Ligand-based electronic effects on the electrocatalytic hydrogen production by thiosemicarbazone nickel complexes.

This work reports on the synthesis and characterization of a series of mononuclear thiosemicarbazone nickel complexes that display significant catalytic activity for hydrogen production in DMF using trifluoroacetic acid as the proton source. The ligand framework was chemically modified by varying the electron-donating abilities of the para substituents on the phenyl rings, which was expected to impact the capability of the resulting complexes to reduce protons into hydrogen. Over the four nickel complexes that were obtained, the one with the thiomethyl substituent, NiSCH3, was found to overtake the catalytic performances of the parent complex NiOCH3 featuring lower overpotential values and similar maximum turnover frequencies.

Efficient Light-Driven Hydrogen Evolution Using a Thiosemicarbazone-Nickel (II) Complex.

In the following work, we carried out a systematic study investigating the behavior of a thiosemicarbazone-nickel (II) complex () as a molecular catalyst for photo-induced hydrogen production. A comprehensive comparison regarding the combination of three different chromophores with this catalyst has been performed, using [ , and [ as photosensitizers. Thorough evaluation of the parameters affecting the hydrogen evolution experiments (i.

Electron transfer in a covalent dye-cobalt catalyst assembly - a transient absorption spectroelectrochemistry perspective.

Various oxidation states of the catalytically active cobalt center in a covalent dyad were electrochemically prepared and the light-induced excited-state processes were studied. Virtually identical deactivation processes are observed, irrespective of the oxidation state of the cobalt center, varying from Co to Co, indicating the absence of oxidative quenching within the dye-catalyst assembly.

A protocol for quantifying hydrogen evolution by dye-sensitized molecular photocathodes and its implementation for evaluating a new covalent architecture based on an optimized dye-catalyst dyad.

A protocol that combines gas chromatography and a high-sensitivity micro Clark-type electrode is described to quantify hydrogen production across gas and solution phases for systems operating at very low currents such as dye-sensitized H-evolving photocathodes. Data indicate that a significant fraction of H remains in aqueous solution even after several hours of experiments. Using this protocol, re-evaluation of a dye-sensitized H-evolving photocathode based on a dye-catalyst dyad showed a reproducible 66% increase of the faradaic efficiency compared with previously reported headspace GC measurements [Kaeffer et al.

Covalent Design for Dye-Sensitized H2-Evolving Photocathodes Based on a Cobalt Diimine-Dioxime Catalyst.

Dye-sensitized photoelectrochemical cells (DS-PECs) for water splitting hold promise for the large-scale storage of solar energy in the form of (solar) fuels, owing to the low cost and ease to process of their constitutive photoelectrode materials. The efficiency of such systems ultimately depends on our capacity to promote unidirectional light-driven electron transfer from the electrode substrate to a catalytic moiety. We report here on the first noble-metal free and covalent dye-catalyst assembly able to achieve photoelectrochemical visible light-driven H2 evolution in mildly acidic aqueous conditions when grafted onto p-type NiO electrode substrate.

Design and synthesis of novel organometallic dyes for NiO sensitization and photo-electrochemical applications.

Two metallo-organic dyes were synthesized and used for NiO sensitization in view of their photoelectrochemical applications. The new dyes present an original π-conjugated structure containing the [Ru(dppe)2] metal fragment with a highly delocalized allenylidene ligand on one side and a σ-alkynyl ligand bearing an electron-rich group, i.e.

Interactions of Isophorone Derivatives with DNA: Spectroscopic Studies.

Interactions of three new isophorone derivatives, Isoa Isob and Isoc with salmon testes DNA have been investigated using UV-Vis, fluorescence and circular dichroism spectroscopic methods. All the studied compounds interact with DNA through intercalative binding mode. The stoichiometry of the isophorone/DNA adducts was found to be 1:1.

Dye-sensitized PS-b-P2VP-templated nickel oxide films for photoelectrochemical applications.

Moving from homogeneous water-splitting photocatalytic systems to photoelectrochemical devices requires the preparation and evaluation of novel p-type transparent conductive photoelectrode substrates. We report here on the sensitization of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) diblock copolymer-templated NiO films with an organic push-pull dye. The potential of these new templated NiO film preparations for photoelectrochemical applications is compared with NiO material templated by F108 triblock copolymers.

Biocompatible photoresistant far-red emitting, fluorescent polymer probes, with near-infrared two-photon absorption, for living cell and zebrafish embryo imaging.

Exogenous probes with far-red or near-infrared (NIR) two-photon absorption and fluorescence emission are highly desirable for deep tissue imaging while limiting autofluorescence. However, molecular probes exhibiting such properties are often hydrophobic. As an attractive alternative, we synthesized water-soluble polymer probes carrying multiple far-red fluorophores and demonstrated here their potential for live cell and zebrafish embryo imaging.

New synthetic routes towards soluble and dissymmetric triphenodioxazine dyes designed for dye-sensitized solar cells.

New π-conjugated structures are constantly the subject of research in dyes and pigments industry and electronic organic field. In this context, the triphenodioxazine (TPDO) core has often been used as efficient photostable pigments and once integrated in air stable n-type organic field-effect transistor (OFET). However, little attention has been paid to the TPDO core as soluble materials for optoelectronic devices, possibly due to the harsh synthetic conditions and the insolubility of many compounds.

Red emitting neutral fluorescent glycoconjugates for membrane optical imaging.

A family of neutral fluorescent probes was developed, mimicking the overall structure of natural glycolipids in order to optimize their membrane affinity. Nonreducing commercially available di- or trisaccharidic structures were connected to a push-pull chromophore based on dicyanoisophorone electron-accepting group, which proved to fluoresce in the red region with a very large Stokes shift. This straightforward synthetic strategy brought structural variations to a series of probes, which were studied for their optical, biophysical, and biological properties.