Metal-centered redox activity in a polymeric Cobalt(II) complex of a sterically hindered salen type ligand

A Novel Cobalt Metallopolymer with Redox-Matched Conjugated Organic Backbone via Electropolymerization of a Readily Available N4 Cobalt Complex

“…In contrast to polymeric cobalt complexes of N 2 O 2 Salen-type ligands exhibiting the Co(II)/Co(III) conversion at lower potentials than the potentials of organic backbone oxidation [8,9], the findings of this study demonstrate that the metal-centered redox activity in poly-[Co(Amben)] is located at potentials matching the redox potentials of the organic backbone (more specifically, between the potentials of neutral/radical cation and radical cation/di-cation redox conversions) and corresponding to a highly conductive state of the polymer film. Such difference is apparently the effect of replacing phenoxo oxygen by anilido nitrogen in the coordination sphere of the monomer.…”

“…The resulting metallopolymers are electrochemically active, electrochromic, conductive in the doped state, and prone Polymers 2021, 13, 1667 2 of 16 to multi-electron redox reactions, which allows their use in energy storage systems [4], electrochromic devices [5], electrocatalytic systems [6], and photoelectrochemical cells [7]. Among various known polymeric Salen-type complexes, Cobalt Salen-type polymers are of special interest because they exhibit both metal-and ligand-based redox activity [8][9][10][11]. This contrasts with more well-studied Ni-and Cu-based Salen-type polymers that are converted from neutral to oxidized state via ligand-based redox reactions involving consecutive formation of cation radicals and di-cations in biphenyl fragments, while metal centers act as structuring and redox-mediating units [12][13][14].…”

“…"Anilinosalen" N 4 analogues of N 2 O 2 [Co(Salen)]-type complexes, also referred to as cobalt(II) complexes of "Amben"-type ligands (Scheme 1), have been studied since the 1970s [21][22][23][24]. Recent research on the electronic structure of one-electron, oxidized, protected [Co(Amben)]-type complexes [25,26] clearly shows that their first oxidation is a ligand-based process yielding Co(II)-anilinyl radical cation species, in contrast to the metal-based first oxidation of [Co(Salen)]-type complexes [3] and corresponding metallopolymers [8,9]. Unprotected [Ni(Amben)] and [Pd(Amben)] exhibiting ligand-based oxidation were demonstrated to undergo electro-oxidative polymerization, resulting in the formation of electroactive polymers [27], and we very recently reported the results of detailed studies on poly-[Ni(Amben)] electrochemistry [28].…”

New Variant of Electrochemical Intercalation Isotherm: Analysis of Instability Region Dependence on Electrolyte Concentration

“…Second is the reformulated isotherm (eq 2) proposed by Vorotyntsev et al; 20 it applies mostly for the description of electroactive polymers. 21,22 Reformulation of the Langmuir− Frumkin isotherm accounted for the phase character of the material. Simply speaking, the model states that the total potential drop between the metal substrate (current collector) and the electrolyte solution is divided into two main parts: one occurs at the metal substrate/redox material border, while the other is at the redox material/electrolyte solution border.…”

“…To the best of our knowledge, the form of Langmuir–Frumkin type of electrochemical intercalation isotherm is independent of the electrolyte concentration (in a sense that the change of concentration of the bathing electrolyte solution does not influence the shape of the isotherm, the midwidth of the differential version of the isotherm, and so forth); concentration changes lead solely to the shift of the isotherm as a whole along the potential axis. Second is the reformulated isotherm (eq ) proposed by Vorotyntsev et al; it applies mostly for the description of electroactive polymers. , Reformulation of the Langmuir–Frumkin isotherm accounted for the phase character of the material. Simply speaking, the model states that the total potential drop between the metal substrate (current collector) and the electrolyte solution is divided into two main parts: one occurs at the metal substrate/redox material border, while the other is at the redox material/electrolyte solution border.…”