Oddvar Johansen

XANTHENE DYES AS SENSITIZERS FOR THE PHOTOREDUCTION OF WATER

Abstract— Some photochemical and photophysical properties of a group of xanthene dyes have been studied in relation to their roles as sensitizers for the photoreduction of water. New spectroscopic and kinetic measurements have been carried out with these dyes. The triplet states of the dyes undergo energy‐transfer and electron‐transfer, but with rate constants differing by two orders of magnitude in favour of the former pathway. The very efficient transfer of triplet energy from a group of dyes to an acceptor molecule led to the design of a greatly improved system for the photochemical production of hydrogen.

Highly efficient photoreduction of water using energy transfer

Abstract The photochemistry of the system water-tris(2,2′-bipyridine)ruthenium(II) dication—9-anthracenecarboxylate anion—methylviologen—ethylenediaminetetraacetic acid—platinum has been studied. Efficient triplet energy transfer from the excited ruthenium complex to the anthracene derivative leads to the formation of hydrogen in quantum yields up to 0.85.

The 9-anthracenecarboxylate anion as sensitizer for the photoreduction of water

Abstract Methylviologen quenches the excited singlet and triplet states of the 9-anthracenecarboxylate anion with high efficiency; only the triplet state produces a high yield of th methylviologen radical cation which can reduce water to hydrogen.

New inhibitors of auxin transport

3-Phenacylidinphthalid und dessen Hydrat verursachen einen konzentrationsabhängigen Verlust der geotropischen Reaktion der Wurzel und die Aufhebung der Apikaldominanz des Sprosses. Es wird nachgewiesen, dass die beiden Substanzen primär den basipetalen Transport des endogenen Auxins hemmen.