Manganese(III) complexes of 1,2-bis(2-pyridinecarboxamido)benzene: synthesis, spectra, and electrochemistry

The synthesis and solution properties of the high-spin (µeff.= 4.78–4.86 at 298 K) manganese(III) complexes [Mn(bpb)X][X = Cl–, N3–, or SCN–; H2bpb = 1,2-bis(2-pyridinecarboxamido)benzene], are described. The brown crystalline complexes display ligand-to-metal charge-transfer transitions at ca. 430 nm, while in the near-infrared region crystal-field transitions are observed. In N,N-dimethylformamide solution the complexes exhibit a quasi-reversible MnIII–MnII couple [E298°–0.03 to + 0.03 V vs. saturated calomel electrode (s.c.e.)]. The complexes [Mn(bpb)Cl] and [Mn(bpb)(N3)] display an additional quasi-reversible MnIV–MnIII couple [E298°+0.87 (Cl–); + 0.49 V (N3–)vs. s.c.e.].