Fluorescence Probe Studies of Ionic Micelles in Concentrated Salt Solutions

We have investigated the effect of salt concentration and temperature on the average aggregation number and micro-polarity of the interior of micelles of sodium dodecyl sulfate (SDS). sodium tetradecyl sulfate (STDS) and lithium dodecyl sulfate (LiDS). The transient fluorescence decay of micelle-solubilized pyrene has been measured and analyzed. An exponent weighted average aggregation number <n>_e was obtained by this technique. For SDS and STDS in NaCl solution, <n>_e increases as the temperature is lowered or salt concentration is increased <n>_e increased from ～ 50 to ～ 250 over [NaCl] = 0 to 0.8 M. Due to the strong counterion binding of lithium in the micellar solution, the LiDS micelle is much, smaller and does not increase appreciabily even at [LiCl] =0.8 M. From the fluorescence spectrum fine structure of pyrene and the fluorescence decay of the monomer and excimer, we can understand the local polarity and the water penetration to the interior of the micelle upon addition of salts and with changing temperature. The interior of the micelle becomes more nonpolar as the salt concentration is increased and the temperature is lowered. A complete kinetic analysis of the time–dependence of the fluorescence is given. The kinetic analysis is in agreement with the results reached by fluorescence spectral analysis.     

Synthesis and manganese complexes of pentagonal bipyramidal ligands: N,N′-disubstituted pentaaza macrocycles

Two novel heptadentate ligands, pentaaza macrocycles with two pendant xpyridyl and phenol groups, were prepared and the crystal structure of the manganese(II) complex of N,N′-bis(2-pyridylmethyl)-pentaaza macrocycle revealed a pentagonal bipyramidal geometry.     

Elemental analysis of Korean women’s blood serums using instrumental neutron activation analysis

Instrumental neutron activation analysis was used to assess the concentration of the inorganic trace elements in Korean women’s blood serums. It was found that a high concentration of Na and Cl incurs an analytical interference, but the 12 elements such as Br, Ca, Cl, Co, Cr, Cs, Fe, K, Na, Rb, Se and Zn could be determined under the condition of an interference minimization. Serum samples collected from 63 women were analyzed and the concentration level and range of the elements were evaluated. NIST SRMs were analyzed simultaneously for quality control. The average values of the Na and Cl determined in the serum samples were 3,365 and 3,533 mg/l, Ca was 96.4 mg/l and K was 191 mg/l. Besides, Br, Se and Zn have a concentration level of 6.46, 0.13 and 0.98 mg/l, respectively. It was found that there is no significant difference between the present values and the reported values.     

Synthesis of 3,5,7-Trioxapentacyclo[7.2.1.02,8.04,11.06,10]dodecane. A Novel Diacetal Trioxa-Cage

3,5,7-Trioxapentacyclo[7.2.1.0^2,8.0^4,11.0^6,10]dodecane, the parent compound of novel diacetal trioxa-cages, was synthesized from maleic anhydride cyclopentadiene adduct 1 by a four-step sequence. Attempts for the synthesis of monoaza dioxa-cage 12 failed. Ozonolysis of compound 9 in CH₂Cl₂-EtOH(1:1) at ?78°C followed by reduction with Me₂S gave 13 in 65% yield.     

A catalytic synthesis of thiosilanes and silthianes: palladium nanoparticle-mediated cross-coupling of silanes with thio phenyl and thio vinyl ethers through selective carbon-sulfur bond activation

Palladium nanoparticles generated in situ from N,N-dimethyl-acetamide (DMA) solutions of PdX(2) (X = Cl(-), OAc(-), OCOCF(3)(-)) or Pd(2)(dba)(3) by reduction with alkyl silanes R(3)SiH (R = Me, Et, i-Pr, t-Bu) are selective catalysts for the cross-coupling of the silanes R(3)SiH with phenyl and vinyl thioethers forming the corresponding thiosilanes and silthianes in high yields and under mild conditions. The method is applicable to phenyl thioglycosides, giving access to thiosilyl glycosides a new class of sugar derivatives.     

The use of a chelating resin column for preconcentration of trace elements from sea-water in their determination by neutron-activation analysis

A Chelex-100 resin column has been employed for the preliminary concentration of trace elements in water samples before their determination by neutron-activation analysis. The column, filled with a 1:1 mixture of the resin (50-100 mesh) and Pyrex glass powder of the same mesh-size, is shown to maintain a constant flow-rate and give reproducible results. By a combination of preconcentration and neutron-activation analysis it is possible to determine Ba, Ca, Cd, Ce, Co, Cr, Cu, Fe, La, Mg, Mn, Sc, U, V and Zn in sea-water and/or fresh water simultaneously at the parts per milliard level.     

Self-assembly between silver(I) and di- and tri-2-pyridines with flexible spacer: formation of discrete metallocycle versus coordination polymer

The self-assembly of metallosupramolecules from reactions of flexible 2-pyridyl ligands and silver salts is described. When 1,3-bis(2-pyridyl)propane (L1), tris[(2-pyridyl)methyl]methane (L2), and 1,3-bis(2-pyridyl)-2-tolylpropane (L3) are used in combination with silver ions, novel discrete metallocyclic complexes are formed in crystals. Moreover, the self-assembly of 1,3-bis(2-pyridyl)-2-phenylpropane (L4) with silver nitrate yields a coordination polymer. The examination of its solution shows that this coordination polymer is formed via the solution-based discrete metallocyclic species.     

Superheating Limit of Boiling n-Hexane Spinodal Decomposition Versus Nucleation Process

Two predicative theories for superheating limits of a boiling liquid are considered in this work. In the nucleation picture, classical homogeneous nucleation theory is used to calculate superheating temperature at various pressures. In spinodal decomposition picture, stability limits are taken as the superheating temperature. A perturbed-hard chain equation of state was developed and used for the purpose of calculating mechanical stability limit. Calculations are done for the case of normal hexane at different pressures and compared with experimental results. Classical nucleation theory gives good prediction at negative and smaller pressures. While near critical pressure, spinodal picture seems to be more accurate.     

Dicobalt octacarbonyl-catalyzed tandem

Novel 5-5-6 tricyclic compounds containing cyclopentenone have been constructed by the dicobalt octacarbonyl catalyzed tandem [2 + 2 + 1] and [2 + 2 + 2] cycloaddition reaction between a diyne and two phenylacethylene under CO pressure.