A new role for the ‘pigments of life’
Scientists have just discovered how to reconfigure porphyrins — the "pigments of life" — which they have long had in their minds as potentially useful players in the fields of cancer therapy, solar energy, and materials science.
In nature, porphyrins are responsible for the green colour of leaves and the red colour of blood. All their functionality is based along the same core chemical structure: four smaller rings connected to one larger ring, with a little cavity in the centre. Most of their functions in nature (photosynthesis, oxygen transport) arise when they host different guest metals (magnesium, iron, cobalt, nickel) in the centre of the molecule. Different metals spark different functions in these 'metalloporphyrins'.
The discovery made by a five-strong research team was that by overcrowding the large porphyrin ring, they could force it to turn 'inside out' and change into the shape of a saddle. Importantly, this little trick enabled them to exploit the special properties of the formerly inaccessible core.
The team was led by Principal Investigator at the Trinity Biomedical Sciences Institute, and Chair of Organic Chemistry at Trinity College Dublin, Professor Mathias O. Senge. In close cooperation with Professor Stephen Connon, an expert in the field of organocatalysis, the scientists established standard reaction conditions and published their work in leading international journal Chemical Communications, which features the study on the front cover.
Professor Matthias O. Senge said: "By bending the porphyrin core out of plane, we hypothesised that we would be able to make use of the formerly buried functionalities by using the porphyrin as a catalyst."
"A catalyst is a compound that attracts other molecules and converts them into new entities and catalytic processes are at the heart of chemistry and nature, so they are of significant industrial and commercial interest. The discovery that these metalloporphyrins act as efficient metal-free catalysts now opens new horizons for these natural pigments."
"Soon, we hope to tailor porphyrins according to specific requirements and use our rational design approach for various applications in chemistry, biochemistry, physics and beyond."