A family of [Pt(II)(diimine)(dithiolate)] complexes of general formula [Pt{X,X'(CO(2)R)(2)-2,2'-bipyridyl}(maleonitriledithiolate)] (where X = 3, 4, or 5 and R = H or Et) have been synthesized, spectroscopically and electrochemically characterized, and attached to a TiO(2) substrate to be tested as solar cell sensitizers. A single-crystal X-ray structure showing a large torsion angle between the bipyridyl rings was determined for [Pt{3,3'(CO(2)Et)(2)-2,2'-bipyridyl}(maleonitriledithiolate)].MeCN. The effect of changing the position of the bipyridyl substituents from 3,3' to 4,4' and 5,5' is discussed with reference to structural and electronic changes seen within the different members of the family of molecules. The first UV/vis/NIR spectroelectrochemical study of complexes of this general formula is discussed. All three complexes (where R = H) were tested as solar cell sensitizers, with the 3,3'-disubstituted bipyridyl complex giving an intermediate dye loading value but superior photovoltaic performance to those of the other two. The performance of this sensitizer is then compared with that of a well-known Ru polypyridyl sensitizer, the ditetrabutylammonium salt of [RuL(2)(NCS)(2)] (L = 2,2'-bipyridyl-4,4'-dicarboxylato), commonly called N719.

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Biological vectors are important for redistribution of nutrients in many ecological systems. While availability of iron (Fe) to phytoplankton limits pelagic productivity in the Southern Ocean, biomagnification within marine food webs can lead to high concentrations of Fe in the diet of seabirds and marine mammals. We investigated patterns in concentrations of the micronutrients Fe, Co, Zn and Mn, and the toxins Cd and As, in the guano of oceanic, coastal and predatory seabirds and in faeces of 2 species of marine mammals that congregate to breed in the sub-Antarctic Auckland Islands. We found that much of the variability in concentrations of Fe, Co, Zn and Mn among species could be explained by foraging behaviour and by trophic position. We observed concentrations of Fe to be 8 orders of magnitude higher in the guano of predators and coastal foragers than in the sub-Antarctic mixed layer. High concentrations of As and Cd were associated with organic matter sources from macroalgae. Analyses of the molar ratio Fe:Al indicated that Fe within food webs supporting seabirds has likely been extensively recycled from its lithogenic source. Patterns in Fe:N among species indicated that Fe is concentrated 2 to 4 orders of magnitude in the guano of seabirds compared to limiting conditions for phytoplankton growth in sub-Antarctic waters. These data highlight the potential role of seabirds and marine mammals in the redistribution of micronutrients in the Southern Ocean and their likely role as key nutrient vectors in the ecosystem, particularly around the sub-Antarctic islands during the breeding season.Seabirds such as the albatross Diomedea epomophora are important nutrient vectors in the Southern Ocean.

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