Iodide Counterions Research Articles

Sodium cation complexation in a macrocycle containing thymines as sidearm donor groups

Previous studies of macrocycles having alkyl sidearms terminated in adenine or thymine have been focused on intermolecular association. Electrospray mass spectrometric analyses suggested that sodium complexation could be a major alternative process in the presence of the appropriate cation. Sodium cation complexation by N,N′-bis(3-(1-thyminyl)propyl)-4,13-diaza-18-crown-6 has been confirmed by X-ray crystallographic analysis. A sodium cation is bound in the center of the macroring. The four ether oxygens and two thyminyl carbonyl donors have the shortest contacts with the two, macroring nitrogen atoms being somewhat more remote. Neither the iodide counterion nor an acetone of solvation appears to interact with the sodium cation. Crystal Data: Triclinic, \(P_{\bar 1} \) , a = 11.9371(12), b = 12.1588(13), c = 13.7885(14) A, α = 78.083(2)°, β = 83.213(2)°, γ = 78.997(2)°, and Dcalc = 1.392 g cm−3, Z = 2.

Facile, Novel Methodology for the Synthesis of Spiro[pyrrolidin-3,3′-oxindoles]: Catalyzed Ring Expansion Reactions of Cyclopropanes by Aldimines

The role of the bifunctional catalyst is decisive: The magnesium ion as Lewis acid and its nucleophilic iodide counterion contribute in synergy to the successful ring expansion of the cyclopropane 1 by aldimine 2 [Eq. (1)]. This reaction offers a novel route to spiro[pyrrolidin-3,3'-oxindoles] 3.

Facile, Novel Methodology for the Synthesis of Spiro[pyrrolidin-3,3′-oxindoles]: Catalyzed Ring Expansion Reactions of Cyclopropanes by Aldimines

The role of the bifunctional catalyst is decisive: The magnesium ion as Lewis acid and its nucleophilic iodide counterion contribute in synergy to the successful ring expansion of the cyclopropane 1 by aldimine 2 [Eq. (1)]. This reaction offers a novel route to spiro[pyrrolidin-3,3'-oxindoles] 3.

Voltammetrische Charakterisierung des elektrochemischen Redoxverhaltens von N-Thiocarbamoyl-benzamidinen und 1,2,4-Thiadiazoliumsalzen

The electrochemical redox behaviour of N-(diethylamino-thiocarbamoyl)-benzamidines Et2N-C(S)-N*C-(NHR)-Ph (1: R=H; 2: R=n-C3H7; 3: R=Ph) and 2,3-diphenyl-5-diethylamino-1,2,4-thiadiazolium iodide (4) as well as of its perchlorate (5) was studied by cyclic voltammetry in ethanolic solution at a glassy carbon electrode between −1.2 V and +1.5 V vs. Ag/AgCl. The mechanisms for the irreversible anodic oxidation of the benzamidines 1–3 and the formed products (1,2,4-thiadiazolium cations or 1,2,4-thiadiazole) are influenced directly by the substituents bound to the terminal benzamidine nitrogen atom. In the cathodic potential range, an irreversible reductive cleavage of the benzamidines 1–3 occurs which also depends on the N-bound substituents. The products of this reduction, which are identified indirectly electrochemically by comparing voltammogramms, can be adsorbed on the electrode surface and reoxidized in the following anodic scan. The 1,2,4-thiadiazolium cation of 4 and 5 is redox inert in the investigated anodic potential range. The obtained anodic peaks in the case of 4 result from redox reactions of the iodide counter ions only. However, the 1,2,4-thiadiazolium cation is also subject of a reductive cleavage in a similar way to the mechanism which is proposed for the N-thiocarbamoyl-benzamidines 1–3. The discussed electrochemical redox mechanisms of the characterized compounds 1–5 are compatible with known results of synthesis.

1,3-Diamino-5-ammonio-1,3,5-trideoxy-cis-inositol iodide

The cation in 1,3-diamino-5-ammonio-1,3,5-trideoxycis-inositol iodide (HtaciI, C 6 H 16 N 3 O 3 + .I - ) adopts a chair conformation with the three N atoms in equatorial positions and the three O atoms in axial positions. The Htaci + cation displays an intramolecular O-H…O hydrogen bond. A complex network of N-H…O and O-H…N hydrogen bonds generates a complex structure with channels along [001] which are filled with the iodide counter-ions coordinated by N-H…I hydrogen bonds.

Two-Dimensional Pigment Monolayer Assemblies for Light-Harvesting Applications: Structural Characterization at the Air/Water Interface with X-ray Specular Reflectivity and on Solid Substrates by Optical Absorption Spectroscopy

X-ray specular reflectivity at the liquid/gas interface of dihexadecyl phosphate (DHDP) on pure H2O and on a series of pigment-containing aqueous solutions are reported along with visible absorption spectra of corresponding monomolecular Langmuir−Blodgett films on quartz substrates. Molecular level interpretation of the reflectivity from DHDP on pure water reveals that at large surface pressure (>10 mN/m), the film is closely packed with practically untilted hydrocarbon chains and hydrated phosphate headgroups. On solutions containing either water-soluble cationic tetraazaphthalocyanines or tetrapyridylporphyrins, significant changes in the organization of the lipid with respect to that on pure water are found. Total film thicknesses are larger and consistent with the adsorption of a single pigment layer contiguous to the headgroup, whereas the hydrocarbon tail region is shorter, suggestive of tilted alkyl chains. In addition, film thicknesses for phthalocyanine-containing films suggest formation of an iodide counterion layer underneath the plane containing the pigments. This sharply contrasts the interfacial profile obtained for porphyrin-containing films, in which the iodide counterions appear to exist within the pigment plane. Visible absorption spectra of all transferred films indicate a closely packed single pigment layer, consistent with the reflectivity results. The optical spectra of the pigment are preserved (in relation to the aqueous solution monomer spectra) in the transferred film, indicating a suppression of pigment aggregation. Reflectivity measurements at large molecular areas on pure water indicate that DHDP forms an inhomogeneous film, suggestive of phase segregation; on the pigment-containing solutions, DHDP induces (through attractive Coulomb interactions) the adsorption of a homogeneous monopigment layer. The existence of a complete pigment monolayer over the measured surface pressure−molecular area (π−A) isotherms has been evidenced by both X-ray reflectivity and visible optical studies. Preservation of pigment functionality has been demonstrated through the process of Coulomb association of the chromophores with charged lipid monolayer headgroups at the air/water interface. The potential for applications as model photosynthetic antennae will be discussed.

Caesium Iodide Complex of 1,3-Calix[4]-bis-crown-6

In [13,16,19,22,25,28,42,45,48,51,54,57-dodecaoxahexaheptacyclo[28.28.1.111,40.05,58.07,12.029,34.036,41]hexaconta-1(58),2,4,7,9,11,29,31,33,36,38,40-dodecaene-1κ6O; 2κ6O]bis(iodocaesium) bis(acetonitrile) solvate, [Cs2I2(C48H60O12)].2CH3CN, the calix[4]arene macrocycle, fixed in the 1,3-alternate conformation by two bridging –(OCH2CH2)5O– units (denoted 1,3-calix[4]-bis-crown-6) forms a binuclear complex with caesium iodide. The two Cs+ ions are located at the centre of the coordination site defined by the six O atoms of a crown-ether chain and are bonded to six O atoms and iodide counterions; they also interact with the two closest benzene rings. This complex is isostructural with the previously reported structures of `free' 1,3-calix[4]bis-crown-6 and some of its complexes with caesium or potassium nitrate.

Aluminum Chloride–Tetraalkylammonium Halide Complex as a Novel Catalyst in Friedel–Crafts Alkylation. Direct Construction of the Chroman Structure from 1,3-Diene

Abstract Tetrabutylammonium halides were found to accelerate Lewis acid-catalyzed Friedel–Crafts alkylation when trimethylhydroquinone and myrcene were used, followed by cyclization to give the chroman compound predominantly. For tetraalkylammonium salts which have long-chain alkyls and/or bromide, iodide counter anions promote the reaction in less-polar solvents. Phosphonium halides and sulfonium halide were also effective. The tetraoctylammonium bromide–aluminum chloride complex was an effective catalyst for the initial regioselective protonation of 7,11,15-trimethyl-3-methylene-1,6-hexadecadiene to give α-tocopherol in high yield.

Influence of the functionality of the quaternizing agent and the polymer molecular weight on the viscoelastic behaviour of α,ω-(dimethylamino)polyisoprenes

Quaternization of the end-groups of α,ω-(dimethylamino)polyisoprenes with monofunctional, difunctional and trifunctional halides (iodides and bromides) has been undertaken on polymers of different molecular weights ( M n =6000 and 38000 g mol −1 ). The thermal stability of the ammonium end-groups is somewhat better when iodide counteranions are present. Quaternization increases the T g of the material. This effect is more pronounced for low molecular weight chains, especially when a short alkyl group quaternizing agent is used. However, the size of the alkyl or aryl radical has a minor effect on polymer T g when difunctional quaternizing agents are used. Nevertheless, the modulus of the rubber-like plateau of materials with difunctional agents is higher than with monofunctional quaternizing agents, owing to coupling reactions between the chain-ends. Rheological measurements indicate that the quaternized low molecular weight polyisoprenes exhibit an Arrhenius-type temperature dependence characterized by activation energies which vary between 121 and 146 kJ mol −1 and suggest that the relaxations attributed to dipole—dipole interactions dominate over long chain entanglements.

Nucleophilic Attack on 4,5-Dihydro-4-alkyl-3H-dinaphtho[2,1-c:1',2'-e]thiepinium Salts. A Convenient Approach to New 2,2'-Bidentate 1,1'-Binaphthalene Ligands with Sulfur Donor Atoms

The title dihydrothiepinium salts (6) react with a wide range of N-, S-, Se-, O-, and C-nucleophiles to afford dihydrothiepin (5) and/or the corresponding bidentate ligands (7). The dual course of the reaction can be controlled by a judicious choice of the substrate counterion. In most instances, an iodide counterion aids formation of dihydrothiepins (5), whereas perchlorate, tetraphenyl borate, or tetrafluoroborate coun- terions favor formation of bidentate ligands (7). An explanation based on a competition between the counterion and the external nucleophile is provided. Dihydrothiepinium salts (6) are easily accessible from dibro- mide (R,S)-(4) via dihydrothiepin (R,S)-5. Individual enantiomers (R)- and (S)-(5) have been obtained by resolution on a preparative triace- tylcellulose (TAC) column ans assigned absolute configuration on the basis of CD spectra and chemical correlation

The two solid-state conformations of nefopam methiodide, a quaternary ammonium salt of the analgesic drug

The solid-state structure of nefopam methiodide, a quaternary ammonium salt of nefopam hydrochloride (a non-narcotic analgesic drug), has been determined by single crystal X-ray diffraction analysis. Nefopam methiodide gives crystals belonging to the monoclinic P21/c space group and, at 298 K, a = 10.001(1), b = 9.928(1), c = 17.598(1) Å, β = 94.41(1)°, V = 1742.2(2) Å3, Z = 4, R(F) = 0.086, and Rw(F) = 0.108. Due to disorder, the boat (flattened chair) and twist-chair (flattened chair) conformations of the 2,5-benzoxazocine eight-membered ring were both observed in the crystal with 55:45 occupancy, respectively. Positional disorder was also observed for the iodide counterion, which showed occupancies of 81:9.5:9.5. Keywords: nefopam, analgesic, X-ray crystallography, conformation.

The extraction and analysis of quaternary ammonium compounds in biological material by GC and GC/MS.

An injection port pyrolysis method for the analysis of quaternary ammonium compounds is reported. Identification and confirmation of the analyte was accomplished by gas chromatography/mass spectrometry. With minor modifications to pH used and solvent composition, a common ion-pair method of extraction of quaternary ammonium compounds from biological matrices with an iodide counter ion is described. Although the combined extraction-identification methodology was limited to neostigmine, succinylcholine, and paraquat, it should easily be applicable to any of the other compounds examined in this study.

Studies on a General Method for the Demethylation of Quaternized Nitrogen Heterocycles

Abstract Probably the best general method so far developed for the dealkylation of quaternized nitrogen heterocycles is the reaction of the iodide salts in an aprotic solvent in the presence of triphenylphosphine.1,2 It has since been established3 that the iodide counterion is the active dealkylating agent, with the triphenylphosphine acting as a “methyl sponge”, preventing the reverse reaction from occurring. It follows, therefore, that any heterocycle (1) ought to be able to fulfil the same role as the triphenylphosphine with respect to the dealkylation of the quaternary salt of a less nucleophilic heterocycle (2). Since the reactivity to methylation of a large number of heterocycles with a reactivity range of ca 106 is known4, the choice of a convenient heterocycle (1) to go with any heterocycle (2) is, in principle, a wide one.

Salt effects on the critical micellar concentration, iodide counterion binding, and surface micropolarity of 1-methyl-4-dodecylpyridinium iodide micelles

Salt effects on the critical micellar concentration, iodide counterion binding, and surface micropolarity of 1-methyl-4-dodecylpyridinium iodide micelles

Reversible crosslinking in cellulose. VI. Formation of sulfonium derivatives by the reaction of cellulose β-mercaptoethylaminocarboxylate with methyl iodide

The reaction of methyl iodide with cellulose β-mercaptoethylaminocarboxylate (RDTC) made from cotton was investigated. The product was found to contain dimethyl sulfonium groups in addition to S-methyl groups, with accompanying hydrolytic cleavage of some of urethane linkages. The iodide counterions could be easily exchanged with hydroxide and chloride ions. The dyeabilty of RDTC and its sulfonium derivatives toward Direct Sky Blue A was studied. The equilibrium uptake of the dye by RDTC decreased with increasing sulfur content, while the uptake by the sulfonium derivatives was higher than that of control cotton and increased with increasing sulfonium content. The counterions did not affect the dyeability. The dye adsorbed onto the sulfonium derivatives was very fast against solvent extraction, and could be extracted only with Cadoxen containing 0.5% sodium hydroxide. The equilibrium uptake of the dye was much more than the amount calculated on basis of the 1 : 1 ionic bonding between the sulfonic acid group in the dye molecule and the sulfonium group in the modified cotton. The spatial effect in the dye–sulfonium bonding is discussed.

Attenuation of 5.9-keV Photons by Helium and Hydrogen

The narrow-beam mass-attenuation coefficients of helium and hydrogen were measured at 5.895 keV. A Kβ-filtered 55Fe source of Mn x rays, a set of collimators, and a low-energy sodium iodide counter were used with a high-pressure gas chamber. Photon intensities were measured with and without gas in the chamber. The measured coefficients are 0.416±0.017 cm2/g for He and 0.400±0.016 cm2/g for H2. These numbers are compared with theoretical predictions of this parameter.

Attenuation of 5.9 keV Photons by Air

The narrow beam attenuation coefficient of air was measured at 5.895 keV. An 55Fe source of Mn x rays with a CrKβ filter and a collimated low-energy sodium iodide counter were used. The photon intensity as a function of the source-detector distance was determined in vacuum and in atmospheric air. The value of the measured coefficient is 24.55±0.25 cm2/g.