Phosphato Complexes Research Articles

New MCl3 (M = Y, Dy, Pr) Salicylato, Maleato, Phtalato, Phenylsufonato and Phosphato Complexes and Adducts: Synthesis and Infrared Study

New MCl3 (M = Y, Dy, Pr) Salicylato, Maleato, Phtalato, Phenylsufonato and Phosphato Complexes and Adducts: Synthesis and Infrared Study

Selective binding by a divanadium complex of arsenate over phosphate: A computational study

Density functional theory (M06-2X) calculations on divanadium complexes [(VO) 2(bpbp)(A)] 2+ of the oxo anions formate, phosphate, and arsenate (A = HCOO −, H 2 PO 4 - , H 2 AsO 4 - ) as well as the diaquo complex [(VO) 2(bpbp)(OH 2) 2] 3+ indicate increased binding in the series H 2O < HCOO − < H 2 PO 4 - < H 2 AsO 4 - . Aqueous solvation enhances the experimentally observed selective recognition of arsenate over phosphate indicating differences in hydration enthalpies of the respective complexes as the main reason for the surprising differentiation between dihydrogenphosphato and dihydrogenarsenato by the divanadyl complex [(VO) 2(bpbp)(OH 2) 2](ClO 4) 3·H 2O. Deprotonation of the dihydrogenphosphato/arsenato complexes to [(VO) 2(bpbp)(HXO 4)] + further increases preferential solvation of the arsenato over the phosphato complex.

Correction for Bose et al. , Non-DNA-binding platinum anticancer agents: Cytotoxic activities of platinum–phosphato complexes towards human ovarian cancer cells

Correction for Bose <i>et al.</i> , Non-DNA-binding platinum anticancer agents: Cytotoxic activities of platinum–phosphato complexes towards human ovarian cancer cells

Non-DNA-binding platinum anticancer agents: Cytotoxic activities of platinum–phosphato complexes towards human ovarian cancer cells

DNA is believed to be the molecular target for the cytotoxic activities of platinum (Pt) anticancer drugs. We report here a class of platinum(II)- and platinum(IV)-pyrophosphato complexes that exhibit cytotoxicity comparable with and, in some cases, better than cisplatin in ovarian cell lines (A2780, A2780/C30, and CHO), yet they do not show any evidence of covalent binding to DNA. Moreover, some of these compounds are quite effective in cisplatin- and carboplatin-resistant cell line A2780/C30. The lack of DNA binding was demonstrated by the absence of a detectable Pt signal by atomic absorption spectroscopy using isolated DNA from human ovarian cells treated with a platinum(II)-pyrophosphato complex, (trans-1,2-cyclohexanediamine)(dihydrogen pyrophosphato) platinum(II), (pyrodach-2) and from NMR experiments using a variety of nucleotides including single- and double-stranded DNA. Furthermore, pyrodach-2 exhibited reduced cellular accumulations compared with cisplatin in cisplatin- and carboplatin-resistant human ovarian cells, yet the IC(50) value for the pyrophosphato complex was much less than that of cisplatin. Moreover, unlike cisplatin, pyrodach-2 treated cells overexpressed fas and fas-related transcription factors and some proapoptotic genes such as Bak and Bax. Data presented in this report collectively indicate that pyrodach-2 follows different cytotoxic mechanisms than does cisplatin. Unlike cisplatin, pyrodach-2 does not undergo aquation during 1 week and is quite soluble and stable in aqueous solutions. Results presented in this article represent a clear paradigm shift not only in expanding the molecular targets for Pt anticancer drugs but also in strategic development for more effective anticancer drugs.

Synthesis and characterisation of the seven geometric isomers of [Co(dien)(ampy)Cl] 2+

All seven possible geometric [Co(dien)(ampy)Cl] 2+ isomers, four mer and three facial, have been synthesised using various methods (dien=diethylenetriamine, ampy=2-aminomethylpyridine). The least abundant and most reactive m2 isomer has been synthesised using a kinetic method—an azide competition experiment—while a novel method has also been devised for the m1 isomer, obtained through its phosphato complex. The solution structures have been determined using 2D NMR techniques (DQCOSY and NOESY). A simple NMR method for distinguishing anti and syn pairs is reported.

Polyoxometalate coordinated phosphato complexes: a possible model reaction for POM-nucleotide interaction

The dephosphorylation of ATP in the presence of unsaturated heteropoly anion [SiW 11O 39] 8− and transition metal ions, Mn II, Co II, Ni II and Zn II, generates phosphato derivatives, formulated as [SiW 11O 39M(P 2O 7)] 10−, (M= Mn II, Co II, Ni II and Zn II), which were also synthesized from pyrophosphate as a possible model reaction of polyoxometalate-nucleotide interaction.

(NH 3) 5CoOP(H)(O)OCo(NH 3) 5] 4+ and its conjugate acid; evidence for the P +O − description of a terminal PO bond

Bromine oxidation of the phosphite-bridged dimer [(NH 3) 5CoOP(H)(O)OCo(NH 3) 5] 4+ ( 1) in acidified aqueous solution (25°C, I=1.125 M, NaClO 4) gives the corresponding phosphato complex [(NH 3) 5CoOP(OH)(O)OCo(NH 3) 5] 4+. The reaction follows the rate law k obs= kK a[dimer] T/( K a+[H +])(1+ K Br 3 [Br −]), with K Br 3 (=[Br 3 −]/[Br 2][Br −])=17.6 M −1, and with K a (0.074±0.006 M) corresponding to the acidity constant of the acid conjugate [(NH 3) 5CoOP(H)(OH)OCo(NH 3) 5] 5+ ( 2), and k (1.00±0.05 M −1 s −1) to the rate constant for oxidation of 1. The reaction is interpreted as involving attack by free Br 2 on the O-atom of the terminal PO group in 1 and rate-determining PH bond breaking. The acidity constant of 2 was confirmed by independent spectrophotometric determination, K a=0.09±0.01 M, 25°C, I=1.0 M. Crystal structures are reported for both 1(ClO 4) 4·2H 2O and 2(ClO 4) 5·C 2H 5OH. The available evidence suggests that the terminal PO bond in 1 is best represented as a limiting case of the P δ+O δ− description.

Adsorption phenomena and magnetic properties of γ-Fe 2O 3 nanoparticles

The synthesis of powders of γ-Fe 2O 3 nanoparticles with different surface chemical states (hydration, sulphato and phosphato complexes), their characterization and zero-field-cooled magnetisation measurements are reported.

Solubility and phase behavior of Cr(III) oxides in alkaline media at elevated temperatures

A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of Cr2O3 and FeCr2O4 in alkaline sodium phosphate, sodium hydroxide, and ammonium hydroxide solutions between 21 and 288°C. Baseline Cr(III) ion solubilities were found to be on the order of 0.1 nmolal, which were enhanced by the formation of anionic hydroxo and phosphato complexes. At temperatures below 51°C, the activity of Cr(III) ions in aqueous solution is controlled by a Cr(OH)3·3H2O solid phase rather than Cr2O3; above 51°C the saturating solid phase is γ-CrOOH. Measured chromium solubilities were interpreted via a Cr(III) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from least-squares analyses of the data. The existence of four new Cr(III) ion complexes is reported: Cr(OH)3(H2PO4)−, Cr(OH)3(HPO4)2−, Cr(OH)3(PO4)3−, and Cr(OH)4(HPO4)-(H2PO4)4−. The last species is the dominant Cr(III) ion complex in concentrated, alkaline phosphate solutions at elevated temperatures.

The first tetranuclear vanadium(V) peroxo complex: Preparation, vibrational spectra and X-ray crystal structure of K 6[V 4O 4(O 2) 8(PO 4)]·9H 2O

The vanadium(V) peroxo phosphato complex K 7[V 4O 4(O 2) 8(PO 4)]·9H 2O has been obtained from the KVO 3KH 2PO 4KOHH 2O 2H 2OC 2H 5OH system. The X-ray structural analysis revealed a tetranuclear anionic structure in which two dinuclear [V 2O 2(O) 2) 2( μ- η 1 : η 2-O 2) 2] units are connected by the μ 4-PO 4 group.

Characterization of platinum(II)-phosphato complexes of uridine nucleotides

Reactions of uridine 5'-di- and -triphosphates with cis-diamminedichloroplatinum(II) at or near neutral pH yielded substantial phosphato chelates. Each nucleotide afforded a pair of diastereomers due to the creation of an asymmetric center at the α- and β-phosphorus atoms of the UDP and UTP upon complexation to platinum(II). In addition to the phosphato complexes, nitrogen (N(3)) bound complexes are also formed.

Purple acid phosphatase from bovine spleen. Interactions at the active site in relation to the reaction mechanism.

Oxidation of the reduced (pink) phosphate-free bovine spleen acid phosphatase with 1.5 mol H2O2 or sodium peroxodisulfate/mol, in the presence of Mes or Bistris pH 5, leads to a species with an absorption maximum at 558 nm. Addition of acetate or oxidation in the presence of acetate buffer engenders a species with a maximum at 550 nm. Addition of phosphate to both species shifts the maximum immediately to 540 nm; this is the species also found after preparation from the spleen. The assumption that these species represent strongly bidentate-binding hydroxo, acetato and phosphato complexes of the Fe(III)-Fe(III) system is supported by replacement reactions with other ligating oxoanions followed by their typical spectral shifts. These oxoanion complexes cannot be dissociated by gel filtration; this is possible only after reduction to the Fe(II)-Fe(III) system. The oxidized species without EPR signals below g values of 2 still reveals 5% activity which cannot be reduced to zero even in the presence of higher concentrations of peroxodisulfate. The pH optimum of the reaction with alpha-naphthyl phosphate shifts from 5.9 to 5.3 in the oxidized species. The apparent pK values around 4.5 as derived from the pH dependence of activity, of the EPR spectra, and the spectral shifts of the phosphate-saturated reduced and oxidized species are assigned to an aquo/hydroxo equilibrium at the Fe(III) or an equilibrium, where the phosphato ligand is replaced by a hydroxo ligand. A reaction mechanism is proposed in which a hydroxo ligand at the chromophoric Fe(III) attacks the phosphoric acid ester group only when that is monoprotonated and pre-oriented by electrostatic interaction with the nonchromophoric metal ion. Binding and inhibition studies with the oxoanions indicate that they compete with the catalytically active hydroxo group of the reduced and oxidized enzyme with nearly the same inhibition constants. Catalysis is not affected by the oxoanions which replace the additional mu-hydroxo ligand in the 558-nm-absorbing Fe(III)-Fe(III) species. In contrast to hemerythrin and ribonucleotide reductase, a binuclear iron center is proposed for the purple acid phosphatase, which is bridged by a carboxylato and two aquo/hydroxo groups, but without a mu-oxo bridge.

ChemInform Abstract: Phosphato Complexes of Platinum(II): 31P NMR and Kinetics of Formation and Isomerization Studies.

AbstractOrtho‐, pyro‐ and triphosphate anions form monodentate complexes with chloro(diethylenetriamine)platinum(II) chloride and various chelates with PtCl2(en) in the pH range 2‐11. Rate constants for these reactions are determined and the various phosphate complexes are characterized by 31P NMR spectroscopy.

Phosphato complexes of platinum(II): phosphorus-31 NMR and kinetics of formation and isomerization studies

Ortho-, pyro-, and triphosphate anions form monodentate phosphato complexes with chloro(diethylenetriamine)platinum(II) chloride and various chelates with dichloro(ethylenediamine)platinum(II) in the pH range 2-11. Monodentate complexations largely proceed through the direct reaction with the PtCl(dien){sup +}. Phosphorus-31 NMR spectra reveal coordination chemical shifts of 3-6 ppM for the phosphorus atoms of the bound phosphate groups. Only the monodentate ({gamma}-triphosphato)platinum(II) complex was detected by {sup 31}P NMR spectroscopy, although this ligand is capable of coordinating through the {beta}-phosphate group as well. Phosphorus-phosphorus coupling constants for Pt(dien)(H{sub 2}P{sub 2}O{sub 7}) and Pt(dien)(H{sub 2}P{sub 3}O{sub 10}){sup {minus}} complexes were found to be in the range 19-23 Hz. Chelation to dichloro(ethylenediamine)platinum(II) by pyro- and triphosphate ligands is accomplished primarily through aquations of the platinum substrate. The triphosphate ligand forms both {beta},{gamma}- and {alpha}{gamma}-linkage isomers; the six-membered chelate ring ({beta},{gamma}-complex) formation dominates at lower pH (3-4), whereas the formation of the eight-membered chelate ring is favored in the pH range > 6. Coordinated phosphate groups exhibit 4-12 ppM coordination chemical shifts, and phosphorus-phosphorus coupling constants of 19-22 Hz were observed for the triphosphato chelates. Linkage isomerizations, {beta}{gamma} {yields} {alpha},{gamma} and {alpha},{gamma} {yields} {beta},{gamma}, for triphosphato complexes mainly proceed through an intramolecular mechanism. 36 refs., 4 figs., 6more » tabs.« less

ChemInform Abstract: The Preparation of (Cotn2PO4) and (CotrpnPO4) and Kinetics of Phosphato Complex Formation from the Highly Reactive (Cotn2(OH)(H2O))2+ and (Cotrpn(OH)(H2O))2+ Cations.

AbstractThe phosphato cobalt(III) complexes (III) and (VI) are characterized by their electronic spectra.

Deactivation mechanism of excited uranium(VI) complexes in aqueous solutions

The rate of luminescence decay of various uranium(VI) complexes has been measured by a nitrogen laser photolysis method in aqueous solutions. It was found that the luminescence consisted of a short- and a long-lived component in aqueous solutions at pH > 3. These components were assigned as the emissions from excited aqua and hydrolysed ions, *UO2+2 and *(UO2)2(OH)2+2, for which the decay constants were defined as k1 and k2, respectively. k1 and k2 were unaffected by either the concentration of UVI ion or the pH. The quenching rate constant, kq, of various UVI complexes (fluoro, sulphato, phosphato complexes as well as aqua ones) was determined in aqueous solutions with various quenching anions, Cl–, Br–, I– and NCS–. The values of kq were well correlated with the redox potentials of quenching anions. The mechanism of the quenching reaction was interpreted on the basis of a linear free-energy relationship.

The preparation of [Cotn 2PO 4] and [CotrpnPO 4] and kinetics of phosphato complex formation from the highly reactive [Cotn 2(OH)(H 2O)] 2+ and [Cotrpn(OH)(H 2O)] 2+ cations

The complexes [Cotn 2PO4]·2H 20 and [CotrpnPO 4]·5H 2O have been prepared and characterized. The kinetics of the anation reactions of [Co(N 4)(OH)(H 20)] 2+ by phosphate was studied for the two systems (N 4)=tn 2 and trpn, at pH 6.5, 25 °C and μ=1.0 M. The results are consistent with S Nl IP mechanism involving rapid preequilibrium ion-pair formation, followed by a slow substitution step. The reactivity of [Co(N 4)(OH)H 20)] 2+ for phosphate complex formation decreases in the order trpn>tn 2>en 2.

Studies of the Formation of Complexes of Np(V) with Inorganic Ligands by Means of Solvent Extraction with 2-Thenoyltrifluoroacetone and 1,10-Phenanthroline. II. Fluoro, Sulfato, and Phosphato Complexes

Abstract The formation constants of the complexes of Np(V) with fluoride, sulfate, and phosphate have been determined in 1 mol dm−3 NaClO4 at 25 °C by means of the solvent-extraction method using 2-thenoyltrifluoroacetone and 1,10-phenanthroline. Extractions at various pH values revealed that H2PO4− and HPO42− participate in the complex formation of Np(V).

Magnetic susceptibility of uranium (IV) phosphato and phosphonato complexes

Three uranium(IV)-alkyl phosphato complexes U(O 2P(OR) 2) 4 (R = Me, Et, n Bu), four uranium(IV)-alkyl phosphonato complexes U(O 2PHOR) 4 (R = Me, Et, i Pr, n Bu) and a uranium(IV) bis(phenyl phosphonato) complex U(O 3PC 6H 5) 2 were prepared and their magnetic susceptibilities measured over the temperature range 4.2–300 K. All eight complexes showed normal paramagnetic behavior. Far infrared spectra were used to infer structures of the U(IV) coordination sphere of these polymeric solids. Magnetic susceptibilities calculated from crystal field theory agreed well with the experimental data.

Phosphato complexes of cobalt(III). IV. Hydrolysis in basic solution

The rates of hydrolysis of phosphato complexes of cobalt(111) in sodium hydroxide concentrations ranging from 0.02M to 0.37M, and at several ionic strengths, have been measured with a tracer technique. Bidentate phosphato complexes exhibit the same rates of hydrolysis as the corresponding monodentate complexes, due to a rapid conversion of the bidentate into the monodentate form. The general rate law for base hydrolysis of all the phosphato complexes is: d[PO34]/dt = {kH2O + kOH[OH-]}[complex] At 60� and at unit ionic strength, the rate constants for the complexes cis-[Co(NH3)4OH.PO4]-, cis-[Co en2OH.PO4]-, and [Co(NH3)5PO4] respectively are: 103kH2O (min-l) 85.0, 2.0, &lt;1; and 103kOH (1. mole-1 min-l) 42.7, 12.0, 69.5. Mechanistic conclusions have been based on the measured enthalpies and entropies of activation and deuterium solvent isotope effects. For all complexes, kH2O is identified with an aquation mechanism involving synchronous interchange of the phosphate and solvent water between the first and second coordination spheres of the complexes. In the case of the tetrammine and bis(ethylenediamine) complexes, kOH is identified with a process involving synchronous interchange of phosphate and hydroxide ion between the first and second coordination spheres of the complexes. In the case of the pentammine complex, an SN2CB mechanism is considered to be more probable. A comparison with the base hydrolysis of halogen complexes of cobalt(111) is presented.