Effect of 3<Emphasis Type="Italic">d</Emphasis>-metal dopants on the electronic properties of hexagonal titanium dioxide nanotubes

The electronic structure of hexagonal TiO₂ nanotubes doped with 3d transition metals from Sc to Zn was calculated by the linearized augmented cylindrical wave method. The calculated densities of states demonstrate that the substitution of Sc, V, Co, Cu, or Fe atoms for a part of Ti atoms leads to the decrease in the band gap width of the material from 4 to 2 eV. Such nanotubes are promising materials for creation of electrodes for electrochemical photolysis of water.     

Synthesis and sorption properties of layered hydrous manganese dioxide saturated with <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-metal cations

Layered compounds based on hydrous manganese dioxide (hereafter, Mn-phases) saturated with s-metal (Ba²⁺), p-metal (Pb²⁺), and d-metal (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺) cations, analogues of manganese minerals of oceanic ferromanganese formations (vernadite, birnessite, buserite-I, and asbolan), were prepared at 4–6°C. All Mn-phases have poorly ordered structures. The sorption properties of phase compounds were studied in relation to alkali-metal (Na⁺ and K⁺) and other s-, p-, and d-metal cations. The exchange capacities of Mn-phases for alkali cations are very low, within 0.02–0.10 mg-equiv/g; for the other cations, the exchange capacities are 0.13–4.20 mg-equiv/g. The sorption of divalent metal cations depends on the phase and chemical composition of the Mn-phase.     

5<Emphasis Type="Italic">p</Emphasis>-4<Emphasis Type="Italic">d</Emphasis> Emission spectrum with a cascade decay of the 3<Emphasis Type="Italic">d</Emphasis> vacancy in the Xe atom

The 5p-4d emission spectrum, obtained during cascade de-excitation of the initial deep 3d vacancy in the Xe atom, was calculated by directly constructing a decay tree in a stepwise manner. The cascade decay tree was constructed with allowance for all radiative and nonradiative channels of decay for the initial and all intermediate ionic configurations of the cascade. The probabilities of branching and transition energies were calculated in a one-electron approximation with averaging over configurations. The 5p-4d cascade emission spectrum has a complex structure with many components, which reflects the transitions from the wide variety of the many-hole intermediate configurations generated by the cascade. The calculated data agree well with the experiment.     

A DFT study of H<Subscript>2</Subscript>CO and HCN adsorptions on 3<Emphasis Type="Italic">d</Emphasis>, 4<Emphasis Type="Italic">d</Emphasis>, and 5<Emphasis Type="Italic">d</Emphasis> transition metal-doped graphene nanosheets

The binding of 3d (Sc, Ti, V), 4d (Y, Zr, Nb), and 5d (La, Hf, Ta) transition metals on graphene nanosheet (TM–GNS) with hydrogen-terminated edges and the adsorption of H₂CO and HCN molecules on the pristine and TM-doped GNSs were theoretically studied using a density functional theory method. The calculation showed that all TM atoms had strong binding with GNS, in which the Ta atom displayed the strongest interaction with GNS. The H₂CO and HCN molecules showed much stronger adsorption on the TM–GNSs than that on the pristine GNS. The H₂CO showed stronger interactions with TM–GNSs than that of HCN, in which the Ta-doping displayed the strongest interactions between the GNS and H₂CO or HCN. The adsorption interactions induced dramatic changes of TM–GNS electronic properties. The results revealed that the adsorption strength and sensor ability of GNS can be greatly improved by introducing appropriate TM dopants. Therefore, TM-doped GNSs are suitable for application in H₂CO and HCN storage and sensor.     

Electronic Properties of 3<Emphasis Type="Italic">d</Emphasis>-Metal-Doped Zirconia Nanotubes

The electronic structure of hexagonal ZrO₂ nanotubes doped by 3d-metal atoms was calculated by the linearized augmented cylindrical wave (LACW) method. The calculated densities of electronic states indicate that partial substitutions of zirconium atoms by transition metals (Sc, Ti, Mn, Co, and Zn) decrease the optical gap of (4,4) ZrO₂ nanotubes from 3.7 to 2–2.3 eV. Doping of nanotubes shifts optical absorption from the UV to the visible, and the nanotubes themselves become candidate materials for design of electrodes for electrochemical water photolysis.     

Synthesis,crystal structure,and magnetic properties of a 3<Emphasis Type="Italic">d</Emphasis>-3<Emphasis Type="Italic">d</Emphasis> mixed heterometallic coordination polymer

A 3d-3d heterometallic coordination polymer, M(Bpp)(BDC) (I) (M = Co and Zn, Bpp = 1,3-bis(4-pyridyl)propane and H₂BDC = 1,4-benzenedicarboxylic acid), has been prepared by hydrothermal synthesis and structurally characterized by IR, elemental analysis, and single-crystal X-ray diffraction. The Co(II) and Zn(II) ions in I are located indisorder with a molar ratio of 0.35: 0.65. Complex I crystallizes in the orthorhombic space group Pbca and displays a two-dimensional 2-fold interpenetrated structure with (4,4) topology. The coexistence of two metal ions in the structure makes them more thermally stable than thepreviously reported homometallic polymers of Co(II) or Zn(II) ions. Complex I exhibits weaker antiferromagnetism than the pure Co(II) complex owing to the incorporation of Zn(II).     

Splitting of the <Emphasis Type="Italic">d</Emphasis><Superscript><Emphasis Type="Italic">N</Emphasis></Superscript> atomic states in icosahedral 3<Emphasis Type="Italic">d</Emphasis> metal endofullerenes M@C<Subscript>60</Subscript>

Group-theoretical and quantum-chemical investigations of the spectrum of low-lying excited states have been performed by the ROHF and FCI-RAS (Full CI in Restricted Active Space) methods for 3d metal endofullerenes (MEFs) M@C₆₀ (M =Mn, Cr, and Fe) in different charged states. The major purpose of this study is quantum-chemical verification of the anomalous (“non-Bethe’s”) character of splitting of the d ^N atomic states in an electrostatic field with icosahedral symmetry, predicted previously within the theory of integral invariants theory. The interrelation between the integral invariants theory and the quantumchemical methods applied in this work is considered in detail. Our calculations suggest that the d ^N atomic states in the icosahedral field generated by fullerene C60 (I _h ) on a metal atom (ion) remain non-split for different charged states of the metal and C₆₀. Reasons for this phenomenon and other possible approaches to verification of the prediction are discussed. It is demonstrated that the d ^N states of the encapsulated metal are split in icosahedral 3d MEFs only under very strong compression of these structures.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Stability of <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-element diphosphates in water

The mean atomic Gibbs energies of formation of (Δ _f ? _at ⁰ ) of s-, p-, and d-element diphosphates have been calculated using ion increments of the Gibbs energy (Δ _f G ⁰). The diphosphate hydrolysis kinetics is considered, and a correlation between the Δ _f ? _at ⁰ values and the hydrolysis rate constants is presented.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

Electrospray mass spectra of aqueous solutions of 4<Emphasis Type="Italic">f</Emphasis>-3<Emphasis Type="Italic">d</Emphasis> heterometallic chelates

The composition of aqueous solutions of the heterometallic chelates MLnDTPA and Ln₂M₃(EDTA)₃ (H₅DTPA = diethylenetriaminepentaacetic acid; H₄EDTA = ethylenediaminetetraacetic acid; Ln = Eu, La; M = Ni, Mn) and the monometallic chelates H₃Ni(DTPA), HNi₂(DTPA), H₂La(DTPA), and H₂Eu(DTPA) was studied by electrospray mass spectrometry (ESIMS). The mass spectra indicate that there is equilibrium between chelated rare-earth and 3d-metal ions in the aqueous solution of the heterometallic chelates. Both monometallic and bimetallic diethylenetriaminepentaacetates are observed for the 3d elements. The intensity ratio of the chelated rare-earth and 3d-metal ions in the aqueous solutions of the heterometallic complexes is in agreement with the ratio of the stability constants of the respective monometallic chelates.     

Synthesis of 3<Emphasis Type="Italic">d</Emphasis>-3<Emphasis Type="Italic">d</Emphasis> heterometallic 4-amino-1,2,4-triazole complex with the structure depending on the reaction time

One-pot reaction containing Zn(NO₃)₂, Cd(NO₃)₂, NH₄SCN, and 4-amino-1,2,4-triazole (Atrz) was proceeded by refluxing for different periods and gave different products. When the mixture was refluxed for 1 h, the product was a 1D chain polymer [Cd(Atrz)₂(SCN)₂] _n . However, when the refluxing time was increased to 3 h, a novel 3D 3d-3d heterometallic framework complex [Cd_2.84Zn_2.16(Atrz)₆(SCN)₁₀] · 4H₂O (I) with 66 topology was obtained. The photoluminescence property of I in the solid state was discussed..     

Development of transition state analogue inhibitors for <Emphasis Type="Italic">N</Emphasis>-acetylglycosyltransferases bearing <Emphasis Type="SmallCaps">d</Emphasis>psico- or <Emphasis Type="SmallCaps">d</Emphasis>tagatofuranose scaffolds

New potential transition state analogue inhibitors for N-acetylglucosyltransferases (GnTs) were synthesised. These compounds based on psico- and tagatofuranose (structure) scaffold contained a 2-thiophenyl-1-O-diethylphosphate moiety mimicking the proposed model of the transition state of the enzymatic reaction catalysed by N-acetylglucosyltransferases. The synthesised compounds as well as their precursors were fully characterised by NMR, optical rotation and mass techniques. Anomeric configuration of tagatofuranose derivatives was confirmed by X-ray crystallography. Two types of potential human glycosyltransferase (GnTs) inhibitors representing donor UDP-GlcNAc, assigned for biological assays on human GnTs, were prepared.     

Bioconversion of <Emphasis Type="SmallCaps">d</Emphasis>-glucose into <Emphasis Type="SmallCaps">d</Emphasis>-glucosone by Glucose 2-oxidase from <Emphasis Type="Italic">Coriolus versicolor</Emphasis> at Moderate Pressures

Glucose 2-oxidase (pyranose oxidase, pyranose:oxygen-2-oxidoreductase, EC 1.1.3.10) from Coriolus versicolor catalyses the oxidation of d-glucose at carbon 2 in the presence of molecular O₂ producing d-glucosone (2-keto-glucose and d-arabino-2-hexosulose) and H₂O₂. It was used to convert d-glucose into d-glucosone at moderate pressures (i.e. up to 150 bar) with compressed air in a modified commercial batch reactor. Several parameters affecting biocatalysis at moderate pressures were investigated as follows: pressure, [enzyme], [glucose], pH, temperature, nature of fluid and the presence of catalase. Glucose 2-oxidase was purified by immobilized metal affinity chromatography on epoxy-activated Sepharose 6B-IDA-Cu(II) column at pH 6.0. The rate of bioconversion of d-glucose increased with the pressure since an increase in the pressure with compressed air resulted in higher rates of conversion. On the other hand, the presence of catalase increased the rate of reaction which strongly suggests that H₂O₂ acted as inhibitor for this reaction. The rate of bioconversion of d-glucose by glucose 2-oxidase in the presence of either nitrogen or supercritical CO₂ at 110 bar was very low compared with the use of compressed air at the same pressure. The optimum temperature (55°C) and pH (5.0) of d-glucose bioconversion as well as kinetic parameters for this enzyme were determined under moderate pressure. The activation energy (E _a) was 32.08 kJ mol⁻¹ and kinetic parameters (V _max, K _m, K _cat and K _cat/K _m) for this bioconversion were 8.8 U mg⁻¹ protein, 2.95 mM, 30.81 s⁻¹ and 10,444.06 s⁻¹ M⁻¹, respectively. The biomass of C. versicolor as well as the cell-free extract containing glucose 2-oxidase activity were also useful for bioconversion of d-glucose at moderate pressures. The enzyme was apparently stable at moderate pressures since such pressures did not affect significantly the enzyme activity.     

Synthesis of 3<Emphasis Type="Italic">d</Emphasis>-3<Emphasis Type="Italic">d</Emphasis> heterometallic 4-amino-1,2,4-triazole complex with the structure depending on the reaction time

One-pot reaction containing Zn(NO₃)₂, Cd(NO₃)₂, NH₄SCN, and 4-amino-1,2,4-triazole (Atrz) proceeded by refluxing for different periods and gave different products. When the mixture was refluxed for 1 h, the product was a 1D chain polymer [Cd(Atrz)₂(SCN)₂] _n . However, when the refluxing time was increased to 3 h, a novel 3D 3d-3d heterometallic framework complex [Cd_2.84Zn_2.16(Atrz)₆(SCN)₁₀] · 4H₂O (I) with 6⁶ topology was obtained. The fluorescent property of I in the solid state was discussed.     

Copolymer of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride with maleic acid as drug carrier

A copolymer of N,N-diallyl-N,N-dimethylammonium chloride with maleic acid of constant composition was prepared under the conditions of radical initiation. The possibility of the functionalization of the copolymer with drugs containing amino groups by polymer-analogous transformations was examined. Conditions were found for preparing conjugates of the copolymer with isoniazid. The structures and the quantitative compositions of the conjugates were determined by ¹³С NMR spectroscopy, and the possibility of preparing conjugates with controlled drug content was demonstrated.     

Mononuclear and heterodinuclear phenanthrolinedione complexes of <Emphasis Type="Italic">d</Emphasis>- and <Emphasis Type="Italic">f</Emphasis>-block elements

1,10-Phenanthroline-5,6-dione (Phd) complexes of group 3 and lanthanide elements having formulae Ln(hfac)₃(Phd) (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised and characterised. Complexes of d-block elements of the type [MCl(Phd)(p-cymene)]⁺ (M = Ru, Os) were also prepared. In all these species, coordination of the polydentate ligand occurs by the N-donor moieties, as indicated by DFT calculations. The novel compounds were tested, together with fac-ReBr(Phd)(CO)₃, as precursors for the preparation of heterobimetallic d/f derivatives. The reaction of the rhenium complex with yttrium or lanthanide anhydrous triflate salts led to the formation of the complexes ReBr(CO)₃(N,N′-Phd-O,O′)Ln(OTf)₃(THF) (Ln = Y, Eu, Yb), where the trivalent ions interacted with the quinonoid moiety. The redox properties of the rhenium centre were strongly affected by the coordination of Ln(OTf)₃, as observed by comparing the cyclic voltammetry measurements carried out on fac-ReBr(Phd)(CO)₃ and on ReBr(CO)₃(N,N′-Phd-O,O′)Y(OTf)₃.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

4<Emphasis Type="Italic">p</Emphasis><Superscript>2</Superscript> resonances in photoionization from 4<Emphasis Type="Italic">s</Emphasis>4<Emphasis Type="Italic">p</Emphasis> levels in neutral zinc

In neutral zinc the 4p ² configuration lies above the 3d ¹⁰4s ionization limit and its levels become perturbers in the continuum. Lines have been identified in the Zn I spectrum for the multiplet, whereas no lines have been found for transitions to 4p ^{2 1} D or ¹ S. In this paper, cross sections for photoionization from 4s4p levels are reported that reveal the positions and widths of the 4p ² resonances. Calculations were performed using the multiconfiguration Hartree-Fock (MCHF) and B-spline R-matrix (BSR) method. Results from Breit–Pauli calculations that ignore the background continua are also presented. Included in the latter are energies for the levels and transition data (transition energies, line strengths, f-values, and A-rates) for all E1 transitions between these levels. Transition energies and the agreement in the length and velocity values, particularly for allowed transitions, indicate the accuracy of the computational model. Line widths are compared with other estimates. Contribution to the Serafin Fraga Memorial Issue.     

Cycloaminomethylation of dihydric phenols catalyzed by <Emphasis Type="Italic">d</Emphasis>- and <Emphasis Type="Italic">f</Emphasis>-metal compounds

An efficient method has been developed for the synthesis of 7,16,25-triaryl-7,8,16,17,25,26-hexahydro-6H,15H,24H-tribenzo[f,m,t][1,5,8,12,15,19,3,10,17]hexaoxatriazacyclohenicosines, 3,8-diaryl-2,3,4,7,8,9-hexahydrobenzo[1,2-e:4,3-e′]bis[1,3]oxazines, 3,9-bis(chlorophenyl)-3,4,9,10-tetrahydro-2H,8H-benzo[1,2-e:3,4-e′]bis[1,3]oxazines, and 2,9-bis(chlorophenyl)-1,2,3,8,9,10-hexahydrobenzo[1,2-e:6,5-e′]bis-[1,3]oxazines via cycloaminomethylation of pyrocatechol, resorcinol, and hydroquinone with N,N-bis(methoxymethyl) anilines in the presence of samarium catalysts.