Photoinduced electron-transfer in porphyrin-acceptor cyclophanes, 19 - Pyromellitic diimide-porphyrin cyclophanes: Syntheses, transannular interactions, and structure analysis

The acceptor-porphyrin cyclophanes 2 and 4 with pyromellitic diimide (1) as strong electron-acceptor, and the corresponding porphyrin zinc complexes 3 and 5 were prepared by a route which differs considerably from that in the syntheses of previously prepared electron-acceptor porphyrin cyclophanes. The conformations of these electron-acceptor-porphyrin cyclophanes are disc ussed based on H-1-NMR and the X-ray structural analysis of 2. According to the results obtained, the plane of 1 and that of the porphyrin unit (at le ast in the crystalline state) are neither close nor parallel to each other. An unusual dihedral orientation of the donor and acceptor planes was detec ted for 2.