Mössbauer and infrared spectroscopic studies of novel mixed valence states in cobaltous ferrocyanides and ferricyanides

Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co⁺²Fe^II) and ferricyanides (Co⁺²Fe^III) in an ozone flow. The CN stretching bands occur at 2085 cm^–1 for Co⁺²Fe^II and at 2160 cm^–1 for Co⁺²Fe^III. After the ozonization process of Co⁺²Fe^II, an intense band approximately at 2125 cm^–1 is detected. This intermediate band must correspond to a mixed valence state of the type: Fe^II–CN–Co²⁺–NC–Fe^III Mössbauer spectra recorded in situ during the ozonization of Co⁺²Fe^II show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co⁺²Fe^II after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable.     

Temperature dependence of the viscosity of dilute poly(β-naphthyl methacrylate) solutions

The temperature dependence of the actual viscosity of dilute poly(β-naphthyl methacrylate) solutions was described by an Arrhenius expression according to Moore's treatment. The apparent activation energy of flow was found to be lower for solutions in benzene, toluene and tetralin than for solvent. In dioxane, a good solvent, the activation energy was nearly constant and close to that for the solvent. The pre-exponential terms were, in all cases, higher for solutions than for the solvents. The decrease in activation energy and increase in pre-exponential term are largely dependent on solvent power: the maximum effect is found in the poorest solvent. This behaviour is discussed in connection with the temperature dependence of the Mark-Houwink and of the Fox-Flory constants obtained from intrinsic viscosity data: the differences in the activation energy of flow and in the pre-exponential term between the solvent and the solutions are related to variation of coil expansion with temperature.     

Rigidified calixarenes bearing four carbamoylmethylphosphineoxide or carbamoylmethylphosphoryl functions at the wide rim

Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4c with the CMPO-active ester 5b gave the tetraphosphine oxide 6a, while the tetraphosphinate 6b and the tetraphosphonate 6c were obtained by Arbuzov reaction of tetrabromoacetamido derivative 7 with PhP(OEt)2 or P(OEt)3. The extraction ability of these CMPO derivatives was checked for selected lanthanides and actinides and compared with the analogous compounds 1b, 10b and 10d derived from calix[4]arene tetrapentyl ether. All rigidified bis(crown ether) ligands are more effective extractants than their pentyl ether counterparts and require only 1/10 of the concentration (cL= 10 4M) to obtain the same distribution coefficients, while with CMPO itself a 2,000-fold concentration is necessary. This could be a consequence of a better preorganisation of the ligating functions owing to the rigidity which on the other hand did not change the observed selectivity for americium (DAm/DEu=9-19) and for light lanthanides over heavy ones. NMR relaxivity titration curves show that the complex of Gd3+ with ligand 6a is highly oligomerised in anhydrous acetonitrile over a large range of ligand:metal concentration ratios. Nuclear magnetic relaxation dispersion (NMRD) profiles also showed that large oligomers were formed, and their mean tumbling times were deduced from the Solomon-Bloembergen-Morgan equations. The NMR spectra of dia- and paramagnetic lanthanide complexes with 6a agreed with the presence of two conformers with an elongated calix[4]arene skeleton in which the distances between opposite methylene groups are different. Contrary to what was observed with ligand 2a, the addition of nitrate ions does not labilize the metal complexes, presumably because of the rigidification effect of the ether bridges. Single-crystal X-ray structures were obtained for the active ester 5b and for diphenylphosphorylacetic acid 5a.     

Electro-optical studies on synthetic polyelectrolytes—III: Electric birefringence of poly-n-alkyl-4-vinylpyridinium bromides in various solvents

The field strength dependences of the electric birefrigence of poly-N-butyl-4-vinylpyridinium (4-PVP · BuBr) samples have been measured in water and in various organic polar solvents. The observed change of sign of the birefringence, negative in water and positive in nitromethane, is explained by considering the respective influences of the intrinsic and form optical anisotropies. The lower degree of extension of the polyelectrolyte in some organic solvents is attributed to a lower degree of dissociation of the ionic sites. The influence of the dielectric constant and of the functional character of the solvent on the dissociation and solvation processes of the ionic sites is taken into account. Relaxation measurements in dimethylsulphoxide as a function of the molecular weight allow quantitative expression of the degrees of extension and of rigidity of the polyelectrolyte; the presence of aggregates has also been detected in DMSO solutions. A long alkyl chain, such as octyl, attached to the quaternary pyridinium groups strongly modifies the conformation of the polyelectrolyte and a polyelectrolyte-polysoap transition has been observed as a function of the solvent composition in water-ethanol mixtures.     

Search for color singlet technicolor particles in p&pmacr; collisions at radicals = 1.8 TeV

We search for color singlet technirho and technipion production in p&pmacr; collisions at sqrt[s] = 1.8 TeV recorded with the Collider Detector at Fermilab. These exotic technimesons are present in a model of walking technicolor. The signatures studied are lepton plus two jets plus E(T) and multijet final states. No excess of events is seen in either final state. We set an upper limit on the technirho production cross section and exclude a region in the technipion mass versus technirho mass plane.