Abstract:
ABSTRACT: We synthesized a new class of picolylamine−porphyrin conjugates 1−
3 and have investigated the effect of heavy atom insertion on their intersystem
crossing efficiency through spin−orbit perturbations. By incorporating zinc ions in
the core as well as periphery positions of the porphyrin ring, we have successfully
optimized their triplet excited state quantum yields and their efficiency to generate
singlet oxygen. Uniquely, the picolylamine−porphyrin conjugate 3 having five zinc
ions exhibited a triplet excited state quantum yield of ca. 0.97 and a sensitized singlet
oxygen generation yield of ca. 0.92. In contrast, the free base porphyrin derivative 1
exhibited ca. 0.64 and 0.5 of the triplet excited state and singlet oxygen quantum
yields, respectively. Our results demonstrate that the insertion of zinc metal ions in
the picolylamine−porphyrin conjugates not only quantitatively enhances the triplet
excited state and singlet oxygen yields but also imparts hydrophilicity, thereby their
potential use as sensitizers in photodynamic therapy and green photooxygenation
reactions.
