Switchable electrical conductivity in a three-dimensional metal–organic framework via reversible ligand n-doping

Redox-active metal–organic frameworks (MOFs) are promising materials for a number of next-generation technologies, and recent work has shown that redox manipulation can dramatically enhance electrical conductivity in MOFs. However, ligand-based strategies for controlling conductivity remain under-developed, particularly those that make use of reversible redox processes. Here we report the first use of ligand n-doping to engender electrical conductivity in a porous 3D MOF, leading to tunable conductivity values that span over six orders of magnitude. Moreover, this work represents the first example of redox switching leading to reversible conductivity changes in a 3D MOF.

Redox-active ligands are used to reversibly tune electrical conductivity in a porous 3D metal–organic framework (MOF).     

Kinetics of vesicle formation

 The kinetics of vesicle formation from a hydrotrope (sodium xylenesulfonate) solution of a surfactant (Laureth 4) is studied by the use of a stopped-flow apparatus combined with a dynamic light scattering device to determine vesicle size in the system. The hydrotrope system studied presents a system with a high surfactant solubilization combined with vesicle formation simply by dilution with water. The kinetic results show a single exponential decay time. The kinetic analysis indicates that the vesicles are formed from a molecular solution which resulted from the shear in the stopped-flow device and grow by monomeric association. Received: 1 October 1996 Accepted: 22 November 1996     

Chemical recovery of thallium-203 following production and separation of lead-201

Because of the cost and limited availability of isotopically enriched thallium (>92%²⁰³Tl), its use in the²⁰³Tl(p, 3n)²⁰¹Pb nuclear reaction necessitates chemical recovery. An adaptive method has been developed and evaluated. After the separation of²⁰¹Pb, the²⁰³Tl(I) is oxidized to²⁰³Tl(III) by Cl₂, Br₂ or [Fe(CN)₆]⁻², precipitated as Tl(OH)₃ with NaOH and subsequently converted to Tl₂O₃ by heating. Due to potential loss during recovery, the solubilities of Tl(OH)₃ and Tl₂O₃ in aqueous solution as a function of pH have been studied using the internal tracer²⁰²Tl (T=12.2d), produced during cyclotron irradiation. Effective solubility product constants have been determined to be 5.4·10⁻⁴⁸ and 2.5·10⁻⁴⁷ for Tl(OH)₃ and Tl₂O₃, respectively.     

The determination of selenium(IV) by thermometric enthalpy titration with thiosulphate

Selenimn(IV) can be titrated in the range 0.2–6 mg with thiosulphate; relative standard deviations are 1.2–0.54%. Experimental conditions were manipulated to use the endothermic enthalpy of dilution and disproportionation of thiosulphate to advantage in improving end-point precision. Common anions do not interfere; interferences from copper(II), iron(III), lead(II) and mercury(II) can be minimized by masking.     

Collision induced fragmentation of mass-selected (CO2) n + clusters

The collisional velocity dependence of the cross sections for fragmentation of mass-selected (CO₂) _n ⁺ (n+2...7) clusters in collisions with Ar atoms is presented. Interesting structure can be observed in the cross sections which indicate that the collision occurs between the Ar atom and one CO₂ molecule within the cluster. The results may be explained by assuming that the collision leads to either vibrational excitation of a loosely bound CO₂ monomer which then leaves the cluster or excitation of the entire cluster to a dissociative state.     

Raman spectroscopy in liquids at high pressure

The pressure dependence of the reorientational correlation function for chloroform has been measured by analysis of the Raman 3019 cm^{? 1} A₁ CH stretching lineshape at 1, 1000, and 2000 bar and 23°C. These reorientational correlation functions were obtained using the method of spectral Fourier deconvolution introduced by Bratos. The results are compared to the correlation times obtained from the NMR deuteron T₁ relaxation times for CDCl₃ and those calculated from high pressure viscosity measurements.     

Synthesis of (-)-calicoferol B

The first total synthesis of (-)-calicoferol B (III) is described. The cyclozirconation product I, prepared in enantiomerically pure form, was converted into the CD ring chiron II. This was coupled with the aromatic A-ring, and then the side chain was constructed with control of relative and absolute configuration to complete the total synthesis of III. The first total synthesis of (-)-calicoferol B (1) is described. The cyclozirconation product 8, prepared in enantiomerically pure form, was converted into the CD ring chiron 6. This was coupled with the aromatic A-ring, and then the side chain was constructed with control of relative and absolute configuration to complete the total synthesis of 1.     

On the ring of invariants ofF_{2^n }^*

In [1] the first and last authors studied a decomposition ofH ^*(R P ^∞×…×R P ^∞;F ₂) into modules over the Steenrod algebra obtained from an action of the cyclic group . Here a minimal set of generators for the ring of invariants is characterized and counted by analyzing the associated ring of Laurent polynomials. A structure theorem for the ring of invariant Laurent polynomials is given and a ‘destabilisation cancels localisation’ theorem is obtained. The authors gratefully acknowledge the support of NSERC. 1980 Mathematics Subject classification, 13F20, 55. Keywords: Invariant theory, Steenrod algebra.