Conformation and electron-transfer chemistry in model photosynthetic reaction centres determined by fast atom bombardment mass spectrometry

Abstract

Fragment ions, derived from a series of capped and dimeric porphyrins subjected to fast atom bombardment mass spectrometry (FAB-MS), provide supporting evidence for the production of porphyrin excited states generated during the FAB process. Such excited states lead to intramolecular electron-transfer reactions, that can be investigated using FAB-MS. The excited state model is further developed when applied to two multicomponent porphyrins. Consideration of fragmentation and metal ion uptake by such compounds in FAB-MS allowed confirmation of the geometry of these porphyrins and also provided an understanding of the multiple intramolecular electron-transfer processes occurring. It is demonstrated that stringent geometry and symmetry requirements are needed for such molecules to function as special pair electron-donors in charge separation reactions.