Self-assembled molecular rafts at liquid|liquid interfaces for four-electron oxygen reduction

Abstract

The self-assembly of the oppositely charged water-soluble porphyrins, cobalt tetramethylpyridinium porphyrin (CoTMPyP 4+) and cobalt tetrasulphonatophenyl porphyrin (CoTPPS 4-), at the interface with an organic solvent to form molecular "rafts", provides an excellent catalyst to perform the interfacial four-electron reduction of oxygen by lipophilic electron donors such as tetrathiafulvalene (TTF). The catalytic activity and selectivity of the self-assembled catalyst toward the four-electron pathway was found to be as good as that of the Pacman type cofacial cobalt porphyrins. The assembly has been characterized by UV-visible spectroscopy, Surface Second Harmonic Generation, and Scanning Electron Microscopy. Density functional theory calculations confirm the possibility of formation of the catalytic CoTMPyP 4+/ CoTPPS 4- complex and its capability to bind oxygen. © 2011 American Chemical Society.