Anton Launikonis

Colloidal platinum sols: preparation, characterization and stability towards salt

Stable aqueous colloidal platinum sols have been prepared by the citrate reduction of chloroplatinic acid. Particle size at the completion of the reaction was found to increase with increased heat input during reduction. The u.v.–visible spectrum of the platinum sols depends upon particle size up to 4 nm. A stirring–centrifugation procedure was used to identify the extent of coagulation induced by added electrolytes. It was found that the smaller platinum particles required higher concentrations of added electrolyte before being destabilized. A survey was made of the coagulation of the platinum sols induced by mono-, di- and tri-valent cations.Hydrogen treatment of platinum sols leads to growth of particles up to a maximum size of ca. 5 nm and substantial linkage of primary particles to form extensive aggregates. Such growth and aggregation lead to significant changes in the u.v.–visible spectra and reduced resistance to electrolyte-induced coagulation.

RAFT synthesis of linear and star-shaped light harvesting polymers using di- and hexafunctional ruthenium polypyridine reagents

The syntheses of linear and star-shaped light harvesting polymers with well defined structure and narrow molecular weight distribution are described. These polymers have ruthenium polybipyridine moieties as the energy trap cores and styrene functionalized coumarin monomers as the light absorbing antenna chromophores. The polymers have been made by reversible addition–fragmentation chain transfer (RAFT) polymerisation using di- or hexafunctional ruthenium-containing RAFT agents. The resulting ruthenium-containing polymers have narrow molecular weight distribution (polydispersity < 1.1) and exhibit energy transfer efficiencies of up to 60% between the coumarin donor dyes and the ruthenium acceptor chromophores.

PHOTOPRODUCTION OF HYDROGEN FROM LINKED CHROMOPHORES

Abstract On irradiation of solutions of anthryl‐substituted cobalt(III) cage complexes, [(l‐(anthryl‐9‐methylamino)‐8‐methyl‐3,6,10,13,16,19‐hexaazabicyclo [6.6.6] eicosane) cobalt(III)]3+ or [(l‐(4‐an‐thryl‐9)‐3‐aza‐butyl‐l‐amino)‐8‐methyl‐3,6,10,13,16,19‐hexaazabicyclo [6.6.6] eicosane)cobalt (III)]3* in the presence of ethylenediaminetetraacetic acid and platinum catalysts hydrogen was produced. These complexes act as coupled photosensitizers (anthracene moiety) and electron relays (cobalt cage) to produce H2via energy trapping and intramolecular electron transfer initially. The intensity of fluorescence and the photochemical reactivity favour the latter complex and the excited singlet state of the anthracene chromophore is invoked as the intermediate state leading to the reduction of Co(III) to Co(II).

2,7-Dimethylthieno[2,3-c : 5,4-c′]dipyridinium bisperchlorate as sensitizer for the photoreduction of water

The title compound fluoresces strongly and acts as both photosensitizer and electron relay for the photoreduction of water.