Metalloporphyrins in Prebiotic Photocatalysis and Bioenergetics

Abstract

Metalloporphyrins are widespread in the bioenergetics of extant biology and are plausible candidates for similar roles during the origins of life. Sunlight is the source of energy for the vast majority of the extant biosphere and could have driven reactions of interest to origins of life. However, selectivity in such reactions requires catalytic intervention. Towards this, we investigate the plausible role the porphyrin macrocycles and corresponding metalloporphyrins could have played as photocatalysts in the origins of life. We compare the photocatalytic performance of the different metalloporphyrins through various model reactions and try to rationalise the selection of the Mg2+-complex in extant biology. It is observed that only a subset among the porphyrin macrocycle and the metalloporphyrins are photocatalytically viable. Mechanistic investigations point towards the role of stable excited states in enabling photocatalytic properties. This sets the stage towards studying reactions of very direct relevance to prebiotic chemistry, in order to understand the kind of processes that could have been photocatalytically driven on the prebiotic earth.