Electrochemistry of rhenium(V) complexes with bidentate-bidentate and tridentate-bidentate schiff base ligands

The cathodic and anodic behaviour of rhenium(V) complexes, characterized by the ReO³⁺ core, with bidentate and tridentate Schiff base ligands, has been studied in acetonitrile solvent. Cyclic voltammetry and controlled potential coulometry were the main electroanalytical techniques employed to define the electrode processes. Electrolyses were also carried out with the aim to identify the nature of the reduced and oxidized products. In particular, it was possible to isolate and characterize new rhenium(VI) complexes, containing the group ReO⁴⁺, and the possibility of obtaining stable rhenium(IV) complexes has also been proved.     

Reentrant 2D Nanostructured Liquid Crystals by Competition between Molecular Packing and Conformation: Potential Design for Multistep Switching of Ionic Conductivity

Reentrant phenomena in soft matter and biosystems have attracted considerable attention because their properties are closely related to high functionality. Here, we report a combined experimental and computational study on the self-assembly and reentrant behavior of a single-component thermotropic smectic liquid crystal toward the realization of dynamically functional materials. We have designed and synthesized a mesogenic molecule consisting of an alicyclic trans,trans-bicyclohexyl mesogen and a polar cyclic carbonate group connected by a flexible tetra(oxyethylene) spacer. The molecule exhibits an unprecedented sequence of layered smectic phases, in the order: smectic A-smectic B-reentrant smectic A. Electron density profiles and large-scale molecular dynamics simulations indicate that competition between the stacking of bicyclohexyl mesogens and the conformational flexibility of tetra(oxyethylene) chains induces this unusual reentrant behavior. Ion-conductive reentrant liquid-crystalline materials have been developed, which undergo the multistep conductivity changes in response to temperature. The reentrant liquid crystals have potential as new mesogenic materials exhibiting switching functions.     

Oxygen permselective characteristics of a poly(vinylchloride)/liquid crystal/fluorocarbon ternary composite membrane

Poly(vinyl chloride) (PVC)/N-(4-ethoxybenzylidene)-4'-butylaniline (EBBA)/perfluorotributylamine (PFTA) ternary composite membrane was prepared and its oxygen permselectivity was investigated. In this membrane system, PFTA was contained in micelles formed by a surfactant of an ABA-type block copolymer (L44). The oxygen permeability coefficient, P_O2, for the PFTA-containing ternary composite membrane was greater than that for the PFTA-free binary one. The order of P_O2 for the ternary composite membrane was 10^?9 to 10^?8 cm³ (STP)-cm^?1-sec^?1-cmHg^?1, and the magnitude of the separation factor, P_O2/P_N2, about 3.5—4.0 in the temperature range of the nematic or isotropic state of EBBA. An increase in P_O2 caused by adding PFTA suggests that PFTA enhances the solubility of oxygen in the composite membrane surface. The ternary composite membrane showed a unique trend in its P_O2/P_N2—P_O2 relationship, that is, the magnitude of P_O2/P_N2 increased simultaneously with that of P_O2.