A series of dimeric metalloporphyrin molecules has been synthesized in which the two porphyrin rings are constrained to lie parallel to one another by two amide bridges of varying length that link the rings together. These cofacial metalloporphyrins have been applied to the surface of graphite electrodes and tested for catalytic activity toward the electroreduction of dioxygen to water in aqueous acidic electrolytes. All molecules tested exhibited some catalytic activity, but hydrogen peroxide rather than water was the chief reduction product. However, the dicobalt cofacial porphyrin linked by four-atom bridges produced a catalyzed reduction almost exclusively to water and at exceptionally positive potentials. Rotating ring-disk voltammetric measurements were employed to diagnose the electrode reaction pathway and a possible mechanism for the observed catalysis is suggested. The results seem to demonstrate the participation of two metal centers in controlling the course of a multiple-electron process.

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Ausgehend von den Monopyrrolen (I) und (II) werden über intermediäre Dipyrromethene die Porphyrine (III) aufgebaut.

In 1998, Toyo Gosei Co. published a paper on the development of a new water-soluble photopolymer of high sensitivity, PVA-ARBB. In close co-operation with LG. Philips Displays, the new material was further developed to be applicable in patterning the phosphor layer of a CRT screen. The new material shows about 3 times higher light sensitivity, gives 4-5% higher luminance, has no dark reaction, and is chromium-free. It is the first chromium-free photoresist used for phosphor patterning in CRT mass production. A comparison is presented between the conventional resist and the new resist. A survey is given of the most important process conditions.

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