Tetraethylammonium Cations Research Articles

Voltammetric study of ion transfer across the water/ o-nitrophenyloctyl ether interface : Part I. Reversible process

A new method for the determination of the zero of the potential scale based on Parker's TATB assumption is proposed. It was determined from the potential sweep voltammogram of tetraphenyl-arsonium tetraphenylborate dissolved in the oil phase, in the present case, in o-nitrophenyloctyl ether (NPOE). The half-wave potentials of ions transfer across the water/NPOE interface were found using voltammetry at ITIES. The conditional Gibbs energies of transfer from water to NPOE for tetramethyl-ammonium and tetraethylammonium cations and for picrate and perchlorate anions were evaluated. The general decrease of these values is due partly to ion-pair formation in the oil phase.

Additivity of theHammett reaction constants ion pairs effect in the polarographic reduction of nitrobenzene and 9,10-anthraquinone derivatives

An attempt has been made to estimate the effect of the subsequent ion pairs formation on the value of theHammett reaction constant measured polarographically. To this purpose, the reduction ofpara-substituted nitrobenzenes and 2-substituted 9,10-anthraquinones was studied at a dropping mercury electrode in N,N-dimethylformamide. The ion pairs reaction constant of substituted nitrobenzene radical anions with tetraethylammonium cations is equal to −1.49 V/σ unit. The corresponding reaction constant for the semiquinone—Li+ series was estimated to be −0.90 V/σ unit. The method of calculation was based on the additivity rule withinHammett's treatment.

Physicochemical characterization of zeolite ZSM-20

Zeolite ZSM-20 is a silica-rich zeolite, possessing a faujasite-like character but having a hexagonal symmetry unit cell. It is synthesized in the presence of tetraethylammonium (TEA) cations as organic directing agents. Those act as counterions, in addition to Na+ cations, and are eventually occluded in the zeolite large cages where the electric field gradient is small.

The effect of tetraethylammonium cation adsorption on the pzc of the mercury—perchloric acid interphase

The acid activity dependence of pzc for the mercury—perchloric acid aqueous solution interphase was studied, and the results compared with previously reported values. Then, the pzc shift caused by tetraethylammonium (TEA) perchlorate addition to constant activity perchloric acid solutions is reported, and an expression for the Esin—Markov coefficient is given. The need for using activity values is discussed on the basis of quantitive data.

SOME PALLADIUM(II) COMPLEXES OF 1,2-BIS(MERCAPTO)ORTHOCARBORANE

Abstract Coordination compounds of the type Pd(DMC)L and [Pd(DMC)2]C where DMC is 1,2-bis(mercapto)-o- carborane, L = 1-diphenylphosphino-o-carborane (HPC), 1,2-bis(diphenylphosphino-o-carborane (NPC) and C [dbnd] H+ or tetraethylammonium cation, have been prepared and characterized by IR, Raman and electronic spectroscopy, magnetic and conductivity measurements. DMC behaves as a bidentate sulphur donor ligand and the tertiary phosphine (HPC) and ditertiary phosphines (DPC and NPC) are bonded through the phosphorous atoms to produce a planar PdS2P2 skeleton of C2v symmetry.

Potassium channels in Eremosphaera viridis

To characterize the assumed potassium channels in the plasma membrane of the green alga Eremosphaera viridis (Köhler et al. 1985), current-voltage (I/V)-curves under resting conditions and during an action-potential-like response (CAP) were constructed using voltage- and current-clamp techniques. Under resting conditions the I/V-curves of Eremosphaera showed a distinct upward bending when approaching zero mV, a nearly straight line in the medium part and a downward bending during strong hyperpolarization. Measurements in light and darkness frequently displayed a parallel shift of the I/V-curve in the middle part, indicating a current source which is slowed down by light-off. Using the voltage-clamp technique, N-shaped I/V-curves were sometimes observed. The potassium concentration outside influenced the downward-bending part of the I/V-curve whereas the tetraethylammonium cation, known to block potassium channels, reduced the upward-bending part in particular. A change in external pH, either to pH 7 or pH 3.1 from a standard pH 5.5, caused an increase in conductivity. Chemically induced action potentials were released in Eremosphaera under voltage-clamp conditions by light-off and there was both a current flow and an increase in conductivity during the CAP. Clamping the membrane potential at a value more negative than Nernst potential of potassium revealed an inward current, whereas clamping at a more-positive value revealed an outward current. The experiments demonstrate that there is no threshold potential in releasing a CAP. The I/V-curves performed under current clamp at the peak of CAP verify a previously found increased conductivity with hyper- or depolarization depending on the external potassium concentration. These experiments provide further evidence that in Eremosphaera potassium channels are involved in the CAP caused by a light-off signal. Additional experiments indicate that after light-off a transient acidification of the cytoplasm takes place in correlation with the CAP and the opening of potassium channels. A preliminary "battery model" is discussed to understand the role of potassium channels during a CAP in pH-regulation of the cytoplasm.

Differential capacity curves at adsorption of organic ions: Model approach II

The Alekseev-Popov-Kolotyrkin model of the electrical double layer has been analyzed for the quantitative description of the adsorption of molecules and tetraalkylammonium ions on electrodes. It has been shown that the model considered satisfactorily can be used for the semi-quantitative description of the adsorption of tetrabutyl- and tetraethylammonium cations and of the diffuse layr effects on the bismuth and mercury electrodes observed in the capacity measurements in aqueous solutions.

RESEARCH ON TRINUCLEAR MOLYBDENUM CLUSTER COMPOUNDS——CRYSTAL AND MOLECULAR STRUCTURE OF (Et_4N)_2[Mo 3 (μ 3 -O)(μ 3 -Cl)(μ 2 -Cl) 3 Cl 6 ]·EtOH

The title crystal belongs to the monoclinic system. The space group is P2_1/c with unit cell parameters: a=11.379(3), b=20.766(2), c=14.487(3), β=91.49(2)°, V=3519(2)~3Z=4, D_c=1.819g.cm~(-3), D_0=1.81g.cm~(-3). The crystal structure was solved by the heavy atom method and difference Fourier synthesis and refined by the full-matrix least-squares to a final R factor of 0.040 based on 3261 unique reflections with intensities I≥3σ(I). The structure consists of two sots of tetraethylammonium cations and trinuclear Me cluster anions. In the cluster anion the three Mo atoms form an isosceles triangle with Mo-Mo distances of 2.601(1), 2.608(1), 2.642(1), respectively, showing a strong bonding interaction between the metal atoms. One μ_3-O atom and one μ_3-Cl atom are situated above and below the triangle respectively, binding the three Me atoms to form a triangular bipyramidal cluster core. Each pair of Mo atoms is bridged further by a μ_2-Cl atom situated on the Mo_3 triangular plane. In addition, each Me atom is coordinated to two terminal C1 atoms to complete a distorted octahedral coordination.

H+-gradient-dependent active transport of tetraethylammonium cation in apical-membrane vesicles isolated from kidney epithelial cell line LLC-PK1.

Transport of [3H]tetraethylammonium (NEt4+), an organic cation, has been studied by using apical-membrane vesicles isolated from cultured kidney epithelial cell line LLC-PK1. The uptake of NEt4+ by apical-membrane vesicles was osmotically sensitive, time-dependent and saturable. The presence of an H+ gradient ([H+]i greater than [H+]o) induced a marked stimulation of NEt4+ uptake against its concentration gradient (overshoot phenomenon), and this concentrative uptake was inhibited by HgCl2. These results suggest that apical membranes isolated from the LLC-PK1 cells retain the transport characteristics of NEt4+ similar to those observed in renal brush-border membranes.

RESEARCH ON TRINUCLEAR MOLYBDENUM CLUSTER COMPOUNDS——CRYSTAL AND MOLECULAR STRUCTURES OF (Et 4 N) 2 [Mo 3 (μ 3 -O)(μ 2 -Cl) 3 (Oac) 2 Cl 5

The title compound forms black crystals shaped like pseudo-octahedrons, which belong to the orthorhombic system The space group is Pna 2_1 with unit cell parametrs of a=17.815(1), b=16.629(2), c=12.003(1), and with Z=4, D_(obs)=1.80g·cm~(-3), and D_(calc)=1.804g·cm~(-3). The crystal structure was solved by the heavy atom method and refiened by fullmatrix least-squares to a final conventional R factor of 0.048 for 2584 unique reflections with I≥σ(Ⅰ). The investigation confirms that the crystal structure consists of tetraethylammonium cations and trinuclear Mo cluster anions. The anion is a μ_3-O monocapped trinuclear cluster with an average Mo-Mo bond length of 2.60 (2). On the side of the Mo_3 triangular plane opposite to the μ_3-O atom, each two Mo atoms are bridged by a Cl atom with the result that these seven atoms (3 Me, 1 O and 3 Cl atoms)form an apex-deficient quasicubane configuration. In addition, each Mo atom is coordinated to three additional atoms resulting in a pseudo-octahedral geometry around each metal center. These additional ligating atoms arise from two acetic radicals and five Cl atoms. The two O atoms of each acetic radical are attached to two ajacent Mo atoms respectively. As a whole, the cluster anion approaches the symmetry Cs.

Photodoping of polyacetylene films

A novel liquid phase (MeCN–Et4NClO4) photodoping of p-type polyacetylene film by tetraethylammonium cations in the potential range above –1.2 V vs. Ag/AgCl upon visible light illumination is reported.

Structure/activity studies of the nephrotoxic and mutagenic action of cysteine conjugates of chlgro and fluoroalkenes

The cysteine conjugates of the nephrotoxins hexachlorobutadiene (HCBD), tetrafluoroethylene (TFE) and hexafluoropropene (HFP), together with those of trichloroethylene and perchloroethylene, have been chemically synthesized and a relationship determined between their structures and their nephrotoxicity and mutagenicity in vitro. All of the conjugates had a marked effect on the uptake of both the organic anion p-aminohippuric acid (PAH) and the cation tetraethylammonium bromide (TEA) into rat kidney slices, suggesting activation of the conjugates in the slices to a toxic species which interferes with ion transport. This observation is consistent with the known nephrotoxicity of HCBD, TFE and HFP in vivo. Each of the conjugates was found to be metabolised by rat kidney slices and by semi-purified rat kidney beta-lyase to pyruvate, ammonia and an unidentified reactive metabolite. When semi-purified beta-lyase was used stoichiometric amounts of pyruvate and ammonia were produced. Although all of the conjugates were activated by beta-lyase and had a similar effect on ion transport their mutagenicity differed markedly. The conjugates of HCBD, trichloroethylene and perchloroethylene were mutagenic in the Ames bacterial mutation assay when activated by rat kidney S9. Metabolic cofactors were not required suggesting that activation was due to the enzyme beta-lyase. In the same assay the conjugates of TFE and HFP were not mutagenic either in the presence or absence of rat kidney S9 and cofactors. With a limited number of cysteine conjugates a clear distinction has been identified between the conjugates of chloroalkenes which were were similarly nephrotoxic but were not mutagenic. The mutagenicity of the cysteine conjugate of HCBD is consistent with the known renal carcinogenicity of this chemical.

A systematic electrochemical and spectroscopic study of mixed-ligand ruthenium(II) 2,2′-bipyridine complexes [Ru(bpy)3-nLn]2+ (n=0, 1, 2 and 3)

Cyclic voltammetry in water-free N,N -dimethylformamide (DMF) containing 0.1 M tetraethylammonium hexafluorophosphate (TEAH) at −54°C showed a complete set of six one-electron reversible reduction wave for each mixed-ligand ruthenium(II) 2,2′-bipyridine (bpy) complex [Ru(bpy) 3 - n L n ] 2+ (L=2-(2′-pyridyl)quinoline (pq), 2,2′-bipyrazine (bpz), 4,4′-diphenyl-2,2′-bipyridine (4-dbpy); n =0,1, 2, and 3), and extra waves for [Ru(bpy) 3- n (4-dbpy) n ] 2+ ( n =3, 2, and 1). It is demonstrated that the first three reduction waves are independent of an ion-association effect with tetraethylammonium cation, while their next three are affected. Cyclic voltammetric and spectroscopic data in acetonitrile and theoretical considerations lead to linear relations with unit slope between absorption (and emission) energy and the oxidation-reduction half-wave potential difference for these mixed-ligand Ru(II) bpy complexes. It is suggested that these relations can be an energy criterion for assignment of charge-transfer transitions (absorption and emission) for transition metal bpy complexes.

A systematic electrochemical and spectroscopic study of mixed-ligand ruthenium(II) 2,2′-bipyridine complexes [Ru(bpy) 3- nL n] 2+ ( n=0,1,2 and 3)

Cyclic voltammetry in water-free N,N-dimethylformamide (DMF) containing 0.1 M tetraethylammonium hexafluorophosphate (TEAH) at −54°C showed a complete set of six one-electron reversible reduction wave for each mixed-ligand ruthenium(II) 2,2′-bipyridine (bpy) complex [Ru(bpy) 3- nL n ] 2+ (L=2-(2′-pyridyl)quinoline (pq), 2,2′-bipyrazine (bpz), 4,4′-diphenyl-2,2′-bipyridine (4-dbpy); n=0,1, 2, and 3), and extra waves for [Ru(bpy) 3- n (4-dbpy) n ] 2+ ( n=3, 2, and 1). It is demonstrated that the first three reduction waves are independent of an ion-association effect with tetraethylammonium cation, while their next three are affected. Cyclic voltammetric and spectroscopic data in acetonitrile and theoretical considerations lead to linear relations with unit slope between absorption (and emission) energy and the oxidation-reduction half-wave potential difference for these mixed-ligand Ru(II) bpy complexes. It is suggested that these relations can be an energy criterion for assignment of charge-transfer transitions (absorption and emission) for transition metal bpy complexes.

The formation and structural chemistry of the hexa(μ- t-butylthiolato) pentacuprate(I) cage anion with triethylammonium and tetraethylammonium cations

Yellow (Et 4N)[Cu 5(SBu t ) 6] crystallises from solutions prepared from Cu(II), Bu t SH, Et 3N and Et 4NBr in acetone/ethanol, while (Et 3NH)[Cu 5(SBu t ) 6] crystallises from solutions of CuSBu t and Bu t SH in Et 3N. Crystal structure determinations reveal that both compounds contain the molecular cage [Cu 5(μ-SBu t ) 6] −, in which two copper atoms are three-coordinate (Cu trig), three copper atoms are two-coordinate (Cu dig), and all thiolate ligands are doubly-bridging. The polyhedral stereochemistry of the core is trigonal bipyramido-Cu 5- trigonal antiprismo-S 6. The complete [Cu 5(μ-SBu t ) 6] − cage in the Et 4N + compound closely approaches D 3 symmetry, but in the Et 3NH + compound one SBu t ligand is inverted at the sulphur bridge, causing angular distortions in the cage. Two structural features, the antiprismatic twist of the S 6 polyhedron and the bending of Cu dig towards the cage centroid (S-Cu dig-S = 171(1)°), provide evidence for weak Cu-Cu attractive interactions within the cage. Infrared data are discussed. Crystal data: (Et 4N)[Cu 5(SBu t ) 6], C 32H 74Cu 5NS 6, a = 45.500 (3), b = 11.805(1), c = 20.168(2) Å, β = 117.81 (1)°, C2/ c, Z = 8, R = 0.078 (2953 observed F); (Et 3NH)[Cu 5(SBu t ) 6], C 30H 70Cu 5NS 6, a = 10.519(1), b = 21.457(1), c = 20.065(1), β = 95.11(1), P2 1/ c, Z = 4, R = 0.072 (3093 observed F). (Et 4N)[Ag 5(SBu t ) 6] is isostructural with (Et 4N)[Cu 5(SBu t ) 6].

Regulation of a S(trans-1,2-dichlorovinyl)-L-cysteine-induced renal tubular toxicity by glutathione.

The nephrotoxin S-(1,2-dichlorovinyl)-L-cysteine (DCVC) is cleaved in the renal tubules to produce a reactive electrophilic intermediate. If this intermediate is responsible for the toxicity, addition of the nucleophilic scavenger glutathione (GSH) should decrease toxicity, and depletion of tubular GSH should enhance toxicity. GSH was added to isolated rabbit renal tubules simultaneously with, 15 min before, and 15 min after the addition of DCVC. The active accumulation of the organic anion para-aminohippuric acid (PAH) and organic cation tetraethylammonium bromide (TEA) was used as an index of renal toxicity. Incubation of renal tubules with 0.01-1 mM DCVC for 15 min decreased active transport, with complete inhibition at 1 mM. This was accompanied by a 50% decrease in non-protein sulfhydryl concentration. The addition of GSH (6 mM) simultaneously with DCVC completely prevented any decrease in active transport. The addition of GSH (6 mM) to tubules in which active transport was inhibited by DCVC reversed the inhibition to 80% of control. Similar enhancement of active transport occurred when tubules isolated 1 h after in vivo exposure to DCVC at 20-100 mg kg-1 were incubated with GSH (6 mM). Preincubation of renal tubules with GSH (5-15 mM) made them more refractory to the DCVC-induced decreased PAH and TEA transport. The inhibition of active transport by DCVC is enhanced if the tubular non-protein sulfhydryl is first lowered by diethyl maleate or glycidol. Thus, the tubular GSH concentration appears to be an integral component in regulating the alterations in active transport caused by DCVC.

Production of 18F-labeled compounds with 18F − produced with a 1-MW Research reactor

The feasibility of routine production of fluorine-18 labeled compounds for biomedical research with a 1 MW research reactor (10 13 n cm −2s −1) was examined. Studies were made of production of 18F by the 6Li(n, α) 3H, 16O ( 3H, n) 18F reactions, of the separation of 18F-fluoride from the 6LiOH·H 2O target material, and of the effects of other anions (introduced during work-up) on nucleophilic substitution reactions of fluoride. 1. (1) The practical half-saturation yield of 18F was limited to about 40 mCi because of local flux depression in the core of the reactor. 2. (2) Techniques of separation of no-carrier-added 18F from target material by ion-exchange chromatography are described in detail and compared with methods based on absorption on metal oxides and on distillation. All these methods yielded reactive, near-anhydrous acetonitrile solutions of the tetraethylammonium cation and 100–1000 μmol of anions other than fluoride. 3. (3) Methanesulfonate, nitrate and chloride were considerably, and hydroxide somewhat, less nucleophilic than fluoride. Sulfate, and especially acetate, inhibited nucleophilic substitution reactions of fluoride. 4. (4) Two-hour irradiations of 3 g of 6LiOH·H 2O gave net yields of up to 5–8 mCi of 18F compounds.

Electrolysis at the interface between two immiscible electrolyte solutions by means of a hanging electrolyte drop electrode

A three-electrode system with a hanging electrolyte drop electrode is described. The system facilitates analytical exploitation of electrolysis at the interface between two immiscible electrolyte solutions. Its use is demonstrated for the determination of micromolar concentrations of tetraethylammonium cation by differential pulse stripping voltammetry, based on transfer of the cation from water to nitrobenzene.

Nephrotoxicity following acute administration of N-(3,5-dichlorophenyl)succinimide in rats

The acute renal effects of the fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) were studied in male Sprague-Dawley rats. NDPS (50 mg/ kg, i.p.) increased urine volume and decreased food intake and body weight at 24 h but not 48 h. No change in urine content of the accumulation by renal cortical slices of the organic anion p-aminohippurate (PAH) or the organic cation tetraethylammonium (TEA) was observed with 50 mg/kg NDPS when compared to control animals. Rats receiving 100 or 200 mg/kg NDPS (i.p.) exhibited increased urine volume, proteinuria, glucosuria, decreased food intake and body weight, increased BUN and decreased accumulation of PAH and TEA at both 24 h and 48 h. These effects were generally more pronounced at the 200 mg/kg dose level. Pair-fed control experiments demonstrated that renal effects were NDPS-induced and not related to daily food consumption. No change in water intake was observed with any dose of NDPS used. The results demonstrate that NDPS alters renal function in a dose-dependent manner. In addition, NDPS (50 mg/kg) is capable of producing diuresis without apparent nephrotoxicity while doses of 100 mg/kg or more produce diuresis and nephrotoxicity.

Successive electron transfers to dibiphenylene-ethene molecule — effect of solvent and electrolyte

The polarographic and voltammetric behaviour of dibiphenylene-ethene (DBPE) has been studied in benzonitrile, acetonitrile, propylene carbonate, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, N,N-diethylformamide, pyridine, and ethylenediamine. The two successive reversible electron transfers have been observed in all these solvents. The separation between the formal potentials of DBPE/DBPE−• and DBPE−•/DBPE2− systems was found to vary with the properties of solvents and with the kind of supporting elecrtrolyte cations (tetraethylammonium and sodium perchlorates were used as electrolytes). The variation of redox potentials both with the solvent and the cation is discussed in terms of the donor–acceptor concept for solvent–solute interaction. Numerical analysis using both the values of the donor numbers and the acceptor numbers leads to successful description of experimental results. It has further been observed that DBPE2– dianion is protonized in ethylenediamine solutions.