Primary decomposition and the fractal nature of knot concordance

For each sequence P=(p₁(t),p₂(t),...){\mathcal{P}=(p_1(t),p_2(t),\dots)} of polynomials we define a characteristic series of groups, called the derived series localized at P{\mathcal{P}}. These group series yield filtrations of the knot concordance group that refine the (n)-solvable filtration. We show that the quotients of successive terms of these refined filtrations have infinite rank. The new filtrations allow us to distinguish between knots whose classical Alexander polynomials are coprime and even to distinguish between knots with coprime higher-order Alexander polynomials. This provides evidence of higher-order analogues of the classical p(t)-primary decomposition of the algebraic concordance group. We use these techniques to give evidence that the set of smooth concordance classes of knots is a fractal set.     

Oxidative fragmentation of 3-aryl-1-(tetrazol-5′-yl)triazenes: a new route to aryl diazocyanides.

Oxidation of 3-Aryl-1-(tetrazol-5′-yl)triazenes with Pb(OAc)₄ resulted in a fragmentation and gave aryldiazocyanides.     

Vibrational coherence from the dipyridine complex of bacteriochlorophyll a: intramolecular modes in the 10-220-cm(-1) regime, intermolecular solvent modes, and relevance to photosynthesis

We present the first observations of vibrational coherence in the 10-220-cm-1 region from bacteriochlorophyll a (BChl) in solution. A distinction can be made for the first time between BChl's intramolecular normal modes and intermolecular modes between BChl and solvent. The results show that the low-frequency vibrations that accompany the initial electron-transfer reaction from the paired BChl primary electron donor, P, in photosynthetic reaction centers arise predominantly from intramolecular modes of histidine-ligated BChl macrocycles. The results also suggest that polar-solvent interactions can significantly perturb the electronic properties of BChl in a manner that might have important functional consequences.     

Synthesis and characterization of cyano complexes of oxotungsten(IV) with morpholinomethyl urea and related ligands

The synthesis and characterization of complexes, (Ph₃P)₂NH₂[WO(CN)₃L-L] · 3H₂O and Cs[WO(CN)₃L-L] · H₂O (where L-L = morpholinomethylurea, morpholinomethylthiourea, piperidinomethylurea, piperidinomethylthiourea, pyrrolidinomethylurea, and pyrrolidinomethythiourea) are presented. The complexes have been prepared by the reaction of K₃Na[WO₂(CN)₄] · 6H₂O with morpholinomethylurea and related ligands in aqueous solution around a pH of 7. These have been isolated as bis(triphenylphospine)imminium or cesium salts. The complexes have been characterized by elemental analysis, ℝ, UV-Vis spectra, magnetic susceptibility and conductivity measurements in addition to TGA/DTA The text was submitted by the authors in English.     

The effect of inclusion inβ-cyclodextrin on the chemistry of peroxides: Reactions of radicals withβ-cyclodextrin

Studies by electron paramagnetic resonance (EPR), differential scanning calorimetry, thermogravimetric analysis, HPLC and NMR showed that radicals produced by thermolysis and photolysis of benzoyl peroxide,t-butyl peroxide and cumene hydroperoxide included in-cyclodextrin (-CD), undergo significant reaction with the-CD. The formation of-CD radicals was observed by EPR. Products formed by addition of radicals to-CD were also observed. Such host:guest radical reactions explain the reported stabilization of peroxides, found with-CD inclusion, as being primarily due to the interruption of chain reactions by trapping of the chain carriers. A small increase in activation barrier for cleavage of the included peroxide in-CD was also observed.     

A Microwave‐Accelerated Esterification of α,β‐Unsaturated Acids with Alkyl or Aryl Carbonochloridate and Triethylamine in Acetonitrile as a Novel Esterifying Reagent Mixture

An efficient synthesis of α,β‐unsaturated esters by treatment of the corresponding acids with alkyl or aryl carbonochloridate, triethylamine, and acetonitrile was accomplished for the first time under microwave irradiation for 10 min. The esters 1b – 24b were isolated in 71–97% yield.     

Shrink-wrap vesicles

We describe a simple approach to the controlled removal of molecules from the membrane of large unilamellar vesicles made of fatty acids. Such vesicles shrink dramatically upon mixing with micelles composed of a mixture of fatty acid and a phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)), as fatty acid molecules leave the vesicle membrane and accumulate within the mixed micelles. Vesicle shrinkage was confirmed by dynamic light scattering, fluorescence recovery after photobleaching of labeled vesicles, and fluorescence resonance energy transfer between lipid dyes incorporated into the vesicle membrane. Most of the encapsulated impermeable solute is retained during shrinkage, becoming concentrated by a factor of at least 50-fold in the final small vesicles. This unprecedented combination of vesicle shrinkage with retention of contents allows for the preparation of small vesicles containing high solute concentrations, and may find applications in liposomal drug delivery.     

Dipyridinium tetraisothiocyanatodioxotungstate(VI) and related compounds

Eight tetraisothiocyanatodioxotungstate(VI) salts with general formula, (BH)₂[WO₂(SCN)₄] (where B = pyridine, piperidine, quinoline, isoquinoline, 2-, 3-, and 4-picolines) are reported. These salts have been prepared by the reaction of sodium tungstate dihydrate with ammonium thiocyanate in the presence of HCl and isolated as pyridinium or related salts. The compounds have been characterized by elemental analysis, IR and electronic absorption spectra, conductance and magnetic susceptibility measurements, TGA/DTA, and molecular modelling studies The text was submitted by the authors in English.     

Thiol- and thioether-based bifunctional chelates for the {M(CO)3}+ core (M = Tc, Re)

By analogy to the recently described single amino acid chelate (SAAC) technology for complexation of the {M(CO)3}+ core (M = Tc, Re), a series of tridentate ligands containing thiolate and thioether groups, as well as amino and pyridyl nitrogen donors, have been prepared: (NC5H4CH2)2NCH2CH2SEt (L1); (NC5H4CH2)2NCH2CH2SH (L2); NC5H4CH2N(CH2CH2SH)2 (L3); (NC5H4CH2)N(CH2CH2SH)(CH2CO2R) [R = H (L4); R = -C2H5 (L5). The {Re(CO)3}+ core complexes of L1-L5 were prepared by the reaction of [Re(CO)3(H2O)3]Br or [NEt4]2[Re(CO)3Br3] with the appropriate ligand in methanol and characterized by infrared spectroscopy, 1H and 13C NMR spectroscopy, mass spectrometry, and in the case of [Re(CO)3(L2)] (Re-2) and [Re(CO)3(L1)Re(CO)3Br2] (Re-1a) by X-ray crystallography. The structure of Re-2 consists of discrete neutral monomers with a fac-Re(CO)3 coordination unit and the remaining coordination sites occupied by the amine, pyridyl, and thiolate donors of L2, leaving a pendant pyridyl arm. In contrast, the structure of Re-1a consists of discrete binuclear units, constructed from a {Re(CO)3(L1)}+ subunit linked to a {Re(CO)3Br2}- group through the sulfur donor of the pendant thioether arm. The series of complexes establishes that thiolate donors are effective ligands for the {M(CO)3}+ core and that a qualitative ordering of the coordination preferences of the core may be proposed: pyridyl nitrogen approximately thiolate > carboxylate > thioether sulfur > thiophene sulfur. The ligands L1 and L2 react cleanly with [99mTc(CO)3(H2O)3]+ in H2O/DMSO to give [99mTc(CO)3(L1)]+ (99m)Tc-1) and [99mTc(CO)3(L2)] (99mTc-2), respectively, in ca. 90% yield after HPLC purification. The Tc analogues 99mTc-1 and 99mTc-2 were subjected to ligand challenges by incubating each in the presence of 1000-fold excesses of both cysteine and histidine. The radiochromatograms showed greater than 95% recovery of the complexes.