Structural consequences of oxidation of ferrocene derivatives : II. 1,1′,2,2′,4,4′-tris(trimethylene)ferrocenium perchlorate

The crystal and molecular structures of 1,1′,2,2′,4,4′-tris(trimethylene)ferrocenium perchlorate (I) were determined by X-ray crystallography. Despite the rigidity imparted to the molecule by the three non-adjacent bridges, the iron-to-ring distance of the cation was 4.4(4) pm longer than in the neutral compound, in agreement with what was reported for non-bridged ferrocene derivatives. The increased separation of the rings was accommodated by an increase in angle between the -carbon atoms and the ring-planes and by an increase in the ring-ring tilt angle.     

The kinetics of electron transfer in the thionine-coated electrode

Transient studies using potential jump and optical absorbance have been carried out on thionine-coated electrodes. Both types of transient are shown to fit a simple diffusion model. At pH 1.3 the characteristic diffusion time varies with the size of the anion present in the electrolyte, showing that diffusion of the counter ions is the rate-limiting process. At pH 5 faster, more uniform, rates are found which are attributed to rate-limiting electron hopping. The rate constant for this process is in rough agreement with the rate of the conproportionation reaction of thionine and leucothionine. The electron-hopping process also limits the maximum current that can be passed through the modified electrode in the steady state.     

On the Reflexivity of Cappell-Shaneson 2-Knots

We show that up to change of orientation there is only one Cappell-Shaneson2-knot which is determined by its exterior.     

The algebraic characterization of the exteriors of certain 2-knots

Summary We study 2-knots with virtually solvable group by applying recent work of Freedman to the 4-manifolds obtained by surgery on such knots. In particular we show that Gluck reconstruction is the only ambiguity in recovering the Cappell-Shaneson knots (as TOP locally flat knots) from their groups alone.     

A combined electrochemical quartz-crystal microbalance probe beam deflection (EQCM-PBD) study of solvent and ion transfers at a poly

The oxidative polymerisation of the complex2,3-dimethyl-N,N'-bis-(salicylidene)butane-2,3-diaminatonick-el(II), [Ni(saltMe)], was monitored by the electrochemical quartz microbalance (EQCM) and crystal impedance techniques. Polymerisation efficiency was maintained throughout deposition of a film, which behaved rigidly, on the electrode. A combined EQCM-PBD (probe beam deflection) study of the redox process of the film exposed to a monomer-free solution of 0.1 M tetraethylammonium perchlorate (TEAP) in acetonitrile showed an electroneutrality mechanism dominated by anion movement accompanied by co-transfer of solvent above 0.8 V. The individual contributions of all the mobile species involved in the redox switching of the poly[Ni(saltMe)] film were determined quantitatively by temporal convolution analysis; the estimated solution-phase diffusion coefficient of the exchanged species was 1.24 x 10(-5) cm2s-1.     

Improved selectivity of chemical colour reactions by simple gas chromatographic separation

Gas chromatography is applied to improve the selectivity of sensitive organic colour tests without the use of complicated apparatus.     

On 4-manifolds homotopy equivalent to circle bundles over 3-manifolds

We give criteria for a closed 4-manifold to be homotopy equivalent to the total space of an S¹-bundle over a closed 3-manifold. In the aspherical case the conditions are that the Euler characteristic be 0 and that the fundamental group have an infinite cyclic normal subgroup such that the quotient group has one end and finite cohomological dimension. Under further assumptions on this quotient group we characterize the total spaces of such bundles over -or H² × E¹-manifolds and over E³-, Nil³- or Sol³-manifolds up to s-cobordism and homeomorphism respectively.     

Dynamic quartz crystal impedance measurements of polyvinylferrocene film deposition

Dynamic crystal impedance measurements were used to study the electrochemically-driven deposition of polyvinylferrocene (PVF) films from dichloromethane solutions of PVF onto Au electrodes of a quartz crystal microbalance. Under all the conditions studied, the PVF films were non-rigid, to an extent that depended upon several experimental factors. Films deposited from solutions containing perchlorate salts of tetraalkylammonium salts departed less from rigidity than those deposited under otherwise identical conditions from tetrafluoroborate media. In contrast, the use of different tetraalkylammonium cations, or the use of a potential sweep vs. a potential step from 0 V to the deposition potential (0.7 V), made no significant difference. The departure from rigid characteristics varied with coverage. For the interval of time during deposition that the coverage was 10–160 nmol cm⁻² (of monomeric ferrocene units), the films showed no additional departure from rigidity. On the basis that the upper figure corresponds closely to a “monolayer” of terminally attached chains of mean length, we attribute this behaviour to the presence of a dense film, within which chain motion is considerably restrained.