Porphyrazines and norphthalocyanines bearing nitrogen donor pockets: Metal sensor properties

The amino-functionalized porphyrazines 1, 2, and 4 and norphthalocyanines 3 and 5, which were prepared via Linstead macrocyclization reactions of dinitrile precusors, were subject to UV-vis titrations in the presence of inorganic ions. These polydentate macrocycles are able to bind metal ions by the peripheral ligating diazacrown or vicinal diamine entities in addition to metal ion binding within the porphyrazine (norphthalocyanine) cavity. Although 1 only weakly bound Ag(I) and Hg(II), 2 to 5 were superior polydentate ligands. Surprisingly, porphyrazine 4 was a superior ligand for binding 4 equiv of Co(II), Cu(II), Zn(II), and Cd(II) than the corresponding tetracrowned porphyrazine 2. Both 2 and 4 were excellent ligands for peripherally complexing 4 equiv of Ag(I) and Hg(II) and only for one metal, Pb(II), was the crowned system 2 superior to 4. The crowned norphthalocyanine 3 was generally inefficient in the peripheral complexation of inorganic cations, whereas 5 was superior for the peripheral binding of Co(II), Cu(II), Zn(II), Cd(II), and Hg(II) (1 equiv). Again, only with Pb(II) was the crowned system 3 a superior ligand to 5. X-ray crystallographic characterization of diazacrown 12a, porphyrazine 1 (M = Mg), and the complexes of crown 12b with Cu(BF4)(2) and with HClO4 are reported.