Rationalized Approach to Molecular Tailoring of Polymetallocenes with Predictable Optical Properties

A rationalized approach to tuning the optical properties of metallocenes is reported. The optical properties of a series of high molecular weight polymetallocenes with main chain ferrocene or ruthenocene units were examined. The refractive indices of polymetallocenes were tuned from 1.599 to 1.747 by modifying the metal, the substituent group, or the spacer element. The molar refraction of the backbone repeating unit, RfcE, {where fc = [((eta)5C5H4)2Fe] and E = Si, Ge, Sn, or P} was calculated to range from 57.2 to 63.6 cm3/mol and demonstrated to comply to the additivity principle of molar refraction. The value of the molar refraction of the backbone repeating unit, RfcE, was used to predict the refractive index of molecularly tailored polyferrocenes. The optical dispersion of polyferrocenes, characterized by the Abbe number, was demonstrated to be lower than that of organic polymers with similar refractive indices.