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In this study, manganese (Mn) doped Calcium Tetraborate (CaB4O7) samples were prepared by the wet chemical method. Under beta irradiated, CaB4O7:Mn showed thermally stimulated luminescence (TSL) glow peaks at approximately 85 °C and 220 °C with a heating rate of 5 °C/s. Peak shape (PS) and various heating rates (VHR) methods were applied for determining the trap parameters such as order of kinetic (b), activation energy (E) and frequency factor (s). The results indicate that the main dosimetric peak of CaB4O7:Mn follows the second-order kinetic model. The thermal fading ratio of the material is around 15% at the end of one month period of storage. The results of the TL studies carried out on the CaB4O7:Mn dosimeter revealed that it has high sensitivity, which makes it very valuable in various dosimetric applications like space, medical, personal dosimetry and dating. Radioluminescence (RL) of CaB4O7:Mn was also studied. It is shown that the RL spectrum contains a wide band centered at 530 nm assigned to Mn2+ ion emission. A broad band emission feature peaked at 350 nm assigned to the non-bridging oxygen hole center (NBOHC) is also discussed and a model is proposed to explain this broad band feature.

We report on two approaches for the synthesis of new 2-amino-3-cyano/alkoxycarbonyl-8H-thieno[2,3-b]indoles 5 and another one for the synthesis of 2-N,N-dialkylamino-3-cyano/aryl-8H-thieno[2,3-b]indoles 16, based either on acetylindoxyl 1 and (1-acetyl-1H-indol-3-yl)malononitrile/cyanoacetates 14 or 2-bromoacetylindoxyl 2 transformations. A new, simple, rapid, and efficient method for the synthesis of valuable key intermediate malononitrile/cyanoacetates 14 based on acetylindoxyl 1 condensation with malononitrile or cyanoacetates in the presence of triethylamine has been developed. A number of synthetic procedures for the preparation of thioacetamides 6, 1-acetylthioisatin 8, and 2,2-disubstituted indoxyls 13 have been elaborated during the synthesis of thieno[2,3-b]indoles. Thioacetamides 6 have been shown as novel agents active against Mycobacterium tuberculosis H37Rv, the cause of tuberculosis, with minimal inhibitory concentration values ranging between 5 and 21 μg/mL.

Various oxadiazolyl-(X) and azetidinyl-derivatives (XIV) of benzimidazole are synthesized and evaluated for their antibacterial activity.

Arrhenius rate expressions were determined for the abstraction of hydrogen atom from thiophenol and hexanethiol by the octanethiyl radical at 25-100 {degrees}C in nonane. Octanethiyl radicals were produced by steady-state photolysis of octyl thiobenzoate. Analysis of octyl disulfide and octanethiyl radical. For hexanethiol, log (k{sub abs}/K{sub t}{sup 1/2}) = (2.94 {plus_minus} 0.29) - (3.84 {plus_minus}0.41)/0, and for thiophenol, log (k{sub abs}/k{sub 5}{sup 1/2}) = (2.56 {plus_minus} 0.19) - (2.88 {plus_minus} 0.28)/0;0=2.3RT kcal/mol. Combining these expressions with the Smoluchowski expression for self-termination of octanethiyl in nonane, log (k{sub t}{sup 1/2}) = 5.96 - 1.335/0, which employs experimental diffusion coefficients of octanethiol and a spin selection factor {sigma} = 1, yields, for thiophenol, log (k{sub abs}/M{sup {minus}1}s{sup {minus}1}) = (8.52 {plus_minus} 0.18) = (4.22 {plus_minus} 0.27)/0, and for hexanethiol, log (k{sub abs}/M{sup {minus}1} s{sup {minus}1}) = (8.90 {plus_minus} 0.29) = (5.18 {plus_minus} 0.41)/0 (errors are 2{sigma}). The rate of disappearance of octanethiyl/diphenylketyl radical pairs in SDS micelles, determined by nanosecond optical spectroscopy, was found to be unchanged in a 700-G magnetic field, providing evidence for rapid intersystem crossing of sulfur-centered radical pairs and support for the assignment of {sigma} = 1 above. Ab initio electronic structure calculations on the reaction HS{sup {lg_bullet}}more » + HSH {r_arrow} HSH + {sup {lg_bullet}}SH, performed at SCF and correlated levels, predict an activation barrier of {Delta}H{sub 298} {sup {double_dagger}}= 4.6 kcal/mol, in close agreement with the experimental barrier for the octanethiyl + hexanethiol reactions. 43 refs., 5 figs., 4 tabs.« less

Repeating glycosidic linkages of oligosaccharides can be synthesized by solid-phase methods. Glycals were attached to a polystyrene copolymer with a silyl ether bond and were activated to function as glycosyl donors with 3,3-dimethyldioxirane. Glycosidation was performed by reactions with a solution-based acceptor (itself a glycal). Excess acceptor and promoter were removed by rinsing after each coupling, and the desired oligosaccharides were then easily obtained from the polymer by the addition of tetra-n-butylammonium fluoride. By this method, glycosidations are stereospecific and interior deletions are avoided.

A new series of complexes of the type cis-PtL2X2 [where L is a monodentate AQ-Y(CH2)nNH2 and L2 is a bidentate AQ-Y(CH2)nNH(CH2)2NH2; AQ = anthraquinone, X = Cl, I, Y = NH, O] in which anthraquinone intercalators are tethered to the cis-PtCl2 unit via an (aminoalkyl)amino, (oxyalkyl)amino, or polyethylene glycol (aminoethyl)amino linker chains was prepared and screened in vitro against P388 leukemia. In vivo toxicity studies were carried out on selected complexes. All complexes were characterized by means of elemental analysis, 195Pt NMR spectroscopy, and FTIR. The 1:1 Pt-intercalator complexes displayed much higher in vitro cytotoxic activities than the 1:2 Pt-intercalator complexes. The dichloride complexes were consistently more active than their diiodide counterparts. Among the 1:1 Pt-intercalator complexes those with the shorter linker chains (n = 2, 3) exhibited the highest cytotoxic activities. Three compounds, [[2-[[2-(anthraquinon-1- ylamino)ethyl]amino]ethyl]amine-N,N']dichloroplatinum(II), [[2-[[3-(anthraquinon-1-ylamino)propyl]amino]ethyl]amine- N,N']dichloroplatinum(II), and [[2-[[3-anthraquinon-1- yloxy)propyl]amino]ethyl]amine-N,N']dichloroplatinum(II), were as active in vitro as cisplatin (ED50 = 2-4 x 10(-7) M) while on a molar basis their acute in vivo toxicity was significantly lower than that of cisplatin. In vivo screening against P388 leukemia indicated that these complexes have activity comparable to cisplatin.

Bi/Cr and Bi/Fe bimetallic clusters are produced in a pulsed nozzle cluster source by laser vaporization of solid bismuth and coincident photolysis of iron or chromium carbonyl vapor. Neutral clusters are photoionized at 193 nm with an ArF excimer laser in a reflectron time-of-flight mass spectrometer. The resulting cations are mass-selected and photodissociated at various ultraviolet wavelengths. Photodissociation channels indicate that heteronuclear bismuth-transition metal bonding is comparable energetically to corresponding homonuclear interactions in these systems. Lower limits on dissociation energies (D{sub 0}{double prime}) are obtained for Bi-Fe ({ge} 1.85 eV), Bi{sup +}-Fe ({ge} 1.85 eV), Bi-Cr ({ge} 2.58 eV), and Bi-Cr{sup +} ({ge} 2.06 eV).

Reduction of the oxoindan acid (9) by potassium in liquid ammonia followed by in situ alkylation with 3-methylbut-2-enyl bromide furnished enol ether (14) which was transformed into the acetal (17) and thence aldehydes (18; R = COCH3 and COCHCl2). Acid- catalysed aldol reactions then afforded the ethanoindene derivatives (19; R=COCH3 and COCHCl2). Further elaboration gave carbinol (28) which is envisaged as an intermediate for the total synthesis of the diterpenoid antheridiogens obtained from gametophytes of the fern genus Anemia, including acid (2). The relative stereochemistry of acetal (17) was established by X-ray crystallographic analysis.

The stereoselectivity of methylation and aldol condensation of camphor and derivatives is determined by the presence or absence of a C(7) syn-methyl group and (or) C(5) and C(6) endo-hydrogen atoms. Key words: camphor, C(3) methylation, C(3) aldol.

An efficient NMR determination of the enantiomeric excess of C 2 -symmetric 1,2-diamines can be achieved by coordination of the bidentates to the optically active forms of the diamagnetic [dimethyl(1-(2-naphthyl)ethyl)aminato- C 2 , N ]palladium(II) units.

Mono- and diazo compounds of 5-(2-nitrophenyl-azo-)2,2',4,4'-tetrahydroxy-benzophenone and 5,5'-di( 2-nitrophenyl-azo- )2,2',4,4'-tetrahydroxybenzo-phenone have been synthesized by the azo-coupling reaction of o-nitrobenzenediazonium chloride with 2,2',4,4'-tetrahydroxyhenzophenone. Esterification of the mono-azo compound with acryloyl and methacryloyl chloride gave the monomeric acryloyloxy and methacryloyloxy azo-pigments in 57 and 59% yield. Reductive cyclization of the mono-azo compound gave a yellow product containing two types of ultra-violet absorbers, i.e. benzophenone and benzotriazole units. All compounds were characterized by their IR, UV. and 1H NMR.

The synthesis of palladium and platinum complexes of (±)- Ph 2 ECH 2 CH 2 S(O)Me (EP, As) is described. A single crystal X-ray diffraction study of [(±)-Ph 2 PCH 2 CH 2 S(O)MePdCl 2 ] reveals a square-planar geometry at the central atom which is attached by a chelate ring via the PS donors of the sulfinyl-substituted ligand. Similar structures are assigned to all four complexes by 1 H NMR spectroscopy in d 3 -acetonitrile solutions. Oxygen-metal bonds are not involved in these molecules.

We report a two-step synthesis for N-aryl- and N-alkyl-substituted 4-piperidones, in which the N substituent can easily be varied. A number of intramolecular donor-acceptor systems was synthesized from these piperidones by conversion of the carbonyl functionality. The influence of the N-aryl donor on the electronic absorption and fluorescence spectra was investigated systematically. It was concluded that some systems can be used as efficient fluorescent probes with a high sensitivity for solvent polarity.

This paper describes a concise and effective synthesis of methyl α-phosphonoaryl acetates, effected by reacting α-phosphono carbanions with methyl chloroformate. Yields are high, and the purification of the products is readily achieved with column chromatography.

EPR spectroscopy has been used to identify and characterize the paramagnetic adducts of small free radicals with C60 through measurements of the hyperfine interactions of protons and13C nuclei. The initially formed mono-radical adducts (RC60) have unpaired spin density localized near the point of attachment of the radical. Generally, they are in thermal equilibrium with their diamagnetic dimer, and have a surprisingly large barrier to internal rotation about the new bond. The tri- and penta-radical adducts have electronic structures similar to those of allyl and cyclopentadienyl radicals, respectively.

Organoimido complexes of Group-VI transition metals were found to catalyze ring-opening of epoxides by trimethylsilyl azide and amines with good regioselectivities.