Reinvestigation of the reaction of [Ru3(CO)12] with 2-mercaptobenzothiazole: X-ray structure of [(μ-H)2Ru3 (μ-η2-C7H4NS2)(μ3-η2-C7H4NS2)(CO)7]

Treatment of Ru₃(CO)₁₂ with 2-mercaptobenzothiazole at 68°C gave the known compound [(-H)Ru₃(₃-²-C₇H₄NS₂)(CO)₉] 1 and the new compound [(-H)₂Ru₃(-²-C ₇H₄NS₂) (₃-²-C₇H₄NS₂)(CO)₇] 2 in 15 and 10% yields respectively. Compound 2 has been characterized by elemental analysis, infrared, ¹H NMR and mass spectroscopic data together with single crystal X-ray crystallography. It crystallizes in the monoclinic space group C2/c with a = 31.662(6), b = 14.577(3), c = 11.602(2) Å, = 104.15(3)°, Z = 8, and V = 5192.4(2) ų. The compound consists of a Ru₃ triangle with three different Ru-Ru bond lengths [2.75264, 2.79084, 2.97604 Å] and the two 2-mercaptobenzothiazole ligands are differently attached to the metal atoms. Compound 2 is also obtained by the reaction of 1 with excess 2-mercaptobenzothiazole at 68°C.     

Preparation of Mesoporous Titania by Templating with Polymer and Surfactant and its Characterization

Mesoporous titania was obtained by gelation from Ti-alkoxide in alcoholic solutions with addition of polymer and/or surfactant. The structure and surface morphology of the gels were characterized by N₂-adsorption measurements, scanning electron microscopy and X-ray diffraction. The specific surface area and pore volume of the gels can be increased with addition of hydrophilic polymer such as polyethyleneglycol. Surfactants like cetyltrimetylammoniumchloride are effective to control the pore size and to increase the pore volume and surface area. The surface morphology of the gels can be modified by the mixing method with polymer and/or surfactant. The effects of the templating on pore size distribution, pore shape, surface area and crystallization behaviors have been discussed.     

Preparation of micron-sized composite polymer particles containing hydrophilic 2-hydroxyethyl methacrylate and their biomedical applications

Micron-sized polystyrene or PS particles were first prepared by dispersion polymerization. Then a series of polystyrene/poly(styrene-2-hydroxyethyl methacrylate) or PS/P(S-HEMA) composite polymer particles was prepared by seeded copolymerization using different amounts of 2-hydroxyethyl methacrylate (HEMA) at the constant core/shell ratio of 1/0.5. The produced PS seed and composite polymer particles were characterized by transmission electron microscopy. Adsorption behaviors of some biologically active macromolecules were studied under similar conditions. In each case the magnitude of adsorption on composite polymer particles decreased with the increase in HEMA content in the recipe, which means that the hydrophobic interaction between the surface of the particles and biomolecules decreased. The specific activities of trypsin aqueous solution and adsorbed trypsin on PS seed and composite polymer particles prepared with different HEMA contents were also measured and compared. The activity of adsorbed trypsin on composite polymer particles improved significantly with the incorporation of hydrophilic HEMA.     

Synthesis and antimicrobial activities of isomers of N(4),N(11)-dimethyl-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane and their nickel(II) complexes

The reactions of two isomers of 3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (differing in the orientation of the methyl groups on the chiral carbon atoms), designated as L(B) and L(C), with CH(3)I in the ratio of 1:4 resulted in the substitution of the N(4) and N(11) protons by CH(3) groups, forming the dimethyl derivatives L(BZ) and L(CZ), respectively. These ligands, on interaction with nickel(II) acetate tetrahydrate and subsequent addition of lithium perchlorate, produce square-planar yellow [NiL(BZ)][ClO(4)](2) and orange [NiL(C'Z)][ClO(4)](2). These nickel complexes undergo axial ligand addition reactions with NCS(-), Cl(-), Br(-), and I(-) as X(-) to form six-coordinate trans-diisothiocyanato, -dichloro, -dibromo, and -diiodo complexes of formula [NiLX(2)], where L = L(BZ) or L(C'Z), and X = SCN, Cl, Br, or I. All these compounds have been characterized on the basis of analytical, spectroscopic, conductometric, and magnetochemical data. The structures of L(BZ) and two variants of [Ni"L(BZ)"][ClO(4)](2) (crystallizing in the space group P2(1)/n and Pn, respectively; "L(BZ)" symbolizes partially methylated ligand) have been determined by single-crystal X-ray analyses. The antifungal and antibacterial activities of these compounds have been studied against some phytopathogenic fungi and bacteria.     

Heterogeneous Heck reaction catalysed by silica gel-supported 1,2-diaminocyclohexane–Pd complex

A 1,2-diaminocyclohexane–Pd complex was immobilized onto the surface of silica gel and investigated as a catalyst for Heck coupling reactions. The immobilized catalyst exhibited high catalytic activity in the coupling of activated and nonactivated aryl substrates with various acrylates. Moreover, the catalyst was air-stable that could be recycled and reused without significant loss of catalytic activity.     

Perturbations of the periodicity of plant leaflet oscillations caused by visible light

Lateral leaflet movements in the presence of blue and white light stimuli in the plant Desmodium gyrans have been studied. A strong effect, namely, the reduction of amplitude of the lateral leaflet movement and thus a shortening period was observed. The oscillations regained their same regularity over a few cycles after the stimulus was removed and they quickly halted when the lateral leaflets were exposed to a light of higher intensity. However, the blue light was found to be more effective than the white light in the perturbation of leaflet oscillations. The results were discussed by reviewing the investigations performed in this plant with other stimuli.     

Photon energy dependence of the spin polarization

Spin polarization in semiconductors was investigated by pump-probe measurements, where the transmissions of the samples were monitored with probe pulses with same and opposite circular polarizations. The spin polarization as a function of the pump-probe delay was estimated, and the polarization was found to decay in a sub-ns timescale. It was also found that the polarization depends strongly on photon energy of the pump beam. The pumping energy dependence of the spin polarization was discussed based on the inter-band transition probabilities.     

Preparation and Characterization of Porous Titania by Modified Sol-Gel Method

Mesoporous titania, especially anatase, is attractive due to its potential applications. A novel method to control pore structure of titania, surfactant- or polymer modification, is proposed. The wet gels and gel films, prepared from Ti(O-nC₄H₉)₄ were dried at 90°C and annealed at 500°C after immersion in surfactant or polymer solutions, and mesoporous anatase was obtained. The pore size, pore volume and specific surface area of the surfactant-modified bulk gels, estimated from N₂ absorption-desorption curves, are more than twice larger than those of the gels without modification. The pore size of the surfactant-modified gel films, observed by SEM, are similar to that of the bulk gels. The pore size obviously depended on the size of micelles. The pore size of the gels modified with hydrophilic polymers hardly increased, but the pore volume and the specific surface area increased.     

Elemental analysis in bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis

The concentration of rare earths and other elements have been determined in the bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis (INAA). The samples and the standards soil-5, soil-7, coal fly ash and pond sediment were prepared and simultaneously irradiated for short and long time at the TRIGA Mark-II research reactor facility of Atomic Energy Research Establishment, Savar, Dhaka. The maximum themal neutron flux was of the order of 10¹³ n·cm^–2·s^–1. After irradiation the radioactivity of the product nuclides was measured by using a high resolution high purity germanium detector system. Analysis of -ray spectra and quantitative analysis of the elemental concentration were done via the software GANAAS, it has been possible to determine the concentration level of 27 elements including the rare earths La, Ce, Sm, Eu, Tb, Dy and Yb and uranium and thorium.