Synthesis of Azo-Bridged Ferrocene Oligomers and a Polymer and Electrochemical and Optical Analysis of Internuclear Electronic Interactions in Their Mixed-Valence States

Abstract

New azo-bridged ferrocene trimers, Fc-Fc'-N=N-Fc (2) and Fc-N=N-Fc'-N=N-Fc (3), where Fc and Fc' refer to (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4)-) and Fe(eta(5)-C(5)H(4)-)(2), respectively, were obtained in the reaction of a mixture of lithioferrocene and 1,1'-dilithioferrocene with N(2)O. X-ray crystallography of azoferrocene (1) has determined that the Fe-Fe distance is 6.80 Å in the trans form. Cyclic voltammograms of 3 in aprotic solvents such as CH(2)Cl(2) or THF exhibit reversible 2e(-) and 1e(-) oxidation waves, indicating that the positive charge in the monocation is localized mostly on the terminal ferrocene unit (correspondingly, Fc(+)-N(2)-Fc'-N(2)-Fc) due to a strong electron-withdrawing effect of the azo group. This charge distribution in the mixed-valence state is supported by the characteristics of intervalence-transfer (IT) bands. An asymmetrical complex, 2, undergoes a three-step 1e(-) oxidation, and the two mixed-valence forms can be roughly expressed as Fc(+)-Fc'-N(2)-Fc and Fc(+)-Fc'-N(2)-Fc(+). The redox potentials and IT band characteristics of 1(+), 2(+), and 2(2+) depend markedly on the solvent. The solvent effect of the IT band on nu(max) cannot be interpreted only by the parameters in the Marcus-Hush theory, indicating that the nature of the solvent as donor or acceptor should be taken into account in the electron-exchange process in the mixed-valence states. More donating solvent affords higher IT and LMCT energy, indicating the hole-transfer mechanism. The reaction of 1,1'-dilithioferrocene and N(2)O gives a polymer composed of [-(Fc'-N=N-Fc')(0.6)-(Fc'-Fc')(0.4)-](n)().

Synthesis of Azoimidazolium Dyes with Nitrous Oxide

“…[6] A second, and much less explored direction is the utilization of N 2 O as a building block for more complex organic molecules. [7][8][9][10] Organometallic compounds of the alkali [7] and earth alkaline metals [8] are known to react with N 2 O under mild conditions. The products contain nitrogen atoms from N 2 O, but the reactions are often not very attractive from a synthetic point of view (e.g., poor yields are obtained or alternative procedures give better results).…”

Sandwich Complex‐Containing Macromolecules: Property Tunability Through Versatile Synthesis

“…Like other macromolecules, sandwich complex‐containing macromolecules can be obtained through step polymerization mechanisms, which include esterification, hydrosilylation, amidation, and aromatic substitution, as well as other substitution reactions. These step polymerization reactions offer the opportunity to tune the properties of the sandwich complex‐containing macromolecule through the incorporation of various spacers . Electronics as well as the structure of the spacers tunes electronic interaction between the metal centers, solubility, and thermal properties of the resulting polymer.…”

Metallocene-containing conjugated polymers

“…[332,[446][447][448]. A family of 3-ferrocenylazobenzene-attached dendrimers, 9-mer, 27-mer, and 81-mer, was synthesized [449] which exhibited photochromism and photoisomerization.…”