Building on a highly
efficient synthesis of pyrrole-appended isocorroles,
we have worked out conditions for manganese, palladium, and platinum
insertion into free-base 5/10-(2-pyrrolyl)-5,10,15-tris(4-methylphenyl)isocorrole,
H2[5/10-(2-py)TpMePiC]. Platinum insertion
proved exceedingly challenging but was finally accomplished withcis-Pt(PhCN)2Cl2. All the complexes
proved weakly phosphorescent in the near-infrared under ambient conditions,
with a maximum phosphorescence quantum yield of 0.1% observed for
Pd[5-(2-py)TpMePiC]. The emission maximum was found
to exhibit a strong metal ion dependence for the 5-regioisomeric complexes
but not for the 10-regioisomers. Despite the low phosphorescence quantum
yields, all the complexes were found to sensitize singlet oxygen formation
with moderate to good efficiency, with singlet oxygen quantum yields
ranging over 21–52%. With significant absorption in the near-infrared
and good singlet oxygen-sensitizing ability, metalloisocorroles deserve
examination as photosensitizers in the photodynamic therapy of cancer
and other diseases.