Complexation of Cm(III) with 6-(5,6-dipentyl-1,2,4-triazin-3-yl)-2,2'-bipyridine studied by time resolved laser fluorescence spectroscopy

The complexation of Cm(III) with 6-(5,6-dipentyl-1,2,4-triazin-3-yl)-2,2'-bipyridine (C(5)-hemi-BTP) in a water-2-propanol solution is investigated by TRLFS. Upon increasing the concentration of C(5)-hemi-BTP in the Cm(III)-solution, three different species, the 1:1-, 1:2- and 1:3-complex, with emission bands at 599.9 nm, 607.3 nm, and 612.8 nm, respectively, are found. Hereby, slow complexation kinetics is observed which no other BTP-type ligand has shown up to now. The species distributions for various ligand concentrations are determined and stability constants are derived (log β(03) = 12.1 ± 0.1). As extraction with hemi-BTP ligands is only possible in the presence of a lipophilic anion, the complexation of Cm(III) with C(5)-hemi-BTP and 2-bromohexanoic acid is investigated to deduce the species formed in the extraction process. It is found that Cm(III) is coordinated by two C(5)-hemi-BTP ligands and one 2-bromohexanoate ligand. This species formed in aqueous solution is identical to the one from the extraction process.     

Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2':6',2'-terpyridine ligand: implications for actinide(III)/lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'?:?6',2'-terpyridine (CyMe(4)-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO(2)(2+)) ion were obtained by X-ray crystallographic analysis, and they showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. (1)H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligands.     

Development of normal phase-high performance liquid chromatography-atmospherical pressure chemical ionization-mass spectrometry method for the study of 6,6'-bis-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]-triazin-3-yl)-[2,2']-bipyridine hydrolytic degradation

In the field of nuclear waste management, the 6,6'-bis-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]-triazin-3-yl)-[2,2']-bipyridine (CyMe(4)BTBP) is a polycyclic N-based molecule eligible to remove actinides from spent nuclear fuel by liquid-liquid extraction processes. In such processes, the organic phase containing the extracting molecules will undergo hydrolysis and radiolysis, involving degradation products. The purpose of this work was to develop a normal phase chromatography (NP-HPLC) coupled to atmospherical pressure chemical ionisation-mass spectrometry (APCI-MS) method to separate and identify degradation products of CyMe(4)BTBP dissolved in octanol, submitted to HNO(3) hydrolysis. 1 mol L(-1) HNO(3) hydrolysis conditions were used regarding the selective actinides extraction (SANEX) process, while 3 mol L(-1) HNO(3) conditions were applied for the group actinide extraction (GANEX) process. The first step consisted in optimizing the chromatographic separation conditions using a diode array detection (DAD). Retention behavior of a non hydrolyzed mixture of N,N'-dimethyl-N,N'-dioctyl-hexyloxyethyl-malonamide (DMDOHEMA), a malonamide used in the SANEX process to increase the kinetic of extraction, and CyMe(4)BTBP were investigated on diol-, cyano-, and amino-bonded stationary phases using different mobile phase compositions. These latter were hexane with different polar modifiers, i.e. dioxane, isopropanol, ethanol and methylene chloride/methanol. The different retention processes in NP-HPLC were highlighted when using various stationary and mobile phases. The second step was the setting-up of the NP-HPLC-APCI-MS coupling and the use of the low-energy collision dissociation tandem mass spectrometry (CID-MS/MS) of the precursor protonated molecules that allowed the separation and the characterization of the main hydrolytic CyMe(4)BTBP degradation product under a 3 mol L(-1) HNO(3) concentration. Investigation of the CID-MS/MS fragmentation pattern was used to suggest the potential ways leading to this hydrolysis degradation product. This NP-HPLC-APCI-MS method development is described for the first time for the CyMe(4)BTBP and should provide separation methods regarding the analysis of polycyclic N-based extracting molecules and more generally for the investigation of the organic phase coming from liquid-liquid extraction processes used in nuclear fuel reprocessing.     

Cobalt(II) and copper(II) complexes of (2-thiophene)-(5,6-diphenyl-[1,2,4]-triazin-3-yl)hydrazone

New complexes having the formulae [L₂CoX₂] and [LCuCl₂], [LCuCl] and [LCu](ClO₄)₂ where L?=?(2-thiophene)-(5,6-diphenyl-[1,2,4]-triazin-3-yl)hydrazone TDPTH; X?=?Cl, OAc or ClO₄ have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moments and infrared, electronic and ESR spectral data. The IR spectra indicate that TDPTH is a neutral bidentate ligand, coordinating via a triazine-N and azomethine-N in [L₂CoX₂] and [LCuCl₂] with the thiophene-S not coordinated but is tridentate in [LCuCl] and [LCu](ClO₄)₂ through the same two nitrogen atoms and thiophene-S. The magnetic moment and electronic spectral data suggest a distorted octahedral structure for Co(II) complexes, a dimeric square pyramidal geometry for [LCuCl₂] through chloride bridges and a dimeric diamagnetic, four-coordinate copper in [LCu](ClO₄)₂ through thiophene-S bridges. The X-band ESR spectra of Co(II) complexes, in the solid state, are rhombic with three g values consistent with a high-spin distorted octahedral structure. The X-band ESR spectrum of the powdered sample of both [LCuCl₂]·2H₂O and [LCu](ClO₄)₂ at room temperature and at 77?K showed only one broad signal due to?ΔM _s?=?±?1 transition and a weak signal due to the forbidden?ΔM _s?=?±?2 transition, indicating an antiferromagnetic interaction between copper(II) centers whereas [LCuCl] is ESR silent, indicating a monovalent copper ion in this complex.     

Characterization and comparison of Cm(III) and Eu(III) complexed with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine using EXAFS, TRFLS, and quantum-chemical methods

The complexation of Cm(III) and Eu(III) with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (n-C3H7-BTP) in nonaqueous organic solution is studied with extended X-ray absorption spectroscopy. Bond lengths are the same in both complexes. Quantum-chemical calculations performed at different levels support this finding. On the other hand, the Cm.(n-C3H7-BTP)3 complex is formed at much lower ligand-to-metal concentration ratio than the Eu.(n-C3H7-BTP)3 complex, as shown by time-resolved laser-induced fluorescence spectroscopy. This is in good agreement with n-C3H7-BTP's high selectivity for trivalent actinides over lanthanides in liquid-liquid extraction.     

Toward a clear-cut vision on the origin of 2,6-di(1,2,4-triazin-3-yl)pyridine selectivity for trivalent actinides: insights from theory

Although BTP (2,6-di(1,2,4-triazin-3-yl)pyridine) has been widely evidenced as the most effective nitrogen ligand for the selective complexation of trivalent actinides from lanthanide counterparts, the origin of its selectivity is still an open question. Neither experimental data nor theoretical calculations have been able to rationalize the role of covalency in real experimental BTP complexes. We show herein with DFT calculations on [M(BTP)3]3+ (M = La, U, Cm, Gd) that, even if back-bonding effects are significant in the U-BTP bond, it is the contrast of donation on 6d and 5f Cm(III) orbitals that explains, at least in part, its selective complexation to BTP.     

Characterization of the electronic excited-state energetics and solution structure of lanthanide(III) complexes with the polypyridine ligand 6,6'-bis[bis(2-pyridylmethyl)aminomethyl]-2,2'-bipyridine

Absorption, emission, and excitation spectra for solid-state and solution of Tb(III), Dy(III), and Gd(III) complexes with the polypyridine ligand 6,6'-bis[bis(2-pyridylmethyl)-aminomethyl]-2,2'-bipyridine (C36H34N8) are presented. Measurements of excited-state lifetimes and quantum yields in various solvents at room temperature and 77 K are also reported and used to characterize the excited-state energetics of this system. Special attention is given to the characterization of metal-to-ligand energy transfer efficiency and mechanisms. The measurement of circularly polarized luminescence (CPL) from the solution of the Dy(III) complex following circularly polarized excitation confirms the chiral structure of the complexes under study. No CPL is present in the luminescence from the Eu(III) or Tb(III) complex because of efficient racemization. The variation of the magnitude of the CPL as a function of temperature from an aqueous solution of DyL is used for the first time to characterize the solution equilibria between different chiral species.     

Regioselectivity of cyclization of 1-(6-methyl-5-oxo-2,5-dihydro-1,2,4-triazin-3-yl)-4-arylthiosemicarbazides by treating with methyl iodide and dicyclohexylcarbodiimide

1-(6-Methyl-5-oxo-2,5-dihydro-1,2,4-triazin-3-yl)-4-arylthiosemicarbazides treated with methyl iodide in the presence of sodium acetate in ethanol convert into 6-methyl-3-arylamino[1,2,4]-triazolo[4,3-b][1,2,4]triazin-7(1H)-ones. In reaction with dicyclohexylcarbodiimide 6-methyl-3-arylamino[1,2,4]triazolo[3,4-c][1,2,4]triazin-5(1H)-ones were obtained which at heating in alcohol solution in the presence of sodium acetate or at 262–272°C underwent the Dimroth rearrangement to give 3-methyl-7-arylamino[1,2,4]triazolo[5,1-c][1,2,4]-triazin-4(8H)-ones.     

A new ytterbium(III) PVC membrane electrode based on 6-methy-4-{[1-(1H-pyrrol-2-yl)methylidene]amino}-3-thioxo-3,4dihydro-1,2,4-triazin-5(2H)-one

This study presents the development of an original electrode, employing 6-methy-4-{[1-(1H-pyrrol-2-yl)methylidene]amino}-3-thioxo-3,4dihydro-1,2,4-triazin-5(2H)-one (PMTO) as a suitable ionophore. Interestingly, the electrode performance provided a very good response for Yb³⁺ in a wide concentration range (from 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ mol L⁻¹) with a detection limit of 4.6 × 10⁻⁷ mol L⁻¹ and a slope of 19.5 ± 0.3 mV per decade of Yb³⁺ concentration. Furthermore, it possessed a fast response time of about 10 s and it functioned in the pH range of 3.3-8.0 with a usage of at least 2 months without observing any deviations. Noticeably, the proposed electrode revealed an excellent selectivity for Yb³⁺ over a broad variety of alkali, alkaline earth, transition and heavy metal ions. The practical applicability of the electrode was demonstrated by its utilization as an indicator electrode in the potentiometric titration of Yb³⁺ ions with EDTA and in the determination of F⁻ in mouth wash samples. Additionally, it was also applied for the determination of Yb³⁺ ions in binary mixtures.     

Thermal investigation of the crystallisation nucleant formed between 2,4,6 trinitrotoluene, (TNT) and 2,2′,4,4′,6,6′ hexanitrostilbene (HNS)

Hexanitrostilbene (HNS), is added to trinitrotoluene (TNT), in order to improve the grain structure of cast munitions. The formation and composition of the nucleant material has been investigated by thermal methods using mixtures of HNS and TNT, with composition in the range 0.5%, the normal casting level, to 50% w/w HNS to TNT. These were cycled between ambient and upper temperatures in the range 160 to 235°C. Endotherms in the DSC traces, due to nucleant decomposition, have been observed in situ without the need for separation and purification. DSC enthalpy measurements, before and after thermal decomposition, were used to determine the composition of separated nucleant. Nucleant regeneration after decomposition, was investigated by thermal methods. Nucleant could not be recrystallised from solvents. Results have been interpreted on the basis of the formation of a, solid solution of TNT in HNS, rather than a complex of formula TNT₂HNS.     

Study on the Synthesis of (Z)-2-(5-Amino-1,2,4-thiadizol-3-yl)-2-(methoxyimino)acetic Acid

Russian Journal of Organic Chemistry - (Z)-2-(5-Amino-1,2,4-thiadiazole-3-yl)-2-(methoxyimino)acetic acid, an important intermediate prod­uct in the synthesis of Ceftobiprole, was prepared...     

One-pot non-cyanide synthesis of 1-(pyridin-2-yl)isoquinoline-3-carbonitrile by reaction of 1-phenyl-2-[6-phenyl-3-(pyridin-2-yl)-1,2,4-triazin-5-yl]ethanone with 1,2-dehydrobenzene in the presence of isoamyl nitrite

Russian Journal of Organic Chemistry - The reaction of 1-phenyl-2-[6-phenyl-3-(pyridin-2-yl)-1,2,4-triazin-5-yl]ethanone with 1,2-dehydrobenzene generated in situ from anthranilic acid and excess...     

Structural relationships,crystal chemistry and anion substitution processes for M(III)X3 systems of the lanthanides and actinides

An examination of data for lanthanide and actinide phases with UCl₃-type and PuBr₃-type M(III)X₃ structures has shown that these systems are conveniently described by alternating layers of [MX₂]ⁿ⁺_n and [X]^n?_n. The relationships between the UCl₃- and PuBr₃-type structures are described and expanded to include a variety of anion substitution systems, M(III)X_3?xY_x. The two different types of [MX₂]ⁿ⁺_n layers observed in these systems are consistent with the existence of a novel structural unit, [M₂X₄]²⁺. The effects of radius ratio constraints and layering mechanisms on the phase equilibria and anionic substitution processes, polymorphism and crystal growth in the MX_3?xY_x systems are discussed.     

酰氨基硫脲及其相关杂环衍生物的研究III.1-(5-甲基异唑-3-甲酰基)-4-芳基氨基硫脲及其相关杂环衍生物

Eight 1-(5-methylisoxazol-3-ylcarbonyl)-4-substituted thiosemicarbazides (I), eight 3-(5-methylisoxazol-3-yl)-4-substituted-1,2,4-triazoline-5-thiones (II), seven 2-arylamino-5-(5-methylisoxazol-3-yl)-1,3,4-thiadiazoles, and five 2-arylamino-5-(5-methylisoxazol-3-yl)-1,3,4-oxadiazoles were prepared from isoxazole III and aryl isocyanates. The derivatives I and II showed antitubercular activity and promoted the growth of plumule of wheat in preliminary experiments     

Palladium complex of 6-(2-hydroxy-5-methylphenyl)-3-(pyridin-2-yl)-1,2,4-triazin-5(2<Emphasis Type="Italic">H</Emphasis>)-one: Synthesis,structure, and catalytic activity

Palladium(II) complex with 6-(2-hydroxy-5-methylphenyl)-3-(pyridin-2-yl)-1,2,4-triazin-5(2H)-one was synthesized for the first time. The ligand was prepared from 3-(pyridin-2-yl)-1,2,4-triazin-5(2H)-one and 4-methylphenol via nucleophilic substitution of hydrogen (S_N^H reaction). The complex was readily soluble in basic medium, and it effectively catalyzed Mizoroki-Heck reaction.