Single Two-Electron Transfers and Successive One-Electron Transfers in Biferrocenyl−Indacene Isomers

Abstract

Novel biferrocenyl complexes of s-and as-dihydroindacenes have been prepared and the charge transfer properties of their mono-and dicationic derivatives, selectively generated by one-electron and two-electron oxidation, have been investigated. Mixed-valence cations are generated by chemical oxidation using acetylferricinium as an oxidant agent and monitored in the visible, IR, and near-IR regions. The IT bands in the near-IR spectra are rationalized in the framework of Marcus-Hush theory. The rigid and planar indacene platform bonded to two terminal redox groups displays a redox chemistry that can be switched from single two-electron transfers to two successive one-electron transfers by changing the supporting electrolyte from nBu 4 NPF 6 to nBu 4 NB(C 6 F 5 ) 4 . § Dedicated to Prof. J€ urgen Heck on the occasion of his 60th birthday.

Key multi(ferrocenyl) complexes in the interplay between electronic coupling and electrostatic interaction

“…Much better results and agreement with the theoretical treatment are usually provided by optical investigations in the NIR region where mixed-valence species typically absorb. Indeed, we have recently synthesized the bis(ferrocenyl) complexes of s-and as-indacenes, 7a and 7b, 34 demonstrating that the rigid and planar indacene platform bonded to two terminal redox groups displays a redox chemistry that can be switched from a single two-electron transfer, using nBu 4 NPF 6 as the supporting electrolyte, to two successive one-electron transfers with nBu 4 NB(C 6 F 5 ) 4 .…”

“…52 Metal-metal electron delocalization in linkage structures assembled via noncovalent are extremely rare. Kaifer 53 reported the preparation and properties of a ferrocene derivative containing a quadruple hydrogen bonding motif designed to self-recognize, forming a fascinating highly stable hydrogenbonded dimer that contains two identical ferrocene centres separated by more than 10 Å (34).…”

Bis-porphyrin copolymers covalently linked by pyridinium spacers obtained by electropolymerization from β-octaethylporphyrins and pyridyl-substituted porphyrins

“…Thus, in this case, the two waves assigned to the successive one-electron reductions of the pyridinium spacers observed both for poly-trans-H 2 Py 2 Ph 2 P-ZnOEP and poly-cis-H 2 Py 2 Ph 2 P-ZnOEP copolymers (obtained from the cis-and the trans-H 2 Py 2 Ph 2 P macrocycles, respectively) indicate interactions existing both for substitutions in cis-and trans-positions onto the same H 2 Ph 2 P macrocycles. This aspect has been initially studied by Evans, 35 then by Save´ant 36,37 and by Amatore 38,39 and more recently by Santi et al 40 for monomeric systems in solution where conformational changes play a major role in these phenomena, as well the solvent reorganisation, the nature of the supporting electrolyte, the conjugation and of course electrostatic interactions (more especially in the case of polymers). It is therefore not surprising to observe different behaviours in the copolymers obtained compared to monomer species dissolved in solution.…”

Synthesis and Characterization of Diferrocenyl Conjugates: Varying π‐Conjugated Bridging Ligands and its Consequence on Electrochemical Communication

“…Later, Santi and coworkers reported two biferrocenyl complexes of s-and as-dihydroindacenes. [29] Electrostatic repulsion contributes mostly to electronic communication in nonlinear as-indacene bridge, whereas in s-indacene it occurs via through-bond process due to better conjugation. Subsequently, Nemykin and co-workers also demonstrated electrostatic interactions between the two ferrocenyl termini in 3,4-diferrocenylpyrrole complexes.…”