New Twist on the Light-Switch Effect: Controlling the Fate of Excited States with pH in a 4-Hydroxy-thiazol-extended Ruthenium(II) Dppz Complex.

We present a pH-dependent study of the excited state dynamics of a novel Ru complex bearing a 4-hydroxy thiazol-substituted dppz (dipyridophenazine) ligand () and its deprotonated form (). We combine steady-state and time-resolved absorption and emission spectroscopy with electrochemical investigations to characterize the excited state relaxation, which upon photoexcitation at 400 nm is determined by a multitude of initially populated MLCT states for both complexes. Subsequently, for , two long-lived excited states are populated, leading to dual emission from the complexes, a feature that vanishes upon deprotonation.

Ligand-Structure Effects on -Heterocyclic Carbene Rhenium Photo- and Electrocatalysts of CO Reduction.

Three novel rhenium -heterocyclic carbene complexes, [Re]-NHC-1-3 ([Re] = -Re(CO)Br), were synthesized and characterized using a range of spectroscopic techniques. Photophysical, electrochemical and spectroelectrochemical studies were carried out to probe the properties of these organometallic compounds. Re-NHC-1 and Re-NHC-2 bear a phenanthrene backbone on an imidazole (NHC) ring, coordinating to Re by both the carbene C and a pyridyl group attached to one of the imidazole nitrogen atoms.

Ruthenium Assemblies for CO Reduction and H Generation: Time Resolved Infrared Spectroscopy, Spectroelectrochemistry and a Photocatalysis Study in Solution and on NiO.

Two novel supramolecular complexes ([Ru(dceb)(bpt)Re(CO)Cl](PF)) and ([Ru(dceb)(bpt)PtI(HO)](PF)) [dceb = diethyl(2,2'-bipyridine)-4,4'-dicarboxylate, bpt = 3,5-di(pyridine-2-yl)-1,2,4-triazolate] were synthesized as new catalysts for photocatalytic CO reduction and H evolution, respectively. The influence of the catalytic metal for successful catalysis in solution and on a NiO semiconductor was examined. IR-active handles in the form of carbonyl groups on the peripheral ligand on the photosensitiser were used to study the excited states populated, as well as the one-electron reduced intermediate species using infrared and UV-Vis spectroelectrochemistry, and time resolved infrared spectroscopy.

Photophysics of Ruthenium(II) Complexes with Thiazole π-Extended Dipyridophenazine Ligands.

Transition-metal-based donor-acceptor systems can produce long-lived excited charge-transfer states by visible-light irradiation. The novel ruthenium(II) polypyridyl type complexes and based on the dipyridophenazine ligand () directly linked to 4-hydroxythiazoles of different donor strengths were synthesized and photophysically characterized. The excited-state dynamics were investigated by femtosecond-to-nanosecond transient absorption and nanosecond emission spectroscopy complemented by time-dependent density functional theory calculations.

Preparation of saline-stable, silica-coated triangular silver nanoplates of use for optical sensing.

Triangular silver nanoplates (TSNPs) may find application in next generation optical bio-sensors owing to the high sensitivity of the spectral position of their main plasmon band to changes in local refractive index. Unfortunately, etching of the anisotropic nanoplates to spherical particles occurs upon exposure to chloride ions from salt, with a concomitant decrease in optical sensitivity. Herein are detailed two general methods for the silica coating of TSNPs, with the aim of forming a protective barrier against chloride etching.

Redox and electrochemical water splitting catalytic properties of hydrated metal oxide modified electrodes.

This paper presents a review of the redox and electrocatalytic properties of transition metal oxide electrodes, paying particular attention to the oxygen evolution reaction. Metal oxide materials may be prepared using a variety of methods, resulting in a diverse range of redox and electrocatalytic properties. Here we describe the most common synthetic routes and the important factors relevant to their preparation.

Enhancing the activity and tuning the mechanism of formic acid oxidation at tetrahexahedral Pt nanocrystals by Au decoration.

Tetrahexahedral Pt nanocrystals (THH Pt NCs), bound by high index facets, belong to an emerging class of nanomaterials that promise to bridge the gap between model and practical electrocatalysts. The atomically stepped surfaces of THH Pt NCs are extremely active for the electrooxidation of small organic molecules but they also readily accommodate the dissociative chemisorption of such species, resulting in poisoning by strongly adsorbed CO. Formic acid oxidation is an ideal reaction for studying the balance between these competing catalyst characteristics, since it can proceed by either a direct or a CO mediated pathway.

Redox switching and oxygen evolution at oxidized metal and metal oxide electrodes: iron in base.

Outstanding issues regarding the film formation, redox switching characteristics and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been revisited. The oxide is grown using a repetitive potential multicycling technique, and the mechanism of the latter hydrous oxide formation process has been discussed. A duplex layer model of the oxide/solution interphase region is proposed.

Redox switching and oxygen evolution electrocatalysis in polymeric iron oxyhydroxide films.

Outstanding issues regarding the redox switching characteristics and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been examined. Charge percolation through the hydrous layer has been quantified, using cyclic voltammetry, in terms of a charge transport diffusion coefficient D(CT) which admits a value of ca. 3 x 10(-10) cm2 s(-1).