Acyclic Polyethers Research Articles

Stability of 1-naphthalenediazonium ion in solution. Complexation and decomposition of 1-naphthalene- diazonium tetrafluoroborate in the presence of crown ethers and acyclic polyethers in 1,2-dichloroethane and the gas phase under fast atom bombardment conditions

The effects of solvent, temperature and pH on the rate of decomposition of uncomplexed 1-naphthalenediazonium tetrafluoroborate were studied by UV spectrometry. The complexation of the 1-naphthalenediazonium ion with crown ethers containing 4–10 oxygen atoms and some acyclic polyethers was detected and characterized in the gas phase by fast atom bombardment mass spectrometry (FAB-MS). In addition, the host–guest complexation and the kinetics of the thermal dediazoniation of 1-naphthalenediazonium ion in the presence of four crown ethers and two acyclic polyethers were studied in 1,2-dichloroethane (DCE) solution at 40 °C by UV spectrometry. All hosts, except 12-crown-4, formed 1:1 complexes under FAB conditions. The values of the thermodynamic stability K and the stabilizing ability of the complexation (k2/k1) in DCE were calculated from the kinetic data. The thermodynamic and kinetic stabilities were observed to be greater for the inclusion complex of the­1-naphthalenediazonium ion formed with crown ethers containing at least six oxygen atoms than for the non-spesific adduct formation formed with 15-crown-5. This was also true for tetraglyme, whose chain is too short to be capable of being fully wrapped around the diazonium group as in the complex of PEG 1000. Crown ethers with seven oxygen atoms are the strongest complexing agents for all the aromatic diazonium ions studied, for the 1-naphthal-enediazonium ion investigated here and for arenediazonium ions examined earlier. The values of the activation enthalpy ΔH≠ for the thermal dediazoniation of the uncomplexed salt in both the acidic aqueous solution and DCE were observed to be high, and the corresponding values of activation entropy ΔS ≠ were clearly positive. The results are consistent with a heterolytic SN1-like mechanism involving the decomposition of the uncomplexed and complexed 1-naphthalenediazonium ion into a highly reactive naphthyl cation, followed by fast product-determining reactions with nucleophiles to give the products. Copyright © 2000 John Wiley & Sons, Ltd.

Metal ion complexation by acyclic polyethers with lipophilic amide, thioamide, and amine end groups

A series of acyclic polyethers with lipophilic amide, thioamide, and amine end groups was synthesized. Metal ion transport across bulk liquid membranes and measurement of thermodynamic parameters for ligand-metal ion complexation by titration calorimetry show strong selectivity for complexation of lead ion over other metal ion species for the diamide ligand. Lead ion complexation by the acyclic polyether diamide involves the amide oxygens and silver ion coordination by a dithioamide analog involves the thioamide sulfurs. With a proper length of the ethereal linkage, the ligand wraps around the metal ion in a pseudocyclic fashion.

Synthesis and Characterization of Novel Acyclic Polyethers Containing Two Tetrahedral Cluster Moieties as Terminal Groups

Five novel acyclic cluster polyethers η5-C5H4CH2(CH2OCH2) nCH2C5H4-η5][MFeCoS(CO)8]2(M = Mo, W; n = 2,3; M = Mo, n = 4) are synthesized through double isolobal displacement reaction of (μ3-S)FeCo2(CO)9 with [η5-C5H4CH2(CH2OCH2) nCH2C5H4-η5][(CO)3MNa]2 and characterized by elemental analysis and spectroscopic techniques.

Synthesis of new lipophilic acyclic di-ionizable polyethers, bis(crown ethers) and macrocyclic diamides

A series of new lipophilic acyclic polyethers containing two carboxylic or hydroxamic acid groups have been prepared. From lipophilic acyclic polyether dicarboxylic acids 2, 9 and 13, the bis(crown ethers) 20–25 were synthesized. From lipophilic acyclic polyether dicarboxylic acids 10–12 and 14, the new macrocyclic diamides 26–32 were prepared in high yields without the use of high dilution techniques or template effects.

Pseudorotaxanes and Catenanes Containing a Redox-Active Unit Derived from Tetrathiafulvalene

Two bis(2-oxy-1,3-propylenedithio)tetrathiafulvalene-containing acyclic polyethers and two macrocyclic polyethers, each incorporating one bis(2-oxy-1,3-propylenedithio)tetrathiafulvalene unit and one p-phenylene ring, have been synthesized. The two acyclic polyethers are bound by cyclobis(paraquat-p-phenylene) with pseudorotaxane geometries in solution. The two macrocyclic polyethers have been mechanically interlocked with this tetracationic cyclophane to form [2]catenanes in a kinetically controlled self-assembly process. The X-ray crystallographic analysis of one of the two [2]catenanes and 1H-NMR-spectroscopic studies of both compounds showed that the p-phenylene ring of the macrocyclic polyether is located inside the cavity of the tetracationic cyclophane, while the bis(2-oxy-1,3-propylenedithio)tetrathiafulvalene unit resides alongside. The [2]pseudorotaxanes and [2]catenanes show broad bands around 780 nm, arising from the charge-transfer (CT) interaction between the electron-donor tetrathiafulvalene-(TTF-)type unit and the electron-acceptor units of the tetracationic cyclophane. 1H-NMR-spectroscopic studies have shown that the [2]pseudorotaxanes dissociate into their separate components upon oxidation of the TTF-type unit, as a result of disruption of the CT interaction and electrostatic repulsion between the tetracationic host and the newly formed monocationic guest. The subsequent reduction of the guest to its neutral state affords back the pseudorotaxane-type complex restoring the original equilibrium. The results obtained from electrochemical experiments are consistent with the reversible, redox-driven dethreading/rethreading process observed by 1H-NMR spectroscopy. Variable-temperature 1H-NMR-spectroscopic investigations have revealed two dynamic processes, both involving the relative movements of the mechanically interlocked components in the [2]catenanes. The two consecutive oxidation processes involving the TTF-type unit, observed electrochemically, are displaced toward more positive potentials compared with the free cyclic polyethers. The two reversible two-electron reduction processes, characteristic of free cyclobis(paraquat-p-phenylene), separate into four reversible one-electron processes because of the topological difference between the “inside” and “alongside” electron-acceptor units in the [2]catenane.

Synthesis and Characterization of Novel Acyclic Polyethers Containing Two Tetrahedral Cluster Moieties as Terminal Groups

Five novel acyclic cluster polyethers [η5-C5H4CH2(CH2OCH2)nCH2C5H4-η5][MFeCoS(CO)8]2 (M=Mo, W; n=2,3; M=Mo, n=4) are synthesized through double isolobal displacement reaction of (µ3-S)FeCo2(CO)9 with [η5-C5H4CH2(CH2OCH2)nCH2C5H4-η5][(CO)3MNa]2 and characterized by elemental analysis and spectroscopic techniques.

Synthesis of Acyclic Polyethers Bearing Thioamide End-Groups and Selective Sensing of Silver Ion

A series of acyclic polyethers bearing thioamide end-groups and lipophilic alkyl chains were successfully synthesized with moderate yields. Transport measurements in a bulk liquid membrane (BLM) system indicated a very high selectivity of silver ion over other metal cations. Thermodynamic parameters (ΔH, TΔS, and log K) for ligand-metal ion complexations were determined by solution calorimetric titration in methanol at 25 °C. The complexations were enthalpy driven and silver ion exhibited a high selectivity over other metal ions due to the increase of covalent binding between the soft acid (Ag+) and soft base (sulfur).

Selective Recognition of Calcium Ion through Liquid Membrane

The mole transport rate of alkaline earth metal ions through a bulk liquid membrane and a supported liquid membrane using a series of proton diionizable acyclic polyethers was measured. Among alkaline earth metal ions, the calcium ion was observed to be selectively transported in both single and competitive transport experiments. Potentiometric titration and solution calorimetric titration also gave calcium selectivity over other alkaline earth metal ions. Acyclic polyether bearing a diethylene glycol unit andn-tetradecyl lipophilic chain at the α position of carboxylic acid affords the best selectivity for the calcium ion in bulk and supported liquid membranes.

ChemInform Abstract: Selective Transport of Pb(II) Ion by Acyclic Polyethers Bearing Amide End‐Groups.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Constitutionally Asymmetric and Chiral [2]Pseudorotaxanes1

The self-assembly and characterization of a range of chiral pseudorotaxanes has been explored using chiroptical methods. The syntheses of constitutionally asym. acyclic hydroquinone-contg. polyethers and optically active hydroquinone-contg. acyclic polyethers, bearing a couple of Me or iso-Bu groups related to each other in a C2-sym. manner within the polyether backbone, are described. The combination of the tetracationic cyclophane cyclobis(paraquat-p-phenylene) tetrakis(hexafluorophosphate), possessing a p-electron deficient cavity, and the linear noncentrosym. acyclic polyethers produces [2]pseudorotaxanes that have been characterized by 1H NMR, UV/vis and CD spectroscopies in soln. and X-ray crystallog. in the solid state. The introduction of constitutional asymmetry or chirality gives rise to a no. of different geometries for the [2]pseudorotaxanes in both the soln. and solid states. In particular, CD-spectroscopic measurements on the optically active [2]pseudorotaxanes have shown that - depending on the positions of the C2 sym. related chiral centers in the polyether chains with respect to the hydroquinone rings - the chirality present in the p-electron rich threadlike guest can induce chirality that is assocd. with the supramol. structure as a whole, resulting in a chiral charge-transfer transition involving not only the p-donors in the chiral guests but also the p-acceptors in the achiral host.

Silver(I)-selective membrane electrodes based on sulfur-containing podands

Some podands, acyclic polyethers, were utilized as membrane active components to prepare Ag +-selective polymeric membrane electrodes. The thiapodand-based electrodes exhibited considerable selectivity toward Ag + over other heavy metal ions including Cd 2+, Pb 2+, Cu 2+ and Hg 2+. Also, good selectivity over alkali and alkali earth metal ions were observed. Response slopes, pH effects, response time, and signal baseline return of the sensor systems were studied in static mode and/or in a flow-injection system. The Ag +-selectivity was explained by the soft-soft interaction of the Ag + ion with the sulfur donor atoms as well as the stacking interaction between aromatic end groups of the host molecule on complexation.

Potentiometric Responses of Ionophore-Incorporated Bilayer Lipid Membranes with and without Added Anionic Sites

Potentiometric behaviors of bilayer lipid membranes (BLMs) incorporated with such ionophores as valinomycin, crown ethers and acyclic polyethers were described for various alkali and alkaline earth metal ions. The ionophores were directly incorporated into planar BLMs formed by the folding method. Among seven kinds of ionophores examined, only the valinomycin- and ETH 4120-based BLMs generated potentiometric Nernstian responses. However, simultaneous incorporation of anionic sites, such as sodium tetrakis[3, 5-bis(trifluoromethyl)phenyl]borate (NaTFPB) or potassium tetrakis(4-chlorophenyl)borate (KTpClPB), was found generally effective for inducing potentiometric Nernstian responses of the ionophore-based BLMs. The added anionic sites were also found to decrease the membrane resistance, leading to improvement of probability of potential measurements, and to lower the detection limits by maintaining Nernstian slopes, thereby providing a basis for quantitative BLM sensors. By comparing the potentiometric responses of ionophore-incorporated BLMs with and without added anionic sites, the role and significance of the anionic sites in potentiometric response of BLMs based on ionophores was discussed.

ChemInform Abstract: Novel Acyclic Polyethers Bearing Amide End‐Groups and Their Complexation Studies in ISE.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Collisionally Activated Dissociation of Transition Metal Ion/Polyether Complexes in a Quadrupole Ion Trap

For a series of polyether/transition metal ion complexes, collisionally activated dissociation reactions that are mediated by the flexibility of the polyether and the number of coordination sites are reported. The metal ions are generated by a pulsed laser desorption technique, and collision-activated dissociation methods are used to characterize the structures of the resulting metal/polyether complexes. The CAD patterns for the different polyether/metal ion complexes show striking variations depending on the flexibility of the ether, its number of coordination sites, and the type of metal ion. For example, (18-crown-6 + Co+) dissociates by loss of CHCH• or C2H3O• radicals, each pathway in conjunction with multiple losses of C2H4O, and resulting in products incorporating one covalent or ionic bond between the Co+ ion and the crown ether. In contrast, (12-crown-4 + Co+) dissociates by loss of CH2CH2 or C2H4O closed shell neutrals, each pathway in conjunction with additional losses of C2H4O and resulting in products that incorporate no covalent bonds to Co+. The polyether/Ni+ complexes show dissociation behavior that is similar to that observed for the Co+ complexes, but the polyether/Cu+ complexes show uniform dissociation trends that seem to be independent of the flexibility and number of coordination sites of the ether. These differences are rationalized based on the nature of the metal ion, and both the flexibility of the crown ether and its number of coordinating sites, factors which affect the geometry during coordination of the metal ion. This idea is supported by comparative dissociation reactions of metal complexes containing acyclic polyethers (glymes) which have more flexible structures. MS/MS/MS experiments and CAD of complexes formed by model compounds offer support for the dissociation mechanisms.

ChemInform Abstract: Solvent Extraction of Transition Metal Ions with Acyclic Polyethers Incorporating Several Heteroatoms and Bearing Heterocyclic Moieties as End Groups.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Complexation of tropylium ions with crown ethers and acyclic polyethers examined by fast atom bombardment mass spectrometry

AbstractThe molecular complex formation of six macrocyclic and six acyclic polyethers with tropylium and 4‐methoxyphenyltropylium tetrafluoroborates was observed and characterized in the gas phase by fast atom bombardment mass spectrometry (FABMS), to obtain information on intrinsic molecular interactions in the absence of the complicating effect of solvation. The stoichiometry of the complexes was assessed on the basis of corresponding peaks in FAB mass spectra. In addition to the expected 1 : 1 complexes between polyether and tropylium ion, some 2 : 1 complexes were also formed. The stability order of selected complexes was studied in competition experiments. The complexation equilibrium constant and thermodynamic parameters for the interaction of dibenzo‐18‐crown‐6 with tropylium ion were determined in 1,2‐dichloroethane solution by UV‐visible spectrophotometry. Complexation of polyethers with tropylium salts has not been reported previously.

Solvent Extraction of Transition Metal Ions with Acyclic Polyethers Incorporating Several Heteroatoms and Bearing Heterocyclic Moieties as End Groups

Abstract Nine acyclic polyethers incorporating oxygen, nitrogen and/or sulfur atoms were synthesized, which possess two heterocyclic groups at both ends of an ether chain, and metal ion extractabilities of these compounds were estimated using 1,2-dichloroethane - H2O system. On the solvent extraction of some transition metal ions as the nitrates, Ag+, Cu+ and Hg2+ were more effectively extracted with most of the reagents than the other metal ions. Addition of picrate ion into the aqueous phase of AgNO3 increased Ag+ extractability remarkably.

Complexation and Decomposition of Benzenediazonium Tetrafluoroborate in the Presence of Acyclic Polyethers in 1,2-Dichloroethane and in the Gas Phase.

Complexation and Decomposition of Benzenediazonium Tetrafluoroborate in the Presence of Acyclic Polyethers in 1,2-Dichloroethane and in the Gas Phase.

Effect of Solvent on the Complexation and Dediazoniation of Benzenediazonium Tetrafluoroborate in the Presence of Acyclic Polyethers.

Effect of Solvent on the Complexation and Dediazoniation of Benzenediazonium Tetrafluoroborate in the Presence of Acyclic Polyethers.

Precipitation of strong uncharged organic acids with various crown ethers or with acyclic polyethers from aqueous medium. Characterization of adducts in the solid state

AbstractIt was found that substituted picric acids form slightly soluble 1 : 2 : 2 adducts with several simple crown ethers or with tri‐, tetra‐, or pentaethylene glycol dimethyl ether (glymes 4, 5 and 6) in water, whereas 2,4,6‐trinitrobenzenesulfonic acid forms a 1 : 1 : 1 adduct with dicyclohexano‐18‐crown‐6 (cis‐syn‐cis). The ability of a crown ether to precipitate a given acid follows the order dicyclohexano‐18‐crown‐6 (cis‐syn‐cis) > benzo‐15‐crown‐5 > dicyclohexano‐24‐crown‐8 > 18‐crown‐6 > 21‐crown‐7, 15‐crown‐5 ≫ 12‐crown‐4, roughly in the order of its base strength. Precipitation can occur even when the concentration(s) of one or more of the components are < 10−4 M. The solubility products of the 18‐crown‐6 complexes with dichloro‐ or dimethylpicric acids were estimated. In the solid state the 1 : 2 : 2 dicyclohexano‐18‐crown‐6 (cis‐anti‐cis)–dichloropicric acid–water complex, which reportedly has two pseudohydronium ions lacking C3v symmetry of H3O+, exhibits an IR spectrum in the OH stretching region characteristic of an aqua complex.