Enhanced O2 electrocatalysis by a highly conjugated cobalt(II) porphyrin

Cobalt(II) tetraphenyltetranaphthoporphyrin, with extended conjugation at the pyrrole units, has been synthesized and its spectroscopic and electrocatalytic behavior toward the reduction of oxygen has been investigated. The new complex shows a red shift for the Soret band of 75 nm compared to its cobalt(II) tetraphenylporphyrin analog. In addition, the new complex shows enhanced electrocatalytic ability for the reduction of oxygen in acidic media converting over 50% of the oxygen directly to water, a four electron process at relatively high potentials.

Cobalt(II) inserted into a highly conjugated porphyrin macrocycle displays red-shifted electronic transitions and an enhanced electrocatalytic ability toward the reduction of oxygen in acidic media when compared to its less conjugated analog cobalt(II) tetraphenylporphyrin.Figure optionsDownload as PowerPoint slideHighlights
► A new cobalt(II) porphyrin with extended p-conjugation has been synthesized.
► The new metal complex and its free-base porphyrin have red-shifted electronic spectra.
► New cobalt complex shows enhanced electrocatalysis of oxygen in acidic solutions.