Electrochemistry of organometallic lyotropic chromonic liquid crystals

Application of periodic density functional theory calculations for exploring copper(II) coordination effects on the mesophase behavior of p-n-alkoxybenzoic acids

Copper(II) benzoates ([Formula: see text]OBA-Cu) with various terminal alkoxy carbon numbers, [Formula: see text]–12, were prepared from [Formula: see text]-[Formula: see text]-alkoxy benzoic acids (nOBAs). Fourier transform infrared (IR) experiments suggested that dimerization through copper(II) chelating bidentate coordination created [Formula: see text]OBA-Cu with a linear rod-like structure, similar to the hydrogen-bonded structure of its parent [Formula: see text]OBA. However, the coordination structure of [Formula: see text]OBA-Cu changed during heating. Periodic density functional theory calculations provided valuable insight into the possible arrangement of the parent and copper(II)-coordinated [Formula: see text]OBAs. The formation of binuclear complexes between two adjacent [Formula: see text]OBA-Cu dimers forced [Formula: see text]OBA-Cu to arrange itself in a layer and exhibit smectic A mesophase. Accordingly, four types of IR stretching absorption of benzoyl carbonyl were observed in binuclear [Formula: see text]OBA-Cu complexes, replacing the original symmetric and asymmetric vibrations of benzoyl carboxylate in chelating bidentate coordination. The lateral association by [Formula: see text]–[Formula: see text] interactions between adjacent parent [Formula: see text]OBA dimers preferred a progressive smectic C arrangement. The origin of the odd–even effect was understood from the consideration of the molecular structure.

Self-Assembly and Formation of Chromonic Liquid Crystals from the Dyes Quinaldine Red Acetate and Pyronin Y

The aqueous self-assembly behavior of the dyes Quinaldine red acetate and Pyronin Y in a wide range of concentrations is reported here for the first time. (1)H NMR spectroscopy, polarized-light optical microscopy, and small and wide X-ray scattering were used to get insight into molecular interactions, phase boundaries and aggregate structure. Quinaldine red acetate and Pyronin Y self-organize into unimolecular stacks driven by attractive aromatic interactions. At high concentrations, spatial correlation among the molecular stacks gives rise to nematic liquid crystals in both systems. Quinaldine red acetate additionally produces a rare chromonic O phase built of columnar aggregates with anisotropic cross-section ordered in a rectangular lattice. The O phase changes into a columnar lamellar structure as a result of a temperature-induced phase transition. Results open the possibility of finding chromonic liquid crystals in other commercially available dyes with a similar molecular structure. This would eventually expand the availability of these unique soft materials and thus introduce new applications for marketed dyes.

Phases and structures of sunset yellow and disodium cromoglycate mixtures in water

We study phases and structures of mixtures of two representative chromonic liquid crystal materials, sunset yellow FCF (SSY) and disodium cromoglycate (DSCG), in water. A variety of combinations of isotropic, nematic (N), and columnar (also called M) phases are observed depending on their concentrations, and a phase diagram is made. We find a tendency for DSCG-rich regions to show higher-order phases while SSY-rich regions show lower-order ones. We observe uniform mesophases only when one of the materials is sparse in the N phases. Their miscibility in M phases is so low that essentially complete phase separation occurs. X-ray scattering and spectroscopy studies confirm that SSY and DSCG molecules do not mix when they form chromonic aggregates and neither do their aggregates when they form M phases.

A model for efficient, semiconductor-free solar cells via supersensitized electron transfer cascades in photogalvanic devices

A mathematical model for a photosynthesis-inspired regenerative photogalvanic device, for transient rather than exclusively steady-state conditions, based on molecular electrochemistry rather than electron transfer processes involving semiconductors, is considered within this work and which is adapted from an experimental system previously developed (J. E. Halls and J. D. Wadhawan, Energy Environ. Sci., 2012, 5, 6541). Computational simulations suggest that pragmatically achievable systems behave as middle-of-the-range photo-rechargeable electrochemical capacitors for light-to-electrical energy storage; in contrast the system performance as a light-to-electrical energy convertor (viz., solar cell), for cells constructed from electrochemically reversible redox couples with fast photo-induced electron transfer reactions is critically dependent on the concentration of the supersensitiser; maximum power conversion efficiency of ca. 6.5% under 500 nm light, 2.4 mW cm(-2) intensity for typical experimental parameters, neglecting Ohmic losses, and employing galvanostatic discharge, with a power conversion efficiency that is capable of being increased by a factor of five (to ca. 34%) when the supersensitizer concentration increases by an order of magnitude (from 5.0 to 50.0 mM). Under an AM 2.0 solar spectrum, numerical simulations suggest that one potentially pragmatically achievable embodiment of this regenerative system is able to perform with a solar-to-electrical power conversion efficiency of 4.5% - an attractive realistic single cell value.