Nataliya E. Borisova

New Diamides of 2,2′-dipyridyl-6,6′-dicarboxylic Acid for Actinide-Lanthanide Separation

The extraction of americium and lanthanides by diamides of 2,2′-dipyridyl-6,6′-dicarboxilic acid solutions in polar diluents was investigated. The dependence of extraction properties of the diamides on their structure was studied and the distribution ratios of americium and lanthanides from nitric acid solutions were determined. The highest extraction was found for the compounds with the ethyl-group and the alkyl-substituted aryl-group on the amidic nitrogen. The Am/Ln separation factors higher than 10 were achieved for extraction from high acidity media.

Novel diamides of 2,2′-dipyridyl-6,6′-dicarboxylic acid: synthesis, coordination properties, and possibilities of use in electrochemical sensors and liquid extraction

The procedure was proposed for the synthesis of various dipyridyldiamides. Their various properties in the series of rare-earth elements were studied. The possibility to use the synthe-sized compounds in polymer membranes of electrochemical sensors for the development of novel types of sensors was shown. A comparison of the influence of the ligand structure on the extraction and sensor characteristics was performed.

Pincer ligands based on α-amino acids: I. Synthesis of polydentate ligands from pyrrole-2,5-dicarbaldehyde

New chiral pincer ligands having CH=N moieties were synthesized by condensation of 1H-pyrrole-2,5-dicarbaldehyde with l-methionine and l-histidine methyl esters. Their reduction under mild conditions (NaBH4, −30°C) gave the corresponding amine ligands in high yields. An improved procedure for the preparation of 1H-pyrrole-2,5-dicarbaldehyde was proposed.

Bis(tetrabenzotriazaporphyrinato) and (tetrabenzotriazaporphyrinato)(phthalocyaninato) lutetium(III) complexes – novel sandwich-type tetrapyrrolic ligand based NIR absorbing electrochromes

The first sandwich-type complexes have been prepared for tetrabenzotriazaporphyrin ligands. The compounds reveal intrinsic UV-Vis/NIR absorption as well as peculiar electrochromic behavior. The heteroleptic (tetrabenzotriazaporphyrinato)(phthalocyaninato) lutetium derivative shows intermediate spectral and electrochemical properties with respect to homoleptic relatives.

Analysis of vibrational spectra of naphthalene, deuterionaphthalenes, and chromium (η6-naphthalene)tricarbonyl based on density functional calculations

The vibrational frequencies and force constants for naphthalene (C10H8), 1,4,5,8- and 2,3,6,7-tetradeuterionaphthalenes (C10H4D4), octadeuterionaphthalene (C10D8), and chromium (η6-naphthalene)tricarbonyl were calculated by the DFT method using the PBE approximation in extended and split bases. The results calculated without the use of scaling factors are in good agreement with the IR and Raman experimental data. All vibrational frequencies for the free ligand and π-complex molecules were assigned. The influence of coordination to the transition metal on the frequencies and force field of the naphthalene molecule (both for the free ring and the ring coordinated to the transition metal) was discussed.

Solvent switchable CuII complexes

A new tetranuclear complex Cu4, [Cu2L(OH)]2·2CH3OH·H2O (1), with the functionalized Schiff base ligand 2,6-bis((2-(acetylamino)phenylimino)methyl)-4-tert-butylphenol (H3L) has been obtained and characterized in the solid state by X-ray diffraction. The formation of the tetranuclear species is solvent dependent, the presence of water being a determinant in its isolation. Based on the mass-spectrometric evidence, the behaviour of the H3L–CuII system in the presence of water was investigated. Namely, water can switch the nuclearity of the CuII cluster from dinuclear to tetranuclear. The redox behaviour of this species in DMSO solution, showing two cathodic metal-centred peaks at EP = −0.80 and −1.35 V and an irreversible ligand-centred anodic peak at EP = 1.03 V, was found to be similar to that of a pristine dinuclear complex. The tetranuclear species was also characterized in the solid state by magnetic measurements, showing a dominating bulk antiferromagnetic behaviour, with a singlet ground state at approximately 2 K. DFT calculations permitted us to estimate the strong intradimer antiferromagnetic exchange interaction (J1 = −440 cm−1), together with two weak interdimer ferromagnetic exchange interactions (J2 = +0.5 and J3 = +1.7 cm−1).

Structure and vibrational spectra of dicyclopentadienylzinc. A DFT study

The quantum-chemical DFT calculations of the Cp2Zn structure confirm the conclusion made earlier from the vibrational spectra that the sandwich structure (η5-C5H5)2Zn (A) is not energetically favorable and more favorable are the close in energy πσ-structure (η5-C5H5)(η1-C5H5)Zn (B) and σ-structure (η1-C5H5)2Zn (C). The vibrational spectra of structures B and C with the DFT-derived force fields were calculated. A comparison of the calculated spectra of the isolated Cp2Zn molecules with the experimental data gives no way of deciding between the B and C structures. It is most likely that the molecule is nonrigid and experiences a strong influence from the nearest environment in solution or in the crystalline state.

Quantum chemical modeling of 2,2´-bipyridine-6,6´-dicarboxylic acid diamide structures: a relationship between the extraction ability and conformational behavior of the ligands

Approaches to the theoretical evaluation of a comparative affinity to metal ions of 2,2´-bipyridine-6,6´-dicarboxylic acid diamides, which are new promising extracting agents for the isolation of minor actinides from highly acidic radioactive waste, were tested in terms of the density functional theory (DFT) with the PBE0 functional in the TZ basis sets. The amides containing an aromatic substituent are more preorganized for binding with metal ion than their tetraalkyl-substituted analogs. However, the influence of substituents in the aromatic fragment of the molecule is very weak. The introduction of substituents into the pyridine or anilide fragment of the diamide molecule exerts almost no effect on the conformational dynamics and on the charges on the heteroatoms, whereas the extraction behavior depends strongly on these factors. The estimation of the affinity to metal ions by the calculation of the reorganization energy of the ligand for binding in a complex with metal gave the results differed from those calculated by the PBE0 method. The obtained values of the energies correlate well with the distribution coefficients of lanthanides for extraction from nitric acid solutions (Pearson´s coefficient is–0.86 for 0.5 M HNO3 and–0.91 for 1 M HNO3) and also are well described in the framework of the linear model. The method for the estimation of reorganization energies is more timeand labor-consuming than an analysis of the conformational behavior but gives much better results because makes it possible to evaluate qualitatively preorganization and find quantitative parameters for this estimation.

Binuclear and polynuclear transition metal complexes with macrocyclic ligands. 2. New macrocyclic Schiff"s base in the reaction of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene. Synthesis and structural, spectroscopic, and theoretical study

Condensation of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene in ethanol is accompanied by partial reduction of the azomethine double bonds to form symmetrical macrocyclic Schiffs base containing the alternating >C=N and >CH—NH fragments. In solution, this compound exists as the only isomer in which two endocyclic hydrogen atoms are bound to the oxygen atoms of the phenol groups and two other endocyclic H atoms are attached to the nitrogen atoms of the CH2—NH fragments. All endocyclic protons are involved in hydrogen bonding and undergo rapid exchange with each other at room temperature. In the crystal, the planar macrocyclic molecules are arranged in closely packed stacks. The steric hindrances resulting from overlapping of the bulky tert-butyl groups are eliminated through rotation of the molecules with respect to each other in the adjacent layers. Study of the potential energy surface for the Schiffs base under consideration by the DFT method demonstrated that the structure corresponding to the global minimum is similar to that found in solution. However, the isolated molecule is nonplanar, its macrocycle adopting a ladder conformation. The local minimum on the potential energy surface whose energy is 2.6 kcal mol–1 higher than that of the global minimum corresponds to the zwitterionic structure in which all four endocyclic hydrogen atoms are attached to the nitrogen atoms and the macrocycle adopts a tub conformation. Flattening of the ring is considered as a consequence of stacking interactions between the molecules in the crystal.

Crystal structure of bis-Isonicotinoyl hydrazone of 2,5-diformylpyrrole

Abstractbis-Isonicotinoyl hydrazone of 2,5-diformylpyrrole existing in the crystal in the form of a tetrahydrate of the hydrazone tautomeric form is synthesized and its structure is described. In the crystal, an infinite three-dimensional network of hydrogen bonds is formed by hydrazone molecules. The neighboring hydrazone molecules are bonded by intermolecular π stacking interactions. A quantum chemical calculation of the geometry and total energy of possible tautomers in vacuum and an aqueous solution is performed.