New Hexaaza Macrocyclic Binucleating Ligands. Oxygen Insertion with a Dicopper(I) Schiff Base Macrocyclic Complex

Rached Menif, Arthur E. Martell, Philip J. Squattrito, Abraham Clearfield

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Abstract

Direct 2:2 condensation of isophthalaldehyde with diethylenetriamine produces a hexaaza 24-membered macrocyclic tetra Schiff base in good yield. The crystal structure of an isomeric form of the Schiff base is reported. Crystal data for N6C24H30·½MeOH: C2/c,a = 17.283 (2) Å, b = 16.930 (2) Å, c = 17.953 (3) Å, β = 118.73 (2)°, V= 4607 (2) Å3, Z = 8, R(F) = 0.059 for 1538 observations (I > 3(σ(I)) and 289 variables. The amber binuclear Cu(I) complex of the tetraaza macrocyclic Schiff base combines with a molar equivalent of dioxygen to form a green binuclear Cu(II) complex, which contains a bridging hydroxide ion and, by oxygen insertion, a bridging phenolate donor. These results provide the first macrocyclic tyrosinase model. Hydrogenation of the Schiff base provides the corresponding saturated hexaaza macrocyclic ligand. The protonation constants of the reduced macrocycle, as well as the binding constants of its mononuclear and binuclear Cu(Il) complexes, have been determined potentiometrically.

Original languageEnglish
Pages (from-to)4723-4729
Number of pages7
JournalInorganic Chemistry
Volume29
Issue number23
DOIs
StatePublished - 1990

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