Photooxidation and Photoconductivity of Polyferrocenylsilane Thin Films

Abstract

Irradiation of thin films of poly(ferrocenylmethylphenylsilane) ([Fe(η5‐C5H4)2SiMePh]n) cast from chloroform solution with UV light leads to photooxidation of ferrocene centers in the polymer main chain. The extent of the polymer oxidation can be controlled in the range ca. 0–5% by the duration of the irradiation exposure and by the concentration of chloroform. The photooxidized polyferrocenylsilane material is conductive, with an increased conductivity of greater than three orders of magnitude relative to the unoxidized material. In addition, the photooxidized polymers have been found to be photoconductive. The photooxidation process can be reversed by means of chemical reduction using hydrazine or decamethylferrocene, leading to the regeneration of the neutral polymers. However, substantial molecular weight decline was detected during the photooxidation/reduction process, presumably as a result of chain cleavage reactions induced by the anionic or radical chlorinated photoproducts. Methylation of the cyclopentadienyl rings of the ferrocene moiety in the polymer was found to lead to materials which are significantly more stable.Time trace of the current at constant applied voltage of 100 V for a PFS film upon illumination. The ON and OFF states were created by using a mechanical shutter.magnified imageTime trace of the current at constant applied voltage of 100 V for a PFS film upon illumination. The ON and OFF states were created by using a mechanical shutter.

Metallopolymers: New Multifunctional Materials

“…[56] When this amorphous polymer was cast from chloroform solution, the material was found to partially oxidise on exposure to UV radiation, and the extent of oxidation could be increased to a maximum of 5 % by conducting the procedure in chloroform vapour. This transformation resulted in an increase in dark conductivity by approximately three orders of magnitude, yielding a semiconducting film.…”

Polyferrocenylsilane‐Based Polymer Systems

“…[188] Photooxidation of amorphous polyferrocenylmethylphenylsilane thin films in the presence of chloroform and UV light leads to a significant increase of conductivity, potentially applicable to all-solid-state photoconducting and photovoltaic devices. [189] Controlled cross-linking of PFS yields redox-active solvent-swellable gels, potentially applicable as electrochemical actuators or switches. The swelling of these gels in organic solvents depends on the degree of oxidation at the iron sites, thereby allowing the development of planar colloidal photonic crystal devices, in which silica microspheres are periodically arrayed in a cross-linked PFS matrix.…”

Donor–Acceptor C60‐Containing Polyferrocenylsilanes: Synthesis, Characterization, and Applications in Photodiode Devices

“…[24][25][26][27] Photo-oxidation of PFS films can also be achieved by near-UV light irradiation in the presence of chloroform vapor, and the photo-oxidized PFSs show a conductive nature ($10 À8 SÁcm À1 ) in the dark and a photoconductive response under illumination. [28] Charge transfer complexes containing ferrocenes have been well investigated in the context of conducting and magnetic materials. [29] However, Guldi and co-workers recently reported intramolecular photo-induced electron transfer in ferrocene (donor)/fullerene (acceptor) dyads, and the photo-excited dyads consisting of a ferrocene radical cation and fullerene radical anion reveal relatively long-lived charge separation dynamics (on the order of microseconds).…”