New soluble bis[nona-, octa-, and pentamethylferrocenes] as ''molecular wires'' with a metal-to-metal distance of up to 40 angstrom

Methylated ferrocenes are useful building blocks for navel 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 pi-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 Angstrom and an effective conjugation pathway of up to 50 Angstrom.