Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Perchlorates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed1996

A Nearly Linear Single Hydroxo Bridge. Synthesis, Structure, and Magnetic Susceptibility of (&mgr;-Hydroxo)bis((tetraphenylporphinato)manganese(III)) Perchlorate.

The synthesis, X-ray structure, and magnetic susceptibility characterization of a hydroxo-bridged complex, (&mgr;-hydroxo)bis((tetraphenylporphinato)manganese(III)) perchlorate, {[Mn-(TPP)](2)(OH)}ClO(4), are described. The complex is readily prepared by a controlled hydrolysis of monomeric diaquo(tetraphenylporphinato)manganese(III) perchlorate. Interestingly, the bridging hydroxo complex appears to be more stable than the putative &mgr;-oxo complex in halocarbon solvents. The X-ray structure determination shows a complex in which two five-coordinate manganese(III) ions are bridged by a single hydroxo ligand with an average Mn-O distance of 2.026(1) Å and a Mn-O(H)-Mn bridge angle of 160.4(8) degrees. The two porphyrin planes are nearly coplanar, and the two metal ions are separated by 3.993 Å. The average Mn-N(P) distance is 2.008(7) Å. The two manganese ions are displaced by 0.19 and 0.20 Å from their respective 24-atom mean planes. Both of the two porphyrin rings are moderately S(4) ruffled and have a near-staggered orientation (the N-Mn-Mn'-N' dihedral angle is 29.9 degrees ). The four inter-ring pairs of meso-phenyl groups of the binuclear cation are extremely crowded, with a nearly perpendicular orientation for each pair. The solid-state magnetic susceptibility was measured over the temperature range 2-300 K. The observed behavior is typical of an exchange-coupled binuclear complex. The data were fit to the total spin Hamiltonian (H(tot) = H(1) + H(2) - 2J&Svector;(1).&Svector;(2)) of a zero-field-split, high-spin d(4)-d(4) dimer in its actual crystallographic geometry, using numerical techniques. The hydroxide bridge supports a relatively strong antiferromagnetic coupling (2J = -74.0 cm(-1)) between two zero-field-split (D = -10.8 cm(-1)) manganese(III) ions. Crystal data: a = 16.807(7) Å, b = 17.061(6) Å, c = 17.191(5) Å, alpha = 85.64(3) degrees, beta = 79.75(3) degrees, gamma = 61.95(2) degrees, triclinic, space group P&onemacr;, V = 4281(3) Å(3), Z = 2, R(1) = 0.0707 for 14 802 observed data based on F(o) >/= 4.0sigma(F(o)), R(2w) = 0.2007 for 21 696 total unique data, least-squares refinement on F(2) using all data.

Journal Article↗
PubMed2002

Electrostatic modulation by ionic aggregates: charge transfer transitions in solutions of lithium perchlorate-diethyl ether.

The ionic environment within solutions of lithium perchlorate-diethyl ether (LPDE) was probed by utilizing the extraordinary spectral shifts these media impart on various nitroanilines at 25 degrees C. These compounds all have UV-visible spectra that are sensitive to the polarity of the medium and the nitroanilines investigated all exhibited varying degrees of solvatochromatic behavior in LPDE solutions. In all cases, the low-energy absorbance band exhibited a dependence upon LiClO(4) concentration throughout the entire solubility range investigated. For 4-nitroaniline and N,N-dimethyl-4-nitroaniline bathochromic shifts of 51.3 and 62.0 nm, respectively, were observed on going from pure ether to a 5.7 M LPDE solution, corresponding to a stabilization of 10.55 and 11.13 kcal mol(-1), respectively, for this transition. Thus, as the medium changes from diethyl ether to one containing ionic clusters of lithium perchlorate-diethyl ether, less energy is required to transfer the molecules from their ground states to their first excited states. For 2,6-dibromo- and 2,6-diiodo-4-nitroaniline smaller red shifts of 19.0 and 9.0 nm, respectively, were noted over the same concentration range of LPDE, resulting in stabilizations of 4.45 and 2.11 kcal mol(-1), respectively. Analysis of the observed molar transition energies indicates that for 4-nitroaniline and N,N-dimethyl-4-nitroaniline the stabilization of the zwitterionic excited states of such push-pull molecules is on the order of 2.0 kcal mol(-1) per mol of added salt. Furthermore, such stabilization is independent of the composition of the media. Thus these compounds can act as solvent polarity indicators for LPDE solutions throughout the entire solubility range of LiClO(4) in diethyl ether. As such, linear relationships are seen between the E(T) values of 4-nitroaniline and N,N-dimethyl-4-nitroaniline and the log of the second-order rate constants for the [4+2] cycloaddition reaction of 9,10-dimethylanthracene and acrylonitrile in LPDE. We also observe linear relationships between the E(T) values of 4-nitroaniline and N,N-dimethyl-4-nitroaniline and the keto-enol ratio of acetylacetone in LPDE.

Journal Article↗
PubMed2002

Modulation of tautomeric equilibria by ionic clusters. Acetylacetone in solutions of lithium perchlorate-diethyl ether.

Acetylacetone (2,4-pentanedione, 1) is a molecule whose tautomeric forms are in dynamic equilibrium. Concentrated salt solutions in nonaqueous solvents exert a remarkable influence on the keto-enol ratio of this beta-diketone. The keto content of 1 increases from 5% in pure diethyl ether to 84.5% in a 4.14 M lithium perchlorate-diethyl ether (LPDE) solution, a nearly 17-fold increase. The equilibrium expression, K = [keto]/[enol] = k(f)/k(r), exhibits a linear dependence on [LiClO(4)], with the formal order of participation of lithium ion in the equilibrium being 1.0. A kinetic analysis reveals that k(f) is independent of LPDE concentration, whereas k(r) displays an inverse dependence on salt concentration, indicating preferential coordination of the keto tautomer with Li(+). Although 1 exits as the enol in water only to the extent of 16%, the addition of lithium perchlorate further reduces this figure. In an aqueous 4.02 M LiClO(4) solution, acetylacetone enol accounts for only 4.6% of the total amount of 2,4-pentanedione present. It has also been found that acetylacetone itself is an excellent solvent for LiClO(4) as well as for NaClO(4) with solutions containing up to 7.5 M LiClO(4) attainable. The enol content of 1 decreases dramatically from 81% to 7.4% on going from the neat liquid to a solution of 6.39 M LiClO(4) in acetylacetone.

Journal Article↗
PubMed2006

Vibrational spectroscopy at high pressure of the permanganate anion trapped in potassium bromide and potassium perchlorate matrices.

The effect of high pressure on the resonance Raman spectra of the permanganate ion isolated in potassium bromide and potassium perchlorate matrices has been investigated at room temperature for pressures up to 50 kbar. The pressure dependences of the anharmonicity constants and harmonic frequencies have been determined from the overtones of the totally symmetric nu1(A1) mode of the permanganate ion. For both matrices, as the pressure increases, the anharmonicity constants decrease slightly, while the harmonic frequencies increase steadily. The effect of the potassium bromide phase transition from a face-centered to a body-centered structure was observed on the permanganate ion Raman spectrum at approximately 24 kbar. The perchlorate matrix does not exhibit any phase transition under the experimental conditions used in this study.

Journal Article↗
PubMed2004

Proton dynamics in the perchloric acid clathrate hydrate HClO4.5.5H2O.

In the perchloric acid clathrate hydrate HClO4.5.5H2O, the perchlorate anions are contained inside an aqueous host crystalline matrix, positively charged because of the presence of delocalized acidic protons. Our experimental results demonstrate that the microscopic mechanisms of proton conductivity in this system are effective on a time scale ranging from nanosecond to picosecond. In the present paper, we discuss more specifically on the relaxation processes occurring on a nanosecond time scale by combining high-resolution quasielastic neutron scattering and 1H pulse-field-gradient nuclear magnetic resonance experiments. The combination of these two techniques allows us to probe proton dynamics in both space and time domains. The existence of two types of proton dynamical processes has been identified. The slowest one is associated to long-range translational diffusion of protons between crystallographic oxygen sites and has been precisely characterized with a self-diffusion coefficient of 3.5 x 10(-8) cm2/s at 220 K and an activation energy of 29.2+/-1.4 kJ/mol. The fastest dynamical process is due to water molecules' reorientations occurring every 0.7 ns at 220 K with an activation energy of 17.4+/-1.5 kJ/mol. This powerful multitechnique approach provides important information required to understand the microscopic origin of proton transport in an ionic clathrate hydrate.

Journal Article↗
PubMed2003

A barium perchlorate complex with a lateral macrobicycle derived from 1,10-diaza-15-crown-5 containing a phenol Schiff base spacer.

In the crystal structure of (acetonitrile-kappaN)[13-methyl-39-oxido-1,17,25-triaza-9-azonia-28,31,36-trioxapentacyclo[23.8.5.1(11,15).0(3,8).0(18,23)]nonatriaconta-3,5,7,9,11,13,15(39),16,18,20,22-undecaene-kappa(7)N(1),N(17),N(25),O(28),O(31),O(36),O(39)](perchlorato-kappa(2)O,O')barium(II) perchlorate acetonitrile hemisolvate, [Ba(ClO(4))(C(2)H(3)N)(C(33)H(40)N(4)O(4))]ClO(4) x 0.5CH(3)CN, the barium(II) cation is asymmetrically situated in the macrobicyclic cavity and is bound to seven of the eight heteroatoms of the macrobicyclic ligand, to the N atom of an acetonitrile molecule and to two O atoms of one perchlorate group. The azonia N atom is not coordinated to the barium(II) cation and is involved in an intramolecular hydrogen-bonding interaction with the oxido O atom.

Journal Article↗
PubMed2003

A barium perchlorate complex with a lateral macrobicycle derived from 4,13-diaza-18-crown-6 containing a pyridine Schiff base spacer.

In the crystal structure of (perchlorato-kappa(2)O,O'))(28,31,36,39tetraoxa-1,9,17,25,42-pentaazapentacyclo[23.8.5.1(11,15).0(3,8).0(18,23)]nonatriaconta-3,5,7,9,11,13,15,16,18,20,22-undecaene-kappa(8)N(1),N(9), N(17),N(42),O(28),O(31),O(36),O(39))barium(II) perchlorate, [Ba(ClO(4))(C(33)H(41)N(5)O(4))](ClO(4)), the Ba(II) cation is situated in the macrobicyclic cavity, bound to only eight of the nine available donor atoms of the Schiff base macrobicyclic receptor. The pivotal N5 atom does not belong to the coordination sphere of the Ba(II) ion, in spite of its endo conformation with the lone pair directed towards the inside of the cavity. The Ba(II) ion completes its coordination core with two O atoms of one bidentate perchlorate group.

Journal Article↗
PubMed2004

mu-Oxo-bis{[(6-hydroxymethyl-2-pyridylmethyl)bis(2-pyridylmethyl)amine-kappa)N,N',N'',N''',O]iron(III)} tetrakis(perchlorate).

The novel mu-oxo-diiron complex [Fe2O(BPHPA)2](ClO4)4 [BPHPA is (6-hydroxymethyl-2-pyridylmethyl)bis(2-pyridylmethyl)amine, C19H20N4O], contains a binuclear centrosymmetric [Fe2O(BPHPA)2]4+ cation (the bridging O atom lies on an inversion centre) and four perchlorate anions. Each iron ion is coordinated by four N atoms [Fe-N = 2.117 (5)-2.196 (5) A] and one O atom [Fe-O = 2.052 (5) A] from a BPHPA ligand, and by one bridging oxo atom [Fe-O = 1.7896 (9) A], forming a distorted octahedron. There are hydrogen bonds between the hydroxy group and perchlorate O atoms [O-H...O = 2.654 (7) A].

Journal Article↗
PubMed2005

The perchlorate salt of the novel diprotonated dinucleating ligand 1,3-bis{[2-(2-pyridinio)ethyl][2-(2-pyridyl)ethyl]amino}benzene.

In the title salt, 1,3-bis{[2-(2-pyridinio)ethyl][2-(2-pyridyl)ethyl]amino}benzene diperchlorate dihydrate, C34H38N(6)2+.2ClO4-.2H2O, the cation contains two ethylpyridyl and two ethylpyridinium pendant pairs anchored to the two N atoms of 1,3-phenylenediamine. The pyridyl and pyridinium N atoms are flanked by a molecule of water through strong hydrogen-bonding interactions [N-H...O = 2.762 (6) and 2.758 (6) A, and O-H...N = 2.834 (6) and 2.839 (6) A]. The water molecules have weak hydrogen-bonding interactions with the perchlorate anions as well. One of the perchlorate anions is severely disordered.

Journal Article↗
PubMed2006

Bis[bis(methoxycarbimido)amine-kappa2N,N']bis(perchlorato-kappaO)copper(II) bis[bis(methoxycarbimido)amine-kappa2N,N']bis(methanol-kappaO)copper(II) bis(perchlorate) methanol disolvate.

The title compound, [Cu(ClO4)2(C4H9N3O2)2][Cu(C4H9N3O2)2(CH4O)2](ClO4)2.2CH3OH, comprises two independent Cu(II) species lying on different inversion sites. In the Cu complexes, a distorted octahedral geometry arises (from basic square-planar N4 coordination) from the weak coordination of two perchlorate ions (as Cu-O) in one species and two methanol molecules in the other (also as Cu-O). Interactions between the O atoms of the perchlorate anions or methanol groups and the imide or amine NH groups afford an extensive intermolecular hydrogen-bonding network.

Journal Article↗
PubMed1981

[The diagnosis of the Pendred syndrome in children by the perchlorate discharge test with 123I (author's transl)].

A modified method for the diagnosis of the Pendred Syndrome in children by the Perchlorate discharge test using 123I is described. The older child, who has the Pendred Syndrome and the obligatory hearing deficit, frequently has neither a goitre nor hypothyroidism, but other investigations (bone growth, scars and function tests) can also show changes. However a more certain diagnosis of this disorder in children is possible by the Perchlorate discharge test using 123I. The test using 131I is no longer justified in the face of more recent radiobiological knowledge.

Child↗
PubMed1992

[Determination of moxalactam, aztreonam and imipenem by the perchloric hydroxylamine method].

The reaction of perchloric hydroxylamine was adopted for determination of new beta-lactam antibiotics within monobactam, carbapenem and oxazepam groups. Complexes formed in colour reaction are stable over 2 hours in the case of aztreonam and imipenem, and over 1 hour for moxalactam, statistical analysis proved that both hydroxylamine-perchloric and spectrophotometric methods can be used alternatively.

Anti-Bacterial Agents↗
PubMed1989

Influence of trace metals on serum total sialic acids and perchloric acid--soluble proteins and sialic acids in mice.

Male Swiss mice were exposed to a single LD50 (75%; i.p.) of mercury, zinc, lead and manganese to determine their influence on serum sialic acid and protein levels after a refractory period of 48 h. They significantly elevated, in different proportions, the serum levels of total and perchloric acid (PCA)-soluble sialic acids (biological marker) and PCA-soluble proteins, thus indicating their toxicity.

Animals↗
PubMed1978

Kinetics and mechanism of oxidation of promazine and promethazine by ferric perchlorate.

The equilibrium constants, kinetics, and mechanism of promazine and promethazine oxidation by ferric perchlorate were investigated at different temperatures and acidities using a stopped-flow spectrophotometric technique. The overall reaction can be represented as follows: (formula: see text) where P+ represents the radical cation corresponding to the phenothiazine derivative. The equilibrium quotients were evaluated at 1.00 M HClO4, 25.0 degrees, and ionic strength 1.0 M. The kinetics of reaction follow the equation: -d[P] divided by dt = k1[Fe3+][P]-k-1[Fe2+][P+] The rate constants k1 and k-1 are independent of acidity and are related to the corresponding equilibrium quotients.

Chemical Phenomena↗
PubMed2006

Analysis of the changes in the 1H NMR spectral pattern of perchloric acid extracts of C6 cells with growth.

The aim of this work was to identify spectral markers of cell proliferation that could be of use in clinical MRS. Cultured C6 ATCC rat glioma cells were used as models for this purpose and metabolites were extracted with perchloric acid at three different growth curve stages: log, confluence and post-confluence. 1D and 2D in vitro(1)H NMR spectra were recorded at 9.4 T. Statistically significant changes in myo-inositol and glutamine concentrations between log phase and post-confluence were found when normalized to the creatine ratio. The myo-inositol/creatine ratio was 2.76 +/- 0.82 at log phase increasing to 7.43 +/- 1.34 at post-confluence, while the glutamine/creatine ratio decreased from 0.22 +/- 0.03 to 0.10 +/- 0.02. No significant differences were recorded for other metabolites investigated. The fact that both myo-inositol and glutamine are detectable by in vivo MRS at clinical fields makes their changes relevant as potential astrocytic tumour proliferation rate markers in clinical MRS.

Animals↗
PubMed1990

Differences in metabolite content between intact pancreases and their perchloric acid extracts. A 2D 1H/31P correlation NMR study.

Perchloric and hydrochloric acid extracts of intact pancreases from healthy rats and from rats with experimental acute pancreatitis were analysed using 2D 1H/31P correlation NMR spectroscopy. Major differences were found in the 2D maps between the extracts and the intact tissues. In the case of the intact diseased pancreas the prominent 31P signal at the phosphodiester region has been assigned in our previous work as lecithin/taurocholate complex. However, the signal found in the same chemical shift region in extracts of diseased pancreases as well as healthy ones, is identified here as the phosphodiester residue of oligoribonucleotides. In these extracts additional 31P signals were found and assigned as phosphomonoester and phosphodiester hydrolysis products of RNA. The amounts of these compounds, as a function of the acid concentrations were determined, and conditions for their minimization were defined.

Animals↗
PubMed1994

1H NMR spectroscopic characterization of perchloric acid extracts from breast carcinomas and non-involved breast tissue.

High-resolution 1H NMR spectra were obtained from perchloric acid extracts of breast tumor specimens and adjacent non-involved tissue. Two-dimensional shift-correlated and homonuclear J-resolved spectroscopy were used to identify coupled resonances in the spectra. Chemical shifts, multiplicities and spin-spin coupling constants of several non-resolved resonances in the one-dimensional spectra could be determined by the two-dimensional methods. Several differences in the metabolite content of the two types of extracts were established. The spectra of extracts from non-involved tissue were dominated by signals from glucose and other carbohydrates, while most of the tumors had very low or no detectable levels of glucose. High concentrations of lactate, taurine and succinate, an increase of the phosphocholine level, and a very low phosphocreatine level were characteristic findings in the 1H spectra of tumor extracts. The variation in the level of myo-inositol follows the variation in glucose for the two types of tissue. Scyllo-inositol was for the first time observed in the NMR spectra from breast tissue. Uridine 5'-diphospho-N-acetylglucosamine and uridine 5'-diphospho-N-acetylgalactosamine have been identified and there is an increased level of these two hexoses in the tumor tissue. These results provide insight into breast tumor metabolism, by simultaneously detecting a large number of metabolites and demonstrate the potential for using 1H NMR spectroscopy for studying different metabolic pathways in breast tumors. At the same time they provide useful information for interpretation of in vivo 1H NMR spectra of breast tumors.

Breast↗
PubMed1997

The effects of exogenous thyroxine (T4) or triiodothyronine (T3), in the presence and absence of potassium perchlorate, on the incidence of metamorphosis and on serum T4 and T3 concentrations in larval sea lampreys (Petromyzon marinus L.).

Larval sea lampreys (Petromyzon marinus) measuring 100-119 mm in length were exposed to thyroxine (T4; 10 mg liter-1) or 3,5,3'-triiodothyronine (T3; 1 mg liter-1) in the presence and absence of the goitrogen potassium perchlorate (KClO4; 0.01%), for 4-24 weeks. Every 4 weeks, treated and untreated (control) groups of sea lampreys were examined for external signs of metamorphosis and serum was assayed for T4 and T3 concentrations. Precocious metamorphosis was observed following 8, 12, and 24 weeks of KClO4 treatment; however, metamorphosis was not observed in any control, or T4-, T3-, T4+KClO4-, and T3+KClO4-treated larvae. In addition, serum T4 and T3 concentrations were 62 and 72% lower in KClO4-treated individuals than in control animals, respectively. Treatment with exogenous thyroid hormones (TH), in the presence or absence of KClO4, resulted in serum T4 concentrations which were significantly greater (1.2- to 58-fold) than those of the controls in all sampling periods except one, but serum T3 concentrations were not significantly elevated in more than 50% of the cases. TH+KClO4 treatments produced serum T3 concentrations which were significantly greater than those of KClO4-treated animals and never less than those of controls. These data indicate that larval sea lampreys have a tremendous capacity to take up and store exogenous T4 in their serum, but the uptake and/or serum storage of T3 appears to be stringently regulated. Also, the absence of both metamorphosis and a decline in serum TH concentrations in TH+KClO4-treated animals suggests that a decline in serum TH concentrations may be an essential factor contributing to the induction of metamorphosis by KClO4.

Animals↗