Hydro-ionothermal synthesis of lanthanide-organic frameworks with 1,4-phenylenebis(methylene)diphosphonate

A synthetic approach combining hydrothermal and ionothermal (eutectic mixture of choline chloride and malonic acid) procedures is proposed that allowed the isolation of the first lanthanide-organic frameworks with residues of 1,4-phenylenebis(methylene)- diphosphonic acid (H4pmd), [Ln(Hpmd)(H2O)] (where Ln3+ ) Ce3+ and Pr3+), exhibiting an unprecedented trinodal topology with 3- and 8-connected nodes. The structural details were unveiled from single-crystal X-ray diffraction and the materials were characterized using standard techniques.FCT - POCI-PPCDT/QUI/58377/2004FEDER - POCIGrant - SFRH/BPD/9309/200

eredeti népszinmü 3 felvonásban - irta Balogh - zenéjét Szerdahelyi

Debreczeni Szinház. Vasárnap, január 1-én 1871. adatik.Debreceni Egyetem Egyetemi és Nemzeti Könyvtá

(dme)MCl_3(NNPh_2) (dme= dimethoxyethane; M= Nb, Ta): A Versatile Synthon for [Ta═NNPh_2] Hydrazido(2-) Complexes

Complexes (dme)TaCl_3(NNPh_2) (1) and (dme)NbCl_3(NNPh_2) (2) (dme =1,2-dimethoxyethane) were synthesized from MCl5 and diphenylhydrazine via a Lewis-acid assisted dehydrohalogenation reaction. Monomeric 1 has been characterized by X-ray, IR, UV−vis, ^(1)H NMR, and ^(13)C NMR spectroscopy and contains a κ^(1)-bound hydrazido(2-) moiety. Unlike the corresponding imido derivatives, 1 is dark blue because of an LMCT that has been lowered in energy as a result of an N_(α)−N_(β) antibonding interaction that raises the highest occupied molecular orbital (HOMO). Reaction of 1 with a variety of neutral, mono- and dianionic ligands generates the corresponding ligated complexes retaining the κ^(1)-bound [Ta−NNPh_2] moiety

Amine, Amido, and Imido Complexes of Tantalum Supported by a Pyridine-Linked Bis(phenolate) Pincer Ligand: Ta−N π-Bonding Influences Pincer Ligand Geometry

A series of tantalum imido and amido complexes supported by a pyridine-linked bis(phenolate) ligand has been synthesized. Characterization of these complexes via X-ray crystallography reveals both C_s and C_2 binding modes of the bis(phenolate)pyridine ligand, with complexes containing two or fewer strong π-donor interactions from ancillary ligands giving C_s symmetry, whereas three strong π-donor interactions (e.g., three amido ligands or one amido ligand and one imido ligand) give C_2-symmetric binding of the bis(phenolate)pyridine ligand. DFT calculations and molecular orbital analyses of the complexes have revealed that the preference for C_s-symmetric ligand binding is a result of tantalum−phenolate π-bonding, whereas in cases where tantalum−phenolate π-bonding is overridden by stronger Ta−N π-bonding, C_2-symmetric ligand binding is preferred, likely because conformationally this is the lowest-energy arrangement. This electronically driven change in geometry indicates that, unlike analogous metallocene systems, the bis(phenolate)pyridine pincer ligand is not a strong enough π-donor to exert dominant control over the electronic and geometric properties of the complex

Light scattering by optically anisotropic scatterers II: T--matrix computations for radially and uniformly anisotropic droplets

This is the second paper in a series on light scattering from optically anisotropic scatterers embedded in an isotropic medium. The apparently complex T-matrix theory involving mixing of angular momentum components turns out to be an efficient approach to calculating scattering in these systems. We present preliminary results of numerical calculations of the scattering by spherical droplets in some simple cases. The droplets contain optically anisotropic material with local radial or uniform anisotropy. We concentrate on cases in which the scattering is due only to the local optical anisotropy within the scatterer. For radial anisotropy we find non-monotonic dependence of the scattering cross-section on the degree of anisotropy can occur in a regime for which both the Rayleigh and semi-classical theories are inapplicable. For uniform anisotropy the cross-section is strongly dependent on the angle between the incident light and the optical axis, and for larger droplets this dependence is non-monotonic.Comment: 14 pages, 6 figures, uses RevTex

The Composition of Arylstibonic Acids

This thesis describes a detailed ESI-MS investigation into the arylstibonic acids, organo-antimony-containing compounds that are currently of interest as anticancer reagents. Four arylstibonic acids, of nominal formula RC6H4SbO3H2 [R = p-chloro-, p-tolyl-, p-nitro- and α-naphthyl-] were synthesised, and a further eight archival samples from the National Cancer Institute Repository were obtained for use in the project. Results indicate clearly that the acids exist as polyoxometalate aggregates [H8(RSb)12O28], rather than monomeric species, in both the solid state and in acetonitrile solution, thus resolving a century-old debate concerning the nature of their molecular composition. Variations in solvent, time in solution and pH have also defined the stability of these aggregates under different conditions. Synthesis of arylstibonic acids by traditional methods (pre-1940) has been shown to lead to products contaminated with cations present during their preparation. An improved method of synthesis has been devised, and the crystal structure of an intermediate in the synthesis of these acids, [C6NH6][p-O2NC6H4SbCl5], is reported. Salts of arylstibonic acids with a range of cations were investigated by ESI-MS and shown to form a diverse family of polyoxostibonates with nuclearities including Sb12, Sb14 and Sb16. Crystal structures containing some of these aggregates, verified through parallel studies with collaborators, are described. Preliminary study of mixed polyoxometalates (Sb/As) showed a strong tendency to form As4Sb2 species but these could not be fully characterised

Модели адаптивной навигации в учебной гиперсреде

Предлагается модель навигации в учебной гиперсреде, обеспечивающая адаптацию сценариев обучения и контроля к имеющимся знаниям обучаемого и целям обучения. Адаптация осуществляется на основе построения дидактического образа знаний и учета логических зависимостей элементов учебной гиперсреды. Сценарий обучения содержит неизбыточную последовательность элементов гиперсреды, которые необходимо изучить. Сценарий контроля содержит наиболее сложные вопросы из тех, на которые обучаемый в состоянии ответить.Пропонується модель навігації у навчальному гіперсередовищі, яка забезпечує адаптацію сценаріїв навчання і контролю до наявних знань навчаного і цілей навчання. Адаптація здійснюється на основі побудови дидактичного образу знань і обліку логічних залежностей елементів навчального гіперсередовища. Сценарій навчання містить ненадмірну послідовність елементів гіперсередовища, які необхідно вивчити. Сценарій контролю містить найскладніші питання з тих, на які навчаний в змозі відповісти.The model of navigation in the e-learning hypermedia system is offered, providing the training and control script adaptation to the level of learner knowledge and his learning aims. Adaptation is realized by construction of the image of didactic knowledge and taking into account the logical dependences of hypermedia elements. The training script contains irredundant sequence of hypermedia elements, which are necessary to study. The control script contains the most difficult questions, which learner can answer t