Precise synthesis of porphyrin array scaffolding polyisocyanides

Aryl isocyanides bearing free‐base and metallo‐porphyrins were prepared and polymerized with a Pd–Pt μ‐ethynediyl complex as the initiator to give polymers with narrow polydispersity indices. The molecular weights of the resulting polymers were precisely controlled by the initial feed ratio of the porphyrin monomer to the initiator. The UV–VIS spectra suggested that the porphyrin pendants are regularly arranged to form stacked columns. Metallo‐porphyrin polymers were also prepared by reacting free‐base porphyrin polymers with metal salts. The successive reactions of free‐base and zinc‐porphyrin monomers resulted in the formation of diblock polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 585–595, 2006     

Über die Konzentrationsabhängigkeit der Viskosität bei organischen Hochpolymeren

Zusammenfassung Es wird eine Korrekturformel zur 8. Potenzformel von Philippoff-Heß vorgeschlagen, die auch die Fälle gut wiedergibt, wo die einfache 8. Potenzformel ebenso wie andere Viskositätsgleichungen bisher versagten. Im einzelnen wird die Gleichung geprüft an folgenden bisherigen Ausnahmen: Cellit in Eisessig (Philippoff-Heß), polymere-Hydroxydekansäuren in sym-Tetrachloräthan(Kraemer-von Natta), polymere Polystyrole in Benzol (Dane). In jedem Falle stellen diek-Werte gute Konstanten dar.Die charakteristische Viskositätskonstantek zeigt eine lineare Zunahme mit dem Molekulargewicht der Polymerhomologen.Die Temperaturabhängigkeit vonk unda wird geprüft.     

Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate

An overoxidized polypyrrole colloid, which can recognise enantiomers of amino acids has been prepared by a newly developed molecular imprinting technique. A polypyrrole colloid, which had been polymerised from a mixture of pyrrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and L-lactate (dopant), was overoxidized to create a dopant-complementary cavity. The enantioselectivity of the overoxidized colloid was evaluated by comparing the uptake of L-alanine and L-cysteine with that of the respective D-enantiomers. The L/D uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantiomers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by L-lactate. In contrast, a colloid templated with L-phenyllactate took up L-phenylalanine with a higher enantioselectivity of about 7. A colloid templated with L-lactate was applied to surface chirality analysis through enantioselective adsorption on cysteine-modified gold surfaces. Quartz microbalance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surface modified with L-cysteine than to one modified with D-cysteine.     

Diffusion coefficient of 36Cl in silver chloride

Diffusion coefficient of 36Cl in silver chloride was revealed to be about 1 x 10(-10)-4 x 10(-11) cm2 . s-1 in the range of 400 degrees C-200 degrees C by means of radioactive tracer measurements. Activation energy for diffusion was calculated about 0.13 eV. These results were different from those obtained by Maurer and Compton.     

Supported molybdena catalysts: Characterization of oxidized,reduced, and sulfided MoO3 prepared by an adsorption method

Highly dispersed molybdena-titania catalyst can be prepared by an equilibrium adsorption method. In this method, molybdate anions adsorb onto the positively charged titania surfaces via electrostatic attraction by controlling the pH of the impregnating solution and they increase as an inverse function of the pH. ⁹⁵Mo-NMR and UV spectroscopic studies of impregnating solution show that the polymeric species like Mo₇O₂₄ ⁶-ions are adsorbed on titania in the acidic impregnating solution. XRD, Raman, and XPS data of the calcined samples show that mono-layer coverage of molybdenum oxide over-layer possesses a highly distorted MoO₆ group with a molecular geometry resembling the distorted square pyramid. The catalytic oxidation of methanol over the surface molybdate species on titania possesses higher turnover numbers and higher selectivities of partial oxidation products than the catalysts supported on alumina, silica, zirconia, or magnesia. Changes of the surface properties either after reduction and sulfiding treatment over monolayer catalyst on titania have also been investigated. The NO chemisorption and XPS studies show that two types of active sites appeared after reduction treatment: one site is active for hydrogenation of 1,3-butadiene and the other site is active for metathesis of propene. A higher degree coordinative unsaturations of MO is required for hydrogenation than metathesis. After sulfiding treatments of the catalyst, hydrogenation of 1,3-butadiene also requires triply coordinative unsaturation, and hydrogenolysis of thiophene requires the ensemble of doubly or triply coordinative unsaturations.     

Preparation,stability, reactivity and synthetic utility of a cadmium stabilized complex of difluoromethylene phosphonic acid ester

Diethyl bromodifluoromethyl phosphonate reacts readily with cadmium metal to form a stable cadmium complex. Depending on solvent, this functionalized organocadmium reagent exhibits stability for days to months. It reacts with a variety of electrophiles and serves as a synthetically useful source for the introduction of the difluoromethylene phosphonate group into organic compounds.The synthetic utility of a wide variety of fluoromethylene phosphonium ylides has been a major effort in our laboratory over the past several years [1]. The generation and capture of difluoromethylene ylides ($\text{1}$) as a general route to difluoromethylene olefins has been of especial interest to us [2]. In an effort to increase the nucleophilicity of the ylide, we have attempted to prepare the analogous phosphonate ylide ($\text{2}$). Although we have achieved modest success [3] by $\text{insitu}$ capture of ($\text{2}$) in the reaction of

sodium dialkyl phosphites with diethyl bromodifluoromethylphosphonate ($\text{3}$), attempts to pregenerate ($\text{2}$), either from diethyl difluoromethylphosphonate ($\text{4}$) or ($\text{3}$), have met with little success. ($\text{2}$) appears to have minimal stability even at low temperatures, and scale up processes of synthetic value would seem to be difficult.     

Characterization of modified alumina as adsorbents. Modification of alumina with alkali metal phosphates

Summary Alumina may be considerably modified by impregnating at 100°C in the alkali metal phosphate solution. The available solution for modification was the KOH–K₂HPO₄–AlPO₄ (11.51M) solution or the NaOH–Na₂ HPO₄ (0.81.1 M or 11.5M) solution. The appreciable improvement on chromatograms was obtained by preheating of the alumina, especially above 800°C prior to impregnating A further modification may be made by ignition of the alumina impregnated. The x-ray diffraction studies revealed the phase transformation of the alumina inducing the modification, and the essential factor of the present modification method being the thermal treatment of the alumina at temperatures forming -alumina.     

Syntheses and structures of mono-, di- and tetranuclear rhodium or iridium complexes of thiacalix[4]arene derivatives

The reactions of [Cp*MCl2]2(Cp*=eta5-C5Me5, M = Rh, Ir) with thiacalix[4]arene (TC4A(OH)4) and tetramercaptothiacalix[4]arene (TC4A(SH)4) gave the mononuclear complexes [(Cp*M){eta3-TC4A(OH)2(O)2}] and the dinuclear complexes [(Cp*M)2{eta3eta3-TC4A(S)4}] respectively, while the analogous reactions with dimercaptothiacalix[4]arene (TC4A(OH)2(SH)2) produced the tetranuclear complexes [(Cp*M)2(Cp*MCl2)2-{eta3eta3eta1eta1-TC4A(O)2(S)2}].     

Cross-coupling of alkenyl,aryl or allylic selenides and grignard reagents catalyzed by nickel-phosphine complexes

Alkenyl, aryl or allylic selenides smoothly couple with Grignard reagents in the presence of Ni(II)-phosphine complexes as catalysts to afford the corresponding unsaturated compounds in good yields. The reactivity order of coupling reaction with BuMgBr catalyzed by NiCl₂ [Ph₂PCH₂CH₂CH₂PPh₂] was found to be PhSeMe « PhCl > PhSMe by the competitive reactions.