A Prebiotic Surface Catalyzed Photochemically Activated Synthesis of Corrin Derivatives: A and B Monomers

Abstract: Alkynes such as but-2-ynimine, propyne and ethyne form weak charge-transfer, ?^2 -alkynyl complexes, with surface catalysts such as Mg.porphin in which the alkynyl group is positively charged and the porphin has a negative charge. The enthalpy changes are -0.040, -0.002 and -0.018 h, respectively. However, if the adduct is excited to a higher energy state it may migrate to form a weak charge transfer bond with the nitrogen atom of an adjacent pyrrole unit. If the catalyst, Mg.porphin accepts two adducts they may have opposite charges. The di-adduct complexes may bond leading to high energy products in which the orientation is determined by the exciting radiation. Subsequent reactions with nucleophiles such as cyanoacetylene and methyl cyanide anions may give derivatives of pyrroline that can oligomerize to tetramers that can cyclise to corrin derivatives. The reactions have been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2 /6-31G* level.