Singlet molecular-oxygen quantum yield measurements of some porphyrins and metalloporphyrins

Hematoporphyrin IX dimethyl ester (HPDME), tetraphenylporphyrin (TPP), tetra(4-methoxyphenyl)porphyrin (TMPP), tetra(3,4-dimethoxyphenyl)porphyrin (TDMPP), tetra(3,4,5-trimethoxyphenyl)porphyrin (TTMPP), tetraanthrylporphyrin (TAP) and tetraacridylporphyrin (TACP), and their Zn2+, SnX2(2+), Pd2+ and Pt2+ complexes have been prepared and characterized. The singlet molecular oxygen quantum yield (phi(DELTA)) values of the above porphyrins and their metal derivatives in N,N-dimethyl formamide (DMF) have been measured in the presence of 1, 3-diphenylisobenzofuran (DPBF) as O-1(2) acceptor using steady state technique after correcting for the intensity of light absorbed by the photosensitizers. The phi(DELTA) values for the free base porphyrins are usually around 0.60. Hematoporphyrin IX dimethyl ester and its metal derivatives follow the order: HPDME (phi(DELTA) = 0.60) > Zn HPDME (0.40) > PdHPDME (0.34) > Sn(OH)2HPDME (0.28) greater-than-or-equal-to PtHPDME (0.24). Zinc(II) complexes of tetraarylporpbyrins show about 65% efficiency in phi(DELTA) values are compared to the phi(DELTA) values of their corresponding free base porphyrins. These results can be explained on the basis of catalyzed intersystem crossing to the ground state. The phi(DELTA) values of the above free base porphyrins and their metal complexes in DMF in presence of DPBF using single-pulsed laser excitation technique follow similar trends