Structural Inhomogeneity in Electrolyte Solutions: The Calcium Perchlorate–Water System

A new approach has been proposed to study the structure of aqueous electrolyte solutions. NIR, Raman and attenuated total reflectance, Fourier transform infra-red (ATR FTIR) spectra have been measured for aqueous calcium perchlorate solutions in the 0.22–4.3 mol·L^?1 (0.22–7.46 mol·kg^?1) concentration range at 25 °C. By the methods of principal component analysis (PCA) and multivariate curve resolution—alternating least squares (MCR-ALS) the number, spectra and concentration profiles have been determined for spectroscopically distinguishable forms of water and ClO ₄ ^? ion in solutions. The results have been analyzed using a phenomenological model, establishing thereby: concentration ranges for structural rearrangements of the solution, the nature of structural microirregularities and different states of the ClO ₄ ^? ion in the areas of domination of the natural water structure, and of cybotactic groups of calcium perchlorate hexa and tetra hydrates.     

Ionization penalty in nonlinear Raman neuroimaging

Light-assisted ionization accompanying coherent anti-Stokes Raman scattering (CARS) of ultrashort laser pulses in brain tissue is shown to manifest itself in a detectable blueshift of the anti-Stokes signal. This blueshift can serve as an indicator of ionization processes in CARS-based neuroimaging.     

Co-encapsulation of enzyme and sensitive dye as a tool for fabrication of microcapsule based sensor for urea measuring

Enzyme based micron sized sensing system with optical readout was fabricated by co-encapsulation of urease and dextran couple with pH sensitive dye SNARF-1 into polyelectrolyte multilayer capsules. Co-precipitation of calcium carbonate, urease and dextran followed up by multilayer film coating and Ca-extracting by EDTA resulted in the formation of 3.5-4 micron capsules, what enable the calibrated fluorescence response to urea in concentration range from 10(-6) to 10(-1) M. The presence of urea can be monitored on a single capsule level as illustrated by confocal fluorescent microscopy. Variations in urease:dye ratio in capsules, applicability and limits of use of that type multi-component microencapsulated sensors are discussed.     

A hydrogen pump: Transfer of four hydrogens from a cyclohexane ring to a triple bond during a menthofuran/bromoacetylene adduct rearrangement

The cycloadducts of menthofuran with acylbromoacetylenes, (3-bromo-1,6-dimethyl-5,6,7,8-tetrahydro-2H-2,4a-epoxynaphthalen-4-yl)(aryl)methanones, rearrange (CHCl₃, reflux, 1 h) to 2-(2-acylethyl)benzofurans (along with the expected 2-bromo-3-hydroxy-4,7-dimethyl-5,6,7,8-tetrahydronaphthalene-1-yl)(aryl)methanones) via 2-acylethynylmenthofurans, thus indicating the exceptionally mild and rapid transfer of four hydrogens from a cyclohexane ring to a triple bond through the furan moiety in the key intermediate 2-acylethynylmenthofuran.     

Hydrogenation of C=C and C=N Bonds of the Amide-Imine Ligand in the Metal Coordination Sphere in the Reaction of Yttrium Bis(alkyl) Complex [2,6-iso-Pr2C6H3NC(=CH2)C(Me)=NC6H3-iso-Pr2-2,6]Y(CH2SiMe3)2(THF) with Molecular Hydrogen

Russian Journal of Coordination Chemistry - On treatment of the yttrium bis(alkyl) complex [ArNC(=CH2)C(Me)=NAr]Y(CH2SiMe3)2(THF) (I, Ar = C6H3-iso-Pr2-2.6) containing an amide-imine ligand, with...     

Poly[3,3-bis(azidomethyl)oxetane]–2,4-dinitro-2,4-diazapentane

Constructing phase diagrams for the mixtures of semicrystalline polymers and low molecular mass substances by DSC can meet with difficulties in the case of slow polymer crystallization. A problem of this kind is encountered for high-energy compositions poly[3,3-bis(azidomethyl)oxetane] (PBAMO)–2,4-dinitro-2,4-diazapentane (DNAP). In this study, the experimental phase diagram PBAMO–DNAP is constructed by an optical method, which makes it possible to visualize structural transformations. The kinetic studies by DSC and XRD reveal that 30–50 days of storing a homogenized PBAMO–DNAP mixture at room temperature are needed to attain stationary values of the crystallinity degree and heat of fusion. Even after that, the DSC method cannot deliver a solubility curve of DNAP in PBAMO, which is naturally generated by the optical method. This curve separates a domain of physical gels, effectively crosslinked by polymer crystallites and swollen with the plasticizer molecules, from a two-phase domain, in which the above gel reaches osmotic equilibrium with the pure plasticizer. It is also shown that the melting temperature of DNAP drops with growing the PBAMO content in the mixture, which is consistent with a decrease in the mean size of plasticizer crystals formed in polymer pores during the previous cooling.     

Guanidinate derivatives of rare-earth metals. The synthesis, properties, and molecular structures of the complexes {(Me3Si)2NC(NPri)2}3Nd, {(Me3Si)2NC(NCy)2}3Lu, and {(Me3Si)2NC(NPri)2}2HC(NPri)2}Nd

The reactions of anhydrous LnCl₃ (Ln = Nd or Lu) with three equivalents of {(Me₃Si)₂NC(NR)₂}Li (R = Prⁱ or Cy; Cy is cyclohexyl) in THF afforded the corresponding tris(guanidinate) derivatives of lanthanides {(Me₃Si)₂NC(NR)₂}₃Ln (Ln = Nd, R = Prⁱ, (1); Ln = Lu, R = Cy (2)), which were isolated after the recrystallization from hexane in 82 and 88% yields, respectively. The complex {(Me₃Si)₂NC(NCy)₂}₂{HC(NCy)₂}Nd (3) containing two guanidinate ligands and one formamidinate ligand was isolated in attempting to synthesize the bis(guanidinate) borohydride derivative by the reaction of {(Me₃Si)₂NC(N-Cy)₂}Na with Nd(BH₄)₃(THF)₂ (in a molar ratio of 2: 1) in THF. This complex is apparently formed as a result of the fragmentation and redistribution of the guanidinate ligands. The X-ray diffraction study showed that in the crystalline state compounds 1–3 are mononuclear complexes containing no coordinated Lewis bases.     

Mixed-ligand guanidinate derivatives of rare-earth metals. Molecular structures of { (Me3Si)2NC(N-cyclo-Hex)2}Y[N(SiMe3)2]2, [{ (Me3Si)2NC(N-cyclo-Hex)2}YbI(THF)2]2, and [{(Me3Si)2N} Y(THF)(µ-Cl)]2 complexes

The insertion of N,N′-dicyclohexylcarbodiimide at one of the Y-N bonds of the [(Me₃Si)₂N]₃Y complex in toluene at 70 °C afforded the monoguanidinate diamide derivative { (Me₃Si)₂NC(N-cyclo-Hex)₂}Y[N(SiMe)₃]₂ (1) (cyclo-Hex is cyclohexyl) in 72% yield. The reaction of equimolar amounts of sodium N,N′-dicyclohexyl-N″-bis(trimethylsilyl)guanidinate, which was prepared in situ from {(Me₃Si)₂N}Na and N,N′-dicyclohexylcarbodiimide, and YbI₂(THF)₂ in THF gave the [{(Me₃Si)₂NC(N-cyclo-Hex)₂}YbI(THF)₂]₂ complex (2). An attempt to use this procedure for the synthesis of the yttrium compound { (Me₃Si)₂NC(NSiMe₃)₂}₂YCl containing the sterically more hindered guanidinate ligand unexpectedly led to the formation of the diamide chloride complex [{(Me₃Si)₂N}₂Y(THF)(µ-Cl)]₂ (3). The structures of complexes 1–3 were established by X-ray diffraction. Compound 1 is mononuclear. Complexes 2 and 3 are dinuclear and contain two µ²-bridging halide ligands.     

Pattern shape control for heat treatment purification of electron-beam-induced deposition of gold from the Me2Au(acac) precursor

Gold structures can be created in a scanning electron microscope (SEM) from the Me(2)Au(acac) precursor by direct writing with the electron beam. The as-deposited purity is usually poor, and a common purification approach is a post-annealing step that indeed is effective but also induces a volume reduction because of carbon loss and an undesirable reconfiguration of the gold structure, resulting in the loss of the original shape. We studied the shape change as a result of such purification, and to minimize this effect, the application of a tantalum and chromium buffer layer was investigated. These buffer materials are well-known for their good adhesion properties. We confirm by dedicated SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM) analysis that, for the creation of a uniform Au structure, tantalum is a better buffer layer material than chromium. Post-annealing of the Au electron-beam-induced deposition (EBID) patterns for 1 h at 600 °C in air resulted in a dramatic purity increase (from 8-12 atomic % Au to above 92 atomic % Au). The uncovered part of the tantalum layer can be easily etched away, resulting in a well-defined, high-purity, gold structure.     

Synthesis of Cobalt Bis(Dicarbollide)—Curcumin Conjugates for Potential Use in Boron Neutron Capture Therapy

A series of novel cobalt bis(dicarbollide)—curcumin conjugates were synthesized. Two conjugates were obtained through the nucleophilic ring-opening reaction of the 1,4-dioxane and tetrahydropyran derivatives of cobalt bis(dicarbollide) with the OH group of curcumin, and using two equiv. of the oxonium derivatives, two other conjugates containing two cobalt bis(dicarbollide) units per molecule were obtained. In contrast to curcumin, the conjugates obtained were found to be non-cytotoxic against both tumor and normal cell lines. The analysis of the intracellular accumulation of the conjugates by flow cytometry showed that all cobalt bis(dicarbollide)—curcumin conjugates entered HCT116 colorectal carcinoma cells in a time-dependent manner. New non-cytotoxic conjugates contain a large amount of boron atoms in the biomolecule and can potentially be used for further biological research into boron neutron capture therapy (BNCT).