Charge Injection and Transport in Metal-Containing Conducting Polymers: Spectroelectrochemical Mapping of Redox Activities

Abstract

Electropolymerization of tris(dioximate) cage complexes furnished metal-containing conducting polymers (MCPs) that deposit directly onto the electrode surface as uniform films. The injection of electrons into, or removal of electrons from, these electroactive materials proceeds via different pathways with different rates, the underlying molecular mechanisms of which were investigated by a combination of electrochemical, spectroscopic, and focused-ion-beam–scanning electron microscopy (FIB-SEM) cross-section analysis studies. For cobalt-containing polymers, both the metal centers and π-conjugated organic backbone work cooperatively as hopping stations for migrating holes, whereas the reduced polymer utilizes less-efficient self-exchange between cobalt(II) and cobalt(I) centers for electron transport. A small molecule model of such reductively doped polymer was prepared independently, which provided compelling electrochemical and spectroelectrochemical evidence to support the structural integrity of the metal centers upon redox switching. A well-defined metal-to-ligand charge transfer (MLCT) band of the n-doped polymer was exploited further as a straightforward spectroscopic tool to quantify the number of redox-active metal centers directly and to estimate the lower distance limit of diffusional charge transport across the bulk material.

Electrophilic Addition of Polyaromatic o-Quinones to an Iron(II) Diaminoclathrochelate Leading to the Macrobicyclic Iron(II) tris-Dioximates with Extended Annulated Ribbed Substituents

“…Intensity data for the complexes FeBd 2 ((Phn)Gm)(BF) 2 ·CHCl 3 and FeBd 2 ((Phen)Gm)(BF) 2 ·nCHCl 3 were collected on a Bruker Apex DUO CCD diffractometer equipped with a graphite-monochromated MoK a (l=0.71073 Å) radiation source at 150(2) K. The SMART software was used for data collection and also for indexing the reflections and determining the unit cell parameters; the collected data were integrated using SAINT software and corrected with SADABS [9] for absorption. The structures were solved by the direct method [10] and refined by full-matrix least-squares using SHELXTL software.…”

“…[1][2][3][4] Recently we described an iron(II) clathrochelate with annulated ribbed quinoxaline fragment that exhibited the reversible ligand-centered redox transformations coupled with electrochromism. [5] Its annulated azaheterocyclic moiety has been constructed using nucleophilic substitution of the reactive chlorine atoms in a dichloroclathrochelate precursor FeBd 2 (Cl 2 Gm)(BF) 2 (where Bd 2-and Cl 2 Gm 2-are α-benzildioxime and dichloroglyoxime dianions) (Scheme 1).…”

Ligand Effects in Low‐Valent Co(I) Clathrochelate Complexes

“…[8] In the meantime, the solid state structures of two other Co(I) clathrochelates have been reported: one complex with R = Cl and R' = Ph (E 1/2 = À 0.50 V), [8] and another complex with R = Ph and R' = dithiophenyl (E 1/2 = À 1.03 V). [9,10] Complexes with alkyl groups in lateral position display a more negative reduction potential (E 1/2~À 1.4 V), impeding isolation and structural characterization. A theoretical analysis of a Co(I) clathrochelate with R = Me came to the conclusion that the complex should feature a high spin Co(I) center (S = 1) in a highly symmetric ligand environment.…”

Mechanistic study of the formation of multiblock π-conjugated metallopolymer

“…This model fits the data from previously reported research [10][11][12], due to the "donor-acceptor" interactions between the π-conjugated unit and the transition metal ion in the adjacent monomer. The conductivity of these polymers is related to the electronic transfer (ET) from a metallic cation to the aromatic π-conjugated systems (innersphere ET through sequential hopping) [13,14]. In this way, the electropolymerization of the [N,N'-bis(salicylidene)-o-phenylenediamine]nickel(II) complex results in positively charged structures that form molecular columns, the positive charges being stabilized by negative ions inserted from the supporting electrolyte (counter ions) in the cavities of the polymers, which results in the formation of highly ordered and regular structures [8].…”