Synthesis of unsymmetrical 1,8-naphthyridine-based ligands for the assembly of tri-and tetra-nuclear copper(ii) complexes

Abstract

A synthetic route for unsymmetrical 1,8-naphthyridine spacer based ligands is presented. Reaction of a 7-ethyldipyridyl-1,8-naphthyridine-2-carboxaldehyde intermediate with 2-aminophenol or 4,6-di-tert-butyl 2-aminophenol led to the ligands HL1 and HL2 respectively. Both...

Ligand Basicity and Chelate Effects on Sulfur Insertion vs. Sulfur Reduction by Zinc Thiolate Complexes

“…We attribute these first oxidations to that of the thiolate moiety to form the organic disulfide moieties, while the second oxidation waves likely correspond to the thiolate of [ 3 ] 2− and the phenoxide component of the oxidation product of [ 4 ] 2− . Reversible, ligand‐centered oxidation potentials of Cu 2+ and Ni 2+ 2‐amidophenolate complexes to the amidosemiquinonate and amidoquinone species have been reported at similar values [15] . The irreversible oxidation steps of [ 4 ] 2− suggest a more complicated mechanism, perhaps involving rearrangement similar to that of [ 1 ] 2− to [ 3 ] 2− .…”

“…Reversible, ligand-centered oxidation potentials of Cu 2 + and Ni 2 + 2-amidophenolate complexes to the amidosemiquinonate and amidoquinone species have been reported at similar values. [15] The irreversible oxidation steps of [4] 2À suggest a more complicated mechanism, perhaps involving rearrangement similar to that of [1] 2À to [3] 2À . These data indicate that the thiolate oxidation potential is largely independent of the phenoxide substituent and that sulfur reduction by [4] 2À occurs rather than sulfur insertion, due to stability of this oxidized and rearranged product(s).…”