. This result corroborates the existence of polymer–salt interactions. © 2001 John Wiley &amp; Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2572–2580, 2001

Atmospheric pressure ion mobility spectrometry studies of cyclic and acyclic polyethers

Cyclic and acyclic polyethers have been analysed by atmospheric pressure ion mobility spectrometry (IMS). The reduced mobilities of gas-phase cyclic polyether ions may be distinguished from their acyclic analogues as a consequence of differences in the collision cross-sections of their adopted conformations. Peaks attributed to polyether/protonated amine complexes are formed when polyethers are introduced in the presence of N-ethylmethylamine, n-propylamine and benzylamine vapour. Variations in the reduced mobilities for the polyether complexes containing isomeric N-ethylmethylamine and n-propylamine guests are associated with small conformational differences for these ions. SYBYL™ molecular modelling software was used to confirm structural characteristics inferred from the experimental mobility data.

Remedying the iron-deficient maize plants grown at lower than the optimal temperature and irradiance by new synthetic macromolecular iron-chelating agents

Summary The efficacy of Fe 3+ complexes of polyethers having chelating terminal 8-quinolinol (8QOH) residues for remedying the iron-deficient maize plants at temperatures of 20/16°C and photosynthetic photon flux density (PPFD) 500-600 μmol m -2 s -1 was evaluated by their effect on the fresh and dry weight, pigment content (total chlorophyll and carotenoids), chlorophyll fluorescence, and photosynthetic activity of maize plants. In order to estimate the effect of the oligomer nature of the polyethers with 8QOH group attached to the oxyethylene chain at different positions of aromatic ring, tests on chlorotic plants were also performed with Fe 3+ complexes of low-molecular-weight ligand 8QOH, and mixtures of commercial polyethers with isopropylamino end-groups (Jeffamines ED) and 8QOH (Jeff/8QOH). The efficacy of Fe 3+ chelates of synthetic chelator ethylenediaminetetraacetic acid and FeCl 3 · 6H 2 O for remedying the chlorotic maize plants under the same conditions was also tested. At temperatures of 20/16 °C and PPFD 500-600 1J.mol m-2 s-1 , the Fe3+ chelates of polymers with 8QOH groups attached at 5-position were the most effective for remedying the iron-deficient maize plants compared to the other tested Fe 3+ complexes. It was found that the plant remedy process was sensitive to lowering of the temperature and PPFD. The remedy of chlorotic maize plants supplied with investigated Fe 3+ complexes at 20/16 °C (day/night) and PPFD 500-600 μmol m -2 s -1 retarded 4-fold compared to that observed at 30/25 °C and PPFD 1100-1300 μmol m -2 s -1 . We concluded that the longer period for remedying the iron-deficient maize plants at lower than the optimal temperature and PPFD is probably due to the fact that, under these conditions, the amount of DMA released from roots is several times lower, and the efficiency of the high-affinity system for uptake of Fe 3+ -PS is decreased as compared to that at optimal temperature and PPFD.