Multidentate Chelating Research Articles

1,10-Phenanthroline and Xenopus laevis Teratology

Frog oocytes and embryos have long served as traditional subjects of embryological research providing structural and functional information for the interpretation of the biological processes underlying development. A large number of various chemical agents induce typical teratological changes in frog embryos. However, the effects of metal deficiency of the first transition and IIB series or of chelating agents specific for these metals have never been examined in the frog. Multidentate chelating agents, including 1,10-phenanthroline (OP), which coordinate metals through N, O or S donor atoms are teratogenic also but in a manner characteristic for this class of reagents and completely different from those referred to above. Exposure to 10 −5 M OP causes maximal malformations with minimal mortality inducing craniofacial and skeletal abnormalities with failure of eye, head and other organ formation in 74% of frog embryos. In contrast, the non chelating analogue 1,7-phenanthroline (MP) has no effect at this concentration. A concentration of 10 −3 M OP is lethal. The known characteristics of either zinc and/or iron complexes with OP as well as the concentrations of these elements in frog oocytes and embryos are consistent with the hypothesis that the teratological observations are due to an effect of OP on either zinc or iron proteins.

Inhibition of catechol- O-methyltransferase (COMT) as well as tyrosine and tryptophan hydroxylase by the orally active iron chelator, 1,2-dimethyl-3-hydroxypyridin-4-one (L1, CP20), in rat brain in vivo

The orally active iron chelator, 1,2-dimethyl-3-hydroxypyridin-4-one (L1, CP20) proposed for reduction of iron overload in hemoglobinopathic patients, was studied in rats with respect to its ability to interfere with dopamine (DA) and serotonin (5-HT) metabolism. At 100 mg/kg i.p., it reduced the levels of DA, 5-HT, 5-hydroxyindoleacetic acid and particularly homovanillic acid in the rat striatum for several hours. These effects were shown to result from concomitant inhibition of catechol- O-methyltransferase (COMT; EC 2.1.1.6), tyrosine [tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating) (EC 1.14.16.2)] and tryptophan hydroxylase [tryptophan, tetrahydropteridine:oxygen oxidoreductase (5-hydroxylating) (EC 1.14.16.4)], with similar time-courses. COMT was inhibited with a threshold dose of about 1 mg/kg i.p. and an ed 50 of about 10 mg/kg i.p. as determined by the conversion of exogenous l-dihydroxyphenylalanine ( l-DOPA) to its O-methylated derivative. Tyrosine and tryptophan hydroxylase activities as measured by the accumulation of DOPA and 5-hydroxytryptophan, respectively, after central decarboxylase inhibition, were inhibited in striatum and cortex, with threshold doses of 3–10 mg/kg and ed 50s of about 20–30 mg/kg i.p. or p.o. While COMT inhibition by L1 is probably related to the structural similarity of the latter drug with the normal enzyme substrates, tyrosine and tryptophan hydroxylase inhibition is more likely due to coordination to iron bound to these enzymes. Desferrioxamine at 100 mg/kg i.p. did not show comparable effects. It is not known whether this relates to poor brain and/or cell penetration, or whether multidentate chelators are less suitable as inhibitors of aromatic amino acid hydroxylases

ChemInform Abstract: Laser Induced Vaporization Mass Spectrometry of a High Melting Multidentate Chelating Ligand and Its Ni(II) Bisdeprotonated Complex

Abstract The laser induced vaporization of 2,6-diacetylpyridine-bis(1-phthalazinylhydrazone) and of bis[2,6-di-acetylpyridine-bis-(1-phthalazinylhydrazonato) nickel(II)] allowed an easy description of the Electron Impact (EI) induced fragmentation pattern of the two compounds. The comparison with the spectra obtained with the usual heated probe is reported, showing that in that case the mass spectra collected are due to pyrolysis products.

Laser induced vaporization mass spectrometry of a high melting multidentate chelating ligand and its Ni(II) bisdeprotonated complex

The laser induced vaporization of 2,6-diacetylpyridine-bis(1-phthalazinylhydrazone) and of bis[2,6-di-acetylpyridine-bis-(1-phthalazinylhydrazonato) nickel(II)] allowed an easy description of the Electron Impact (EI) induced fragmentation pattern of the two compounds. The comparison with the spectra obtained with the usual heated probe is reported, showing that in that case the mass spectra collected are due to pyrolysis products.

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. IV. Metaxalone, 5-(3,5-Dimethylphenoxymethyl)-2-oxazolidinone; Evidence for Multidentate Chelation

Abstract The 60 MHz 1H NMR spectra of racemic metaxalone, 1, have been studied in CDC13 solution at 28° with the achiral shift reagent tris(6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato)europium(III), 2, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)-d-cam-phorato]europium(III), 3, and tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium(III), 4. Reagent 3 produced modest observable enantiomeric shift differences, ΔΔδ, for the CH20, aryl methyl, aryl H2,6 and the NH siqnals. Although reaquent 4 produced small or no observable ΔΔδ for the CH20, aryl methyls or aryl protons. strikingly qreater valuesof lanthanide induced shift, Δδ, as well as ΔΔδ, were found for the NH signal using 4 relative to 3. Analytical feasibility for direct optical purity determinations of 1 with 0 using this NH siqnal sclould allow detection of 74% of the minor enantiomer or less. Results are discussed ir terms of potential bidentate or tridentate chelation of 3 by 1 makinrl a greater contribution than for 4.

Structures of sodium zinc nitrilotriacetate monohydrate (173 K) and disodium hydrogen nitrilotriacetate (293 K)

NaZn(C6H6NO6).H20: Mr =29544, orthorhombic, P212121, a = 7.869 (4), b =9.783 (6), c = 12.292 (6) A,, V = 946-3 A, 3, Z = 4, Dx = 2.07 gcm -3, A (So Kc~) = 0.71073A,, /z=27.4cm -I Final R=0.052 for 859 unique reflections. The nitrilotriacetate ion is coordinated to the Zn 2+ ion in a tetradentate fashion. The remaining two octahedral sites about the Zn 2÷ ion are occupied by O atoms of different nitrilotriacetate ions. A comparison of the structure with other published structures identifies a common geometry, termed the 'butterfly' geometry, for transition-metal complexes with nitrilotriacetate ligands. The Na ÷ ions bridge the nitrilotriacetatozinc ions thereby holding the structure intact. The water molecule is coordinated to the five-coordinate Na ÷ ion. Na2(C6H7NO6): M, = 235-10, cubic, P213, a = 9-417 (2) ~, V = 835.1 A, 3, Z = 4, Dx = 1.87 g cm -3, A(Cu K6)= 1.54178 ~, p.=23.3 cm -l Final R = 0.034 for 208 unique reflections. The structure is the first observation of the zwitterionic form of the nitrilotriacetate ion as a tridentate chelating ion. The [C6H7NO6Na]- ions are linked together by a complex network of bridging Na ÷ ions. The differences in the coordination of the nitrilotriacetate ligand to the metal ions in these structures illustrate the versatile, multidentate chelating capabilities of the ligand.

Relative degradation rates of NTA, EDTA and DTPA and environmental implications

Multidentate chelating agents such as NTA, EDTA and DTPA are receiving widespread use in a variety of industrial applications and are entering natural water systems. The presence of these chelates in the environment can be undesirable because they solubilise toxic heavy metals. We have analysed the relative biodegradabilities of NTA, EDTA and DTPA in several different chemical environments. The objective was to determine whether any particular chelate is significantly more biodegradable than the others and therefore more desirable from an environmental point of view. Our results suggest that total degradation (including biological and non-biological) rates decrease in the order: DTPA > EDTA > NTA over the short term and NTA ∼ DTPA > EDTA over the long term. However, photolysis appeared to account for a significant proportion of DTPA degradation. Therefore, considering only biodegradation: NTA > EDTA ∼ DTPA. Degradation rates of all three chelates are not rapid enough, even under ideal laboratory conditions, to preclude concern about their release to the environment.

ChemInform Abstract: COMPLEXES OF OPEN‐CHAIN TETRADENTATE LIGANDS CONTAINING HEAVY DONOR ATOMS

AbstractÜbersicht über Ligandsynthesen‐ und Untersuchungen von Koordinationschelaten mit Tetraphosphinen, Diphosphin‐Diarsinen, ‐Dithioäthern, ‐Diiminen, Tetraarsinen, Diarsin‐Dithioäthern und Tetrathioäthern.

Chemistry of heterocyclic compounds. 20. Multidentate chelating agents. Pyridine macrocyclic ether synthesis

Chemistry of heterocyclic compounds. 20. Multidentate chelating agents. Pyridine macrocyclic ether synthesis

Stability constant of Pa(V)-EDTA complex

Many investigations of protactinium chemistry have been reported, but few information has been given on the complex of protactinium(V) with multidentate chelating agent. In the present paper, the stability constant of complex of protactinium(V) with ethylenediaminetetraacetic acid (EDTA) was determined by means of solvent extraction method.

A kinetic study of isotopic exchange reactions between lanthanide ions and lanthanide polyaminopolycarboxylic acid complex ions—I isotopic exchange reactions of Ce(III) with Ce(HEDTA), Ce(EDTA) −, Ce(DCTA) − and Ce(DTPA) 2−

The rates and mechanisms of the isotopic exchange reactions of Ce(III) ions with Ce(HEDTA); Ce(EDTA) −; Ce(DCTA) − and Ce(DTPA) 2− complex ions have been investigated. The rate equations and the experimentally determined rate constants at 20°C, μ = 0·1 and acetate buffer concentration of 10 −2 M are as follows: • Rate = k 1[H +][Ce(HEDTA)]; where k 1 = 23·1 × 10 4 l.mole −1 min −1 • Rate = k 2[H +][Ce(EDTA) −]; where k 2 = 9·4 × 10 4 l.mole −1min −1 • Rate = k 3[H +][Ce(DCTA) −] + k 4[Ce(DCTA) −] + k 5[C(III)][Ce(DCTA) −] where k 3 = 3·9 × 10 3 l.mole −1min −1; k 4 = 4·2 × 10 −3min −1 and k 5 = 5·6l.mole −1min −1 • Rate = k 6[Ce(DTPA) 2−][H +] 2 + k 7[Ce(III)][Ce(DTPA) 2−] where k 6 = 3·0 × 10 8 l. −2 mole −2 min −1 and k 7 = 1·6 l.mole −1min −1 The mechanisms of the exchange reactions of the multidentate chelates are discussed in terms of the lability of the carboxylic acid groups. The exchange reactions are catalysed by acetate ions and the effects of increased acetate concentration on the various terms of the rate equations have been examined. Activation energies have been determined.

Multidentate chelating agents derived from Quinoline-8-aldehyde. II. Stereochemistry of complexes of a tridentate and a sexadentate ligand

Complexes of the sexadentate chelating agent, 1,8-bis(8- quinolylmethyleneimino)-3,6-diazaoctane with iron(II), cobalt(III), and nickel(II) are described. The mode of coordination of this base is such that its complexes must be very closely related structurally to octahedral complexes of 1-amino-2-(8-quinolylmethyleneimino)ethane, and the similarities in the properties of corresponding complexes of both bases reflect this relationship. The resolution of the cobalt(III) complexes of both bases into their stable enantiomorphous forms is described.

Multidentate chelating agents from Quinoline-8-aldehyde. I. Tridentate and quadridentate Schiff bases from primary diamines

Complexes of 1,2-bis(8-quinolylmethyleneimino)ethane with cobalt(II), nickel(II), and copper(II) are described. The copper complexes are five-covalent and, it is suggested, trigonal bipyramidal. Reaction of the Schiff base with iron(II), cobalt(III), and, under certain conditions, nickel(II) leads to its partial hydrolysis, and complexes of the tridentate 1-amino-2-(8-quinolylmethyleneimino)ethane are obtained. The hydrolysis of the Schiff base in the presence of metal ions is discussed in terms of steric effects within the base and of the stereochemical demands of the metal ions. Complexes of 1,2-bis(8-quinolylmethyleneimino)benzene and its hydrolysis derivative 1-amino-2-(8-quinolylmethyleneimino)ethane are also described.