Synthesis,spectroscopic characterization and in vitro studies of antimicrobial activity of bis(diorganodithiocarbamato)organodithiocarbonatobismuth (III) complexes

A brief account of the synthesis, spectroscopic characterization and the antimicrobial (bacterial and fungal) behaviour of bis(diorganodithiocarbamato)organodithiocarbonatobismuth(III) complexes is presented. The reaction of bis(diorganodithiocarbamato)bismuth(III) chloride with potassium organodithiocarbonate in equimolar ratio yielded the corresponding mixed derivatives of the type [R′₂NCS₂]₂BiS₂COR [where, R′ = CH₃ and C₂H₅; R = Et, Prⁿ, Prⁱ, Buⁿ and Buⁱ]. These have been characterized by molecular weight determinations, melting points (only solid complexes) and elemental (C, H, N, S and Bi) analysis as well as spectral IR and NMR [¹H and ¹³C] studies. The antibacterial and antifungal activities of the free ligands and their bismuth complexes were found in vitro by the disc diffusion method. The complexes showed good antibacterial and antifungal effect on some selected bacterial and fungal strains. The antimicrobial activities of two standard antibiotics (Chloroamphenicol and Terbinafin) were also measured and compared with these complexes. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of annealing on calcium tungstate crystals

The influence of annealing in different atmospheres on absorption and luminescent properties of high-quality undoped CaWO₄ single crystals is presented. The decreasing of green emission intensity after annealing in oxygen and air have been revealed, while two well-defined maxima near 25,000 and 32,000 cm⁻¹ can be observed in the induced absorption spectra. These maxima are attributed to the interstitial oxygen, possibly in the form of the O⁻-centre. The increase of the blue/green luminescence ratio has been revealed after annealing in nitrogen while the crystal transparency remains unaffected. The possible ways to reduce slow green emission component without changing crystal absorption are shown. Structure of colour centres and the models of revealed processes are discussed.     

Local Trapping Centers in the Ceramics of Eulytines

Thermally stimulated luminescence (TSL) of ceramics having the structure of eulytine Bi₄X₃O₁₂ (X = Si, Ge, Zr) on exposure to x-ray irradiation in the temperature region 80–400 K is studied. An analysis of the forms of the TSL curves implies that the recombination processes in the TSL peaks at 149 and 212 K in Bi₄Si₃O₁₂ ceramics and at 143 and 230 K in Bi₄Ge₃O₁₂ ceramics can be described by the linear kinetics. The spectral composition of TSL of the ceramics obtained is investigated, and the activation energy and frequency factors which correspond to the TSL maxima are determined by various methods. Based on common spectral and energy characteristics of TSL, a conclusion concerning the connection of TSL with recombination processes in common structural complexes of BiO₆ ^9– is drawn.     

Crystallographic report: Bis[(nitro)bis(dithiotetrahydropyrrolocarbamato) bismuth(III)]

The loosely associated centrosymmetric structure of [Bi(S₂CNC₄H₈)₂(NO₃)]₂ features chelating dithiocarbamate and nitrate ligands, as well as weak intermolecular Bi? S interactions, so that a distorted pentagonal bipyramidal S₅O₂ coordination geometry results. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of 1-tetralones by intramolecular Friedel-Crafts reaction of 4-arylbutyric acids using Lewis acid catalysts

Intramolecular Friedel-Crafts reaction of 4-arylbutyric acids efficiently proceeded in the presence of catalytic amounts of Lewis acids such as Bi(NTf₂)₃ and M(OTf)₃ (M=Bi, Ga, In and rare-earth metals) to form 1-tetralones. Chroman-4-one and thiochroman-4-one were also obtained in good yields from 3-phenoxypropionic acid and 3-phenylthiopropionic acid, respectively.     

Modification of scintillation characteristics of CdWO4 by doping with different ions

We studied doping CWO with several different dopant ions in order to create new heavy and fast scintillators by quenching the efficient but slow scintillation in CWO. Transmittance, excitation–emission spectra, decay time and the light yield were measured for the dopants of Cs, La, Si, Bi, Na, Nb and Pb. None of them caused efficient quenching. Trivalent ions seem to degrade crystal transparency, while monovalent ions do not seem to cause quenching. While heavy doping of Pb causes quenching to some extent, crystal growth is not easy for heavy doping. Heavy doping of the same wolframite structure crystal should be further examined.     

Sulfated tungstate as hydroxyl group activator for preparation of benzyl,including p-methoxybenzyl ethers of alcohols and phenols

Sulfated tungstate was found to be an effective heterogeneous and reusable catalyst for hydroxy group activation–mediated preparation of benzylic ethers including p-methoxybenzylic ethers of a wide range of alcohols and phenols under mild reaction conditions.     

BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂的制备及光催化性能研究

以Bi(NO_3)_3·5H_2O和NH_4VO_3为原料,控制水溶液介质p H及反应时间,采用水热合成法制备钒酸铋(BiVO_4)及其复合物(BiVO_4/Bi_6O_6(OH)_3(NO_3)_3).利用X-射线粉末衍射、扫描电子显微镜和紫外-可见漫反射吸收光谱等手段对制备的样品进行了物理表征,结果表明,在控制反应时间为1 h,介质p H值在1.14~9.01之间时,制备的样品为BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合物,当p H值增加至10.92时为纯BiVO_4;控制介质p H为7.17,反应时间在1~12 h之间时得到BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂,反应时间为18 h时为纯BiVO_4.在可见光(λ≥400 nm)照射下,以有机染料罗丹明B(Rhodamine B,Rh B)为底物,研究不同条件制备的BiVO_4或者复合物为光催化剂的光催化特性,发现p H=7.17,水热反应12 h得到的催化剂(BiVO_4/Bi_6O_6(OH)_3(NO_3)_3)光催化降解活性高于对照制备的纯BiVO_4.同时在可见光照射下,BiVO_4/Bi_6O_6(OH)_3(NO_3)_3亦可以有效降解无色小分子2,4-二氯苯酚(2,4-Dichlorophenol,2,4-DCP),说明氧化过程涉及到光催化过程.分析BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂对Rh B光催化降解过程中活性物种,表明在降解过程中主要涉及空穴和超氧氧化,O_2·~-起主要作用.     

Determination of cadmium residues in bee products using a ‘lab-made’ bismuth bulk electrode

Raw propolis and bee pollen has been widely used in different areas such as medicine, food and apitherapy because they have biological and medicinal properties. The beneficial effects of both bee products for human health include antibacterial, antiviral, antimicrobial and anti-inflammatory properties. However, hives exposure to heavy metals, due beekeeping practices and environment, is one of the problems facing beekeepers. The presence of cadmium in bee products should be controlled, because of its high toxicity. A lab-made Bismuth Bulk Electrode (BiBE) was developed for cadmium residue determination in Argentinean bee products such as raw propolis and bee pollen employing square wave anodic stripping voltammetry (SWASV) as electrochemical technique. The SWASV parameters were optimised based on a 2 ⁵ factorial design. The method presents a linear range from 2.00 to 100.0 µg L^?1 of Cd (II) with a limit of detection (LOD) and a limit of quantitation (LOQ) of 0.78 µg L^?1 and 2.61 µg L^?1, respectively. The repeatability was 8.03%, calculated as the relative standard deviation. Recovery experiments were performed using spiked raw propolis and bee pollen samples with standard deviation values from 1.16% to 7.20%. The BiBE is easy and fast to elaborate and the propose method is environmentally friendly and low cost. Then, it can be considered as a good alternative to the quality control of bee products due to its importance in the beekeeping industry.     

Solvent‐Driven Reductive Activation of CO2 by Bismuth: Switching from Metalloformate Complexes to Oxalate Products

In this work, we investigated how the reductive activation of CO₂ with an atomic bismuth model catalyst changes under aprotic solvation. IR photodissociation spectroscopy of mass‐selected [Bi(CO₂)_n]^? cluster ions was used to follow the structural evolution of the core ion with increasing cluster size. We interpreted the IR spectra by comparison with density‐functional‐theory calculations. The results show that CO₂ binds to a bismuth atom in the presence of an excess electron to form a metalloformate ion, BiCOO^?. Solvation with additional CO₂ molecules leads to the stabilization of a bismuth(I) oxalate complex and results in a core ion switch.