SYNTHESIS AND PHOTOPHYSICS OF DIAZA-CROWN ETHER-BASED BISPORPHYRINS

Article abstract of DOI:10.1002/poc.610071003

The bisporphyrin N,N'-bis<4''-(meso-triphenylporphyrinyl)benzyl>-4,13-diaza-18-crown-6 and its mono- and dizinc derivatives were synthesized in 66percent, 46percent and 53percent yields, respectively, from 5-(4'-bromomethylphenyl)-10,15,20-triphenylporphyrin or its zinc derivative and 4,13-diaza-18-crown-6.The zinc-containing bisporphyrins form dimers in solution at low temperature or at high concentration.The unsymmetrical bisporphyrin; monozinc N,N'-bis<4''-(meso-triphenylporphyrinyl)benzyl>-4,13-diaza-18-crown-6 shows singlet-singlet energy transfer from the zinc porphyrin moiety to the free base moiety in both the monomeric and the dimeric form.The energy transfer rates were determined using time-resolved fluorescence spectroscopy and were found to be 1.26x10⁹ and 2.29x10⁹ s^-1 for the monomeric and dimeric form, respectively.The difference in energy transfer rates between the two forms can be rationalized by the difference in overlap between the donor fluorescence spectrum and acceptor absorption spectrum, donor-acceptor distance and donor-acceptor orientation.