One‐Electron Oxidized Copper(II) Salophen Complexes: Phenoxyl versus Diiminobenzene Radical Species

Oxidation Chemistry of Metal(II) Salen-Type Complexes

“…Another one-electron oxidized complex, [Cu(Salphen-OMe)]SbF6, has a different electronic structure from the previous two Salcn complexes [47]. The C-C and C-O bond lengths within the phenolate rings do not differ significantly from those of the complex before oxidation, Cu(Salphen-OMe).…”

“…Structures of three one-electron oxidized Cu II salen-type complexes are shown in Figure 6 [44,45,47]. X-ray analyses of all these complexes established that their structures are similar to those before oxidation, indicating a simple one-electron transfer from these precursors.…”

“…Such a trend is also applied to the salen-type complexes, and most of the Cu(II) and group 10 metal(II) salen-type complexes exhibited two reversible redox waves in the range of 0 to 1.5 V vs NHE, due to having two phenolate moieties [29][30][31][39][40][41][42][43][44][45][46][47]. On the other hand, the metal centered one-and two-electron oxidized complexes may possibly be generated in the similar potential range.…”

“…The present argument is focused on recent advances in the chemistry related with the synthesis, characterization, and reactivity of some of the one-electron oxidized metal(II)-salen type complexes, especially the complexes of group 10 metal(II) ions, Ni(II), Pd(II), and Pt(II) [39][40][41][42][43], and Cu(II) complexes [44][45][46][47] (Figure 3). Various useful and interesting salen-type complexes have been synthesized and characterized until now [48], and detailed electronic structural studies have recently been reported for a dinuclear chelating salen-type ligand having a catechol and a tetra(amino)tri(hydroxy)phenyl moiety [49,50].…”

“…The small potential differences are due to the substitution of the phenolate moiety and the ligand structure. However, there are some different electronic structures among the one-electron oxidized forms of the complexes in Table 1, i.e., a M III -phenolate ground state complex, a M II -phenoxyl radical where the radical electron is fully delocalized on two phenolate moieties, a relatively localized M II (phenolate)(phenoxyl) complex, and a M II (dinitrogen ligand radical)(phenolate)2 species [39][40][41][42][43][44][45][46][47]. The similarity of the potentials indicates that formation of all of the oxidized species is due to a simple electron transfer without significant structural changes.…”