Photodynamics of [26]- and [28]hexaphyrin-bodipy hybrids

A set of hybrids having gradual variation in distances between hexaphyrin and bodipy moieties, given by uses of phenylene, biphenylene, and triphenyelene bridges was prepared. Efficient PET processes from bodipy (donor) to [26]- or [28]hexaphyrin (acceptor) were successfully observed, where the PET speed was controlled by intramolecular distances between the donor and the acceptor. UV irradiation at 515 nm raised a band corresponding to the bodipy absorption. As the time delayed, the bodipy bands decreased and new absorption bands at 615 and 580 nm corresponding to respective absorption bands of [28]- and [26]-hybrids gradually appeared. Whereas the femtosecond transient absorption spectra of [28]/[26]-hybrids having terphenylene bridges completely showed energy transfers from bodipy to hexaphyrin, irradiation of the hybrids using 615 and 580 nm pulses did not induce opposite ways of the PET process. On the basis of enlarged center-to-center-distances of [26]-hybrids than those of [28]-hybrids, the set of [26]-hybrids resulted in slow decay/rise processes. PET parameters obtained with the experiments were fairly consistent with the PET parameters calculated.