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At least 19 recordsLinked to original sources
PubMed2005

Structural systematics of the [Cu(chelate)3][Y]2 series. An interesting crystallographic structural insight involving vibronic coupling and the Jahn-Teller effect (JTE). The syntheses and low temperature crystal structures of tris(2,2'bipyridyl)copper(II) tetraphenylborate and tris(2,2'bipyridyl)zinc(II) tetraphenylborate.

The crystal structures of [Cu(bipy)(3)][BPh(4)](2), 1, and [Zn(bipy)(3)][BPh(4)](2), have been determined at low temperature. 1 and 2 are closely related, but are not isostructural. Both contain a two-dimensional supramolecular construct (SC) involving a sandwich structure. 1 has a six-coordinate CuN(6) chromophore with a regular elongated octahedral stereochemistry and rhombic in-plane bond lengths. The associated tetragonality value, T, of 1 is 0.8868. 2 involves a six-coordinate octahedral chromophore. Differences between 1 and 2 relate to the tendency of copper(II) complexes to undergo a Jahn-Teller (JT) distortion. The zinc(II) cation feels solely the host site strain, whereas the copper(II) cation also involves vibronic JT type coupling. The copper polyhedron geometry is characterized by both phenomena, with the vibronic interaction dominating. Scatter plot analysis involving the tris-chelate copper(II) series suggests that neither pure Q(theta) or Q(epsilon) components or the a(2u) mode operate in isolation over the entire series. All three operate in combination with varying quantifiable contributions, leading to distortion from the regular tetragonal octahedral stereochemistry.

Journal Article↗
PubMed1983

Inhibition of [3H]acetylcholine active transport by tetraphenylborate and other anions.

The effects of tetraphenylborate and other anions on the active uptake of [3H]acetylcholine by synaptic vesicles isolated from Torpedo californica electric organ were studied. Tetraphenylborate completely inhibits active uptake with a half-inhibitory concentration of 0.3 microM. Dipicrylaminate also half-inhibits at 0.3 microM, phenyldicarbaundecaborane at 14 microM, fluoride at 2 mM, thiocyanate at 3 mM, and azide at 16 mM. Tetraphenylborate had no effect on the vesicle ATPase activity or the transmembrane electric potential at low concentrations where it inhibits [3H]acetylcholine active transport. The mechanism for tetraphenylborate inhibition is uncertain, but it might be similar to that of its action as a mitochondrial uncoupler. Solubility products for the acetylcholine, choline, and potassium salts of the tetraphenylborate and dipicrylaminate anions also were measured. The inhibition results confirm the hypothesis of Marshall and Parsons [Br. J. Pharmacol. 54:333-338 (1975)] that tetraphenylborate acts on intact neuromuscular preparations to inhibit transmitter storage, and constitute new pharmacological evidence that evoked release of acetylcholine is mediated by synaptic vesicles.

Acetylcholine↗
PubMed1975

Potential energy barriers to ion transport within lipid bilayers. Studies with tetraphenylborate.

Tetraphenylborate-induced current transients were studied in lipid bilayers formed from bacterial phosphatidylethanolamine in decane. This ion movement was essentially confined to the membrane in terior during the current transients. Charge movement through the interior of the membrane during the current transients was studied as a function of the applied potential. The transferred charge approached an upper limit with increasing potential, which is interpreted to be the amount of charge due to tetraphenylborate ions absorbed into the boundary regions of the bilayer. A further analysis of the charge transfer as a function of potential indicates that the movement of tetraphenylborate ions is only influenced by a certain farction of the applied potential. For bacterial phosphatidylethanolamine bilayers the effective potential is 77 +/- 4% of the applied potential. The initial conductance and the time constant of the current transients were studied as a function of the applied potential using a Nernst-Planck electrodiffusion regime. It was found that an image-force potential energy barrier gave a good prediction of the observed behavior, provided that the effective potential was used in the calculations. We could not get a satisfactory prediction of the observed behavior with an Eyring rate theory model or a trapezoidal potential energy barrier.

Biological Transport↗
PubMed2000

Liquid secondary ion mass spectrometric investigation of ion-pair precipitates of some ethoxylates with barium tetraphenylborate

Liquid secondary ion mass spectrometry seems to be useful technique for the qualitative characterization of ion-pair precipitates of ethoxylates with barium tetraphenylborate. In the positive mode, barium complexes of ethoxylates were examined. In the negative mode, the ion signal of tetraphenylborate had 100% intensity relative to the matrix peaks. The low-resolution mass spectra were found to be suitable for checking the purity of ion-pair precipitates of ethoxylates with barium tetraphenylborate. On the basis of B/E mass spectra, the fragmentation routes of [M - H + Ba](+) ions are proposed. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed2000

C-H-pi interactions in 1-n-butyl-3-methylimidazolium tetraphenylborate molten salt: solid and solution structures

The crystal structure of 1-n-butyl-3-methylimidazolium tetraphenylborate molten salt (1) shows C-H-pi interactions between the hydrogens of the imidazolium cation and the phenyl rings of the tetraphenylborate anion. The imidazolium ring is surrounded by three tetraphenylborate anions that are connected with the same cation by C-H-pi (phenyl rings) interactions. The nearest inter-ion interaction is found between the N-CH-N proton of the cation and the B-phenyl centroid (2.349 A) with a nearly T-shaped geometry. The inter-ionic solution structure of 1 has been investigated by the detection of inter-ionic contacts in 1H NOESY NMR spectra between the protons of the cation and the anion. The 1H-NMR spectra of molten salt 1 is almost independent of its concentration in [D6]DMSO solution, the imidazolium proton chemical shifts are in the expected region and there are no observable NOE effects between the protons of the cation with those of the anion, indicating that 1 behaves in [D6]DMSO as a solvent-separated ion pair. In CDCl3 the 1H-NMR spectra of 1 are concentration dependent and all the imidazolium protons are shielded as compared with those observed in [D6]DMSO. Moreover, the 1H NOESY NMR spectra show all the peaks affected by the interaction between the protons of the imidazolium cation and those of the anion, indicating that in CDCl3 1 possesses a contact ion pair structure. The NCHN proton of the cation exhibits the greatest shielding (up to -4.5 ppm). an indication of the existence of C-H-pi interactions, even in solution. The calculated distance of this proton to the phenyl centroid is 2.3 A for a C-H -pi angle of 180 degrees. The apparent volumes for the cation and anion, calculated from the measured 13C-NMR relaxation times, increase from 38 and 140 A3 in [D6]DMSO to 360 and 600 A3 in CDCl3, respectively; this indicates the formation of floating aggregates of the type (1)(n) in CDCl3 via weak hydrogen bonds, with increasing concentration.

Journal Article↗
PubMed2005

Molecular tectonics. Selective exchange of cations in porous anionic hydrogen-bonded networks built from derivatives of tetraphenylborate.

Tetraphenylmethanes with multiple hydrogen-bonding sites are known to associate to form robust porous supramolecular networks. Analogous anionic networks can be built from the corresponding tetraphenylborates. Crystallization of the tetraphenylphosphonium salt of tetraphenylborate 2 produces an anionic network in which 74% of the volume is available for including cations and neutral guests. Other salts of anion 2 with diverse cations crystallize consistently to form the same network, whereas a neutral analogue of anion 2, tetraphenylmethane 1, produces an uncharged network that is far less open. Cations can be exchanged in single crystals of salts of tetraphenylborate 2 with retention of crystallinity and with selectivities similar to those observed in typical zeolites. Together, these observations provide new strategies for making ordered molecular materials by design, and they reveal that constructing such materials from charged subunits offers special advantages.

Journal Article↗
PubMed1997

Trypanocidal effect of Ir-(COD)-pentamidine tetraphenylborate on Trypanosoma brucei and T. b. gambiense rodent models and serum kinetics in sheep.

Pentamidine di-(iridium cyclo-octadiene)tetraphenylborate, called Ir-(COD)-pentamidine tetraphenylborate, was selected from a primary screening as a promising trypanocidal compound. The compound was evaluated against three isolates: Trypanosoma brucei brucei CMP, T.b. brucei GVR 35 and T.b. gambiense Feo. On the T.b. brucei GVR 35 murine CNS model, no mouse was cured when the treatment was commenced 21 days post-infection whatever the treatment regimen. Nevertheless, in vitro the compound killed the trypomastigote forms of T. b. gambiense Feo at 0.6 microM. In vivo, the compound cured all mice infected 1 hour previously with T. b. gambiense Feo after a 10 mg/kg (6.3 mumol/kg) treatment subcutaneously administered in a single dose. Moreover, the compound was active at 1 mg/kg (0.6 mumol/kg) in a single dose against the early stage of the T. b. brucei Antat 1-9 sheep model. Serum kinetics data showed that pentamidine di-(iridium cyclo-octadiene) tetraphenylborate was distributed within deep compartment according to a monocompartmental model. The maximum iridium serum concentration was 198 micrograms/l corresponding to 1 mumol/kg of iridium derivative and this value remained stable for 30-50 hours post-treatment. Iridium was completely eliminated from the serum 700 hours post-treatment. all data obtained from these models are in favour of an activity in the early stage of the disease but indicate that the compound could not cross the blood-brain barrier despite its lipophilicity. Although iterative treatments with the compound rapidly induced the selection of iridium derivative refractory populations, the compound could be studied on pentamidine refractory strains.

Animals↗
PubMed1995

FIA titrations of ephedrine in pharmaceutical formulations with a PVC tetraphenylborate tubular electrode.

A flow injection system for the titration of ephedrine in pharmaceutical products with potentiometric detection was developed. For this purpose a tetraphenylborate tubular electrode was constructed. The electrode was prepared without inner reference solution and with a PVC membrane based on tetrapentylammonium tetraphenylborate as ion exchanger and 2-nitrophenylphenyl ether as mediator solvent. Its operational characteristics were evaluated in a low dispersion manifold and compared with more conventionally shaped electrodes using the same sensor. In the pH range 2.5-11.5, the electrodes showed linear response between 3.8 x 10(-6) and 0.1 M with a slope of -56.4 mV/log[BPh4]. Ephedrine determinations in pharmaceutical products were carried out in a single channel manifold with a mixing chamber incorporated and using the tubular electrode as detector. Recovery rates of 98.6 +/- 2.5% were obtained in the analysis of tables, nasal drops and syrups with a sampling rate of about 60 h-1.

Electrodes↗
PubMed2001

Flame atomic absorption spectrometric determination of trace amounts of manganese in alloys and biological samples after preconcentration with the ion pair of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and ammonium tetraphenylborate on microcrystalline naphthalene or by column method.

Manganese is quantitatively retained on 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)-ammonium tetraphenylborate with microcrystalline naphthalene or by a column method in the pH range 7.5-10.5 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of the manganese complex and naphthalene was dissolved with 5 ml of dimethylformamide and the metal was determined by flame atomic absorption spectrometry. Manganese complex can alternatively be quantitatively adsorbed on ammonium tetraphenylborate-naphthalene adsorbent packed in a column and determined similarly. About 0.1 microgram of manganese can be concentrated in a column from 500 ml of aqueous sample, where its concentration is as low as 0.2 ppb. Eight replicate determinations of 1.0 ppm of manganese gave a mean absorbance of 0.224 with a relative standard deviation of 1.8%. The sensitivity for 1% absorption was 19 ppb. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of manganese in various standard samples.

Alloys↗
PubMed2004

Triethylammonium tetraphenylborate dichloromethane solvate.

The crystal structure of the title compound, C6H16N+.C24H20B-.CH2Cl2, displays an N-H...pi interaction between the triethylammonium cation and a phenyl ring of the tetraphenylborate anion. The distance between the ammonium H atom and the edge of this phenyl ring is 2.40 (3) A. The ammonium group and the aryl moiety are nearly perpendicular, forming an intramolecular dihedral angle of 90.4 degrees. A C-H...pi interaction between the disordered dichloromethane solvate molecule and a phenyl ring of the tetraphenylborate anion is also present.

Journal Article↗
PubMed2001

Comparison of binding of tetraphenylborate and tetraphenylphosphonium ions to cyclodextrins studied by capillary electrophoresis.

Binding constants for tetraphenylborate and tetraphenylphosphonium ions (Ph4B- and Ph4P+) to cyclodextrins (CDs) to give 1:1 host-guest complexes have been measured using capillary electrophoresis. Mobilities of the ions as a function of gamma-CD concentration give binding constants, K, of 1.08 x 10(5) M-1 for Ph4B- and 0.6 x 10(1) M-1 for Ph4P+. This dramatic difference of four orders of magnitude in binding constants is not seen with beta-CD (K = 7.7 x 10(1) M-1 for Ph4B- and 3.7 x 10(1) M-1 for Ph4P+) or dimethyl (DM)-beta-CD (K = 46 x 10(1) M-1 for Ph4B-1 and 7.7 x 10(1) M-1 for Ph4P+). The crystal and hydrodynamic radii of the ions, the latter calculated from their absolute mobilities, indicate that Ph4B- is smaller than the gamma-CD cavity, whereas Ph4P+ is approximately the gamma-CD cavity size. Results suggest that Ph4B- fits exactly into a gamma-CD cavity, with hydrophobic contacts involving several of the phenyl rings, whereas Ph4P+ is too large to enable these multiple contacts to be made. When only a single phenyl ring can fit into the CD cavity, binding strengths are in the order DM-beta-CD > beta-CD > gamma-CD and Ph4B- > Ph4P+. Measurement of electrophoretic mobilities of the complexes shows that their hydrodynamic radii are in the order gamma-CD < beta-CD approximately DM-beta-CD for Ph4B- and gamma-CD > beta-CD approximately DM-beta-CD for Ph4P+.

Cyclodextrins↗
PubMed1976

Gravimetric determination of chlorhexidine using tetraphenylborate ion.

A precise and accurate gravimetric procedure was developed for the determination of chlorhexidine diacetate, digluconate, or dihydrochloride. Sodium tetraphenylborate solution was the precipitant in an acidic medium (pH 1). Tablets containing both chlorhexidine diacetate and benzocaine also were assayed.

Biguanides↗
PubMed1982

Tetraphenylborate-sensitive electrode for measuring membrane potential.

The paper describes the construction of a new type of ion-selective electrode sensitive to tetraphenylborate (TPB-) and its electric characteristics. The electrode responds to increasing concentrations of the TPB- anion in accordance with the Nernst equation and can be used down to 0.1 microM concentration. The applicability of the electrode for measuring the membrane potential (positive inside) was proved in inside-out oriented membrane vesicles derived from Paracoccus denitrificans. The calculated values were 175 +/- 12 mV with NADH and 180 +/- 6 mV with succinate.

Electrodes↗
PubMed2002

Column preconcentration and FAAS determination of copper, iron, nickel and zinc using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol-tetraphenylborate-naphthalene adsorbent.

A solid co-precipitated material obtained from an ion-pair of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and tetraphenylborate (TPB), and microcrystals of naphthalene has been tried as an adsorbent for the column preconcentration of copper(I), iron(II), nickel(II) and Zn(II). The retention of the metal ions was found to be maximum and constant in the pH range 3.0-8.0 for Cu, 3.8-7.5 for Fe, 4.5-7.5 for Ni and 8.5-11.0 for Zn. The elements were determined by FAAS after dissolving the metal along with the adsorbent in an organic solvent (10 mL of DMF). The characteristic concentration for 1% absorption was found to be 0.0332, 0.0536, 0.0537 and 0.0142 (aqueous medium 0.0512, 0.0638, 0.1294 and 0.0216) microg mL(-1) for Cu, Fe, Ni and Zn, respectively. The calibration plot was linear in the range 1.5-20.0, 2.0-38.0, 2.5-25.0 and 0.5-15.0 micro g in the final 10 mL of DMF solution for Cu, Fe, Ni and Zn, respectively. Various parameters such as pH, volume of buffer, amount of adsorbent, flow rate, preconcentration factor and effect of diverse salts and cations were studied. The optimised conditions were utilized for the determination of Cu, Fe, Ni and Zn in various water, beverage and human hair samples.

Azo Compounds↗
PubMed2000

Determination of methylmercury in fish tissue by gas chromatography with microwave-induced plasma atomic emission spectrometry after derivatization with sodium tetraphenylborate.

The detection of methylmercury species (MeHg) in fish tissue was investigated. Samples were digested with KOH-methanol and acidified prior to extraction with methylene chloride. MeHg was back-extracted from the organic phase into water. An aliquot of this aqueous solution (buffered to pH 5) was subjected to derivatization with sodium tetraphenylborate (NaBPh4) and then extracted with toluene. The organic phase containing MePhHg was injected into a gas chromatograph (GC) which is on-line with a microwave-induced plasma atomic emission spectrometer (MIP-AED). The quantification limit was about 0.6 microg/g and 0.1 microg/g of MeHg (as Hg) for 0.08 g of freeze-dried fish powder and 0.5 g of fresh samples, respectively. Two certified reference materials, CRM 464 (tuna fish) from Community Bureau of Reference-BCR and DORM-2 (dogfish muscle) from National Research Council Canada-NRC were selected for checking the accuracy of the method. This methodology was applied to the determination of MeHg in some kinds of fish from the Carmo river with alluvial gold recovery activities ("garimpos") in Mariana, Minas Gerais, Brazil.

Animals↗
PubMed1988

The influence of tetraphenylborates (hydrophobic anions) on yeast cell electro-rotation.

The action of a series of tetraphenylborate ion (TPB) derivatives on yeast cells was studied by electro-rotation of the pre-treated cells. TPB derivatives in which all four phenyl groups were substituted with fluorine, chlorine or trifluoromethyl were much more toxic than the unsubstituted compound, the effect increasing dramatically with increasing size of substituents. These observations suggest that the toxicity of these hydrophobic ions is determined mainly by their size and possibly also by the chemical inductivity of their substituent groups. The order of the toxicities of these ions was in fair agreement with literature values for their translocation rates across artificial bilayers. Incubation times of 3 h were used as standard, longer incubations (up to 48 h) showed that the number of cells affected by low doses of TPB increased with the logarithm of time after the first hour of incubation. Although measurements of the percentage of cells showing co-field rotation showed that controls were not adversely affected by incubations as long as 9 h, rotation spectra showed that some cells suffer loss of internal conductivity during extended incubations. Decrease of the pH of the incubation medium, or inclusion of high concentrations of NaCl or KCl, potentiated the effects of these hydrophobic ions. The toxicity developed slowly, and the sensitivity of the assay was only very weakly dependent on the cell suspension density.

Boron Compounds↗
PubMed1989

Tetraphenylborate potentiates the respiratory inhibition by the dopaminergic neurotoxin MPP+ in both electron transport particles and intact mitochondria.

The cytotoxicity of 1-methyl-4-phenylpyridinium (MPP+) is believed to arise as a consequence of its time- and energy-dependent accumulation inside mitochondria, followed by inhibition of electron transport at Complex I of the respiratory chain. Consistent with our proposal that the accumulation of MPP+ represents a passive Nernstian transport into mitochondria in response to the transmembrane electrochemical potential gradient, tetraphenylborate (TPB-) was found to accelerate the onset of the respiratory inhibition by MPP+ on intact mitochondria. Moreover, the ultimate level of inhibition reached was unexpectedly also increased. The latter is now explained by our finding that TPB- elicits a 12-fold enhancement of MPP+ inhibition of respiration in electron transport particles. It is suggested that TPB- facilitates access of MPP+ to its intramembrane site of inhibitory action in Complex I.

1-Methyl-4-phenylpyridinium↗
PubMed1991

MPTP-induced ATP depletion and cell death in neuroblastoma X glioma hybrid NG 108-15 cells: protection by glucose and sensitization by tetraphenylborate.

The toxic effect of the Parkinsonism-producing neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) was investigated using a neuronal cell culture system, namely, neuroblastoma X glioma hybrid NG 108-15. The cells were able to metabolize MPTP into its active metabolite MPP+ (1-methyl-4-phenylpyridinium ion) and to convert its derivative, 2'-methyl MPTP, to the corresponding pyridinium ion. Degenerative changes were observed in NG 108-15 cells when they were examined with a phase-contrast microscope following exposure to MPTP, MPP+, or 2'-methyl MPTP. These compounds also caused an increased leakage of LDH from the treated cells. An enhanced release of [14C]adenine nucleotides was observed from treated cells which were prelabeled with [14C]adenine. The cell death as indicated by the leakage of LDH and the release of adenine nucleotides was markedly reduced in the presence of a high concentration (25 mM) of glucose in the medium. MPTP and MPP+ induced a drastic depletion in cell ATP content prior to cell death. The ATP depletion was also reduced by the presence of a high concentration of glucose. In contrast, tetraphenylborate, a lipophilic anion, highly potentiated the ATP depletion and the subsequent cell death induced by MPTP. Thus, ATP depletion could be a major factor in MPTP-induced neuronal cell death.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗