Photoinduced Electron Transfer Between Mono-6-p-nitrobenzoyl-ˉ-cyclodextrin and Adamantanamine-Cn-Co/Ni-porphyrins

Two series monotailed porphyrins, Cobalt-5-4-ω-(1-adamantaneamino) alkyloxyphenyl-10,15,20-triphenyl porphyrinate (CoPCnA, n=4,5,6) anj Nickel-5-4-ω-(1-adamantaneamino)alkyloxyphenyl-10,15,20-triphenyl porphyrinate (NiPCnA, n=4,5,6), were synthesized, in which the porphyrin moiety was connected to 1-adamantanamine via a flexible hydrocarbon chain. The fluorescence quenching between these donor substrates and mono-6-p-nitrobenzoyl-β-cyclodextrin (NBCD) was studied in detail. Distinct fluorescence quenching occured in these supramolecular systems. This quenching was attributed to the photoinduced electron transfer (PET) inside the supramolecular assembly between the porphyrin donors and cyclodextrin acceptors. Detailed Stern-Volmer constants were measured and they were partitioned into dynamic SternVolmer quenching constants and static binding constants. It was demonstrated that the PET interaction between the porphyrin subunits and NBCD is indeed effective.