Synthesis and electrochemistry of dimanganese(II) complexes of phenol-based dinucleating ligands with four methoxyethyl chelating arms

Abstract

Dimanganese(II) complexes [Mn₂(bonp)(PhCO₂)₂]PF₆ (1) and [Mn₂(bocp)(PhCO₂)₂]PF₆ (2) were synthesized with p-nitro- and p-chloro-substituted phenol-based dinucleating ligands bonp^- [2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-nitrophenolate anion] and bocp^- [4-chloro-2,6-bis[bis(2-methoxyethyl)aminomethyl]phenolate anion], respectively, with the aim of controlling the redox potentials of the dimanganese center by changing the p-substituents in the dinucleating ligands. Cyclic voltammograms of 1 and 2 showed quasi-reversible oxidation processes, assigned to Mn^IIMn^II/Mn^IIMn^III, at 1.17 and 1.00 V vs. Ag/AgCl, respectively. Compared to the previous p-methyl complex [Mn₂(bomp)(PhCO₂)₂]PF₆ (3) [bomp^–: 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenolate anion] (0.96 V vs. Ag/AgCl), the order of the potentials was 1(-NO₂) > 2(-Cl) > 3(-CH₃). Thus, the redox potentials of the dimanganese centers were controlled by the p-substituents in the dinucleating ligands.