New Soluble Bis[nona-, octa-, and pentamethylferrocenes] as “Molecular Wires” with a Metal-to-Metal Distance of up to 40 Å

Abstract

Methylated ferrocenes are useful building blocks for novel materials in molecular electronics with advantageous properties in comparison to normal ferrocene derivatives. The presence of nine, eight, or five methyl substituents leads to (i) a decrease in oxidation potential, (ii) amplified donor capacity with correspondingly increased stability of the ferrocenium salts, and, most significantly, (iii) increased solubility. A modular synthetic approach based on standard Wittig chemistry affords π-conjugated soluble nona-, octa-, and pentamethylated biferrocenes, bridged by up to five vinylene−phenylene subunits. These biferrocenes with spacers are “molecular wires” with a metal-to-metal distance of up to 40 Å and an effective conjugation pathway of up to 50 Å.

Syntheses, Structures and Nonlinear Optical Properties of Ferrocenyl Complexes with Arylethenyl Substituents

“…The crystallographic inversion center lies very close to the chromium atom, generating another molecule with a face to face disposition when compared with the previous one, thus resulting in disorder. The bond lengths and angles in 6 lie in the expected range, [13] with the ferrocenyl units adopting the sterically less hindered anti conformation. The cyclopentadienyl and phenyl rings in 6 are roughly coplanar (maximum dihedral angle 3.37°).…”

“…[8,13] For such complexes, and homologues with pentamethylcyclopentadienyl ligands, only one peak is observed for the oxidation of the iron atoms. However, the potential for this two-electron oxidation is sensitive to modification of the bridging unit; electrochemical data for compound 7 shows that the oxidation of the iron atom is clearly influenced by the carbonyl fragment.…”

Ferrocenyl‐Ended Thieno–Vinylene Oligomers: Donor–Acceptor Polarization and Mixed‐Valence Properties with Emphasis on the Raman Mapping of Localized‐to‐Delocalized Transitions

“…Keywords: ferrocenes · mixedvalent compounds · molecular materials · push-pull molecules · semiconductors an easily oxidizable compound and excellent electron donor which has been combined with conjugated molecules: thus, examples of diferrocenyl-polyenes, [6] diferrocenyloligo(pheA C H T U N G T R E N N U N G nylenevinylene) [7] , diferrocenyl-arenes [8] and others [9] have been reported. Also with oligothiophenes, Fc has been synthesized searching exploitable metal-to-ligand charge transfer and as molecular wire models since the occurrence of metal and organic conjugated sites.…”

Influence of Topology on the Long-Range Electron-Transfer Phenomenon

“…For instance, the solid-state structure of a bis-octamethylferrocenyl complex, bridged by one of the aforementioned units, showed that the vinylene, phenylene, and cyclopentadienyl subunits are twisted in relation to each other with torsion angles of 218 and 138. [21] It must be noted that, as far as intramolecular electrontransfer phenomena are concerned, the main distance to be considered is the through-bond distance between the two electron active sites; [20] that is, the sum of bond lengths corresponding to the conjugated pathway. These distances, measured from one radical alpha-carbon atom to the other, are 24.1 and 22.7 for diradicals 1 and 2, respectively.…”