C-Term Faraday Rotation in Low Symmetry tert -Butyl Substituted Polyferroceniums.

Molecular thin films are currently being investigated as candidate materials to replace conventional atomistic inorganic crystal-based Faraday rotators. High symmetry paramagnetic species have been reported to exhibit large Verdet constants via magnetic field splitting of degenerate ground states. However, lower symmetry open-shell species have not been extensively studied. Herein, we report the Faraday rotation of two poly di- tert -butylferroceniums with diphenylsilane and vinylene linkers. Thin films of oxidized poly[(1,1'-di- tert -butylferrocenyl)diphenylsilane] [ poly( t Bu 2 fc-SiPh 2 ) ] displayed a 30% increase in maximum Verdet constant relative to the previously reported decamethylferrocenium/PMMA composite, with Verdet constants of -4.52 × 10 4 deg T -1 m -1 at 730 nm and 4.46 × 10 4 deg T -1 m -1 at 580 nm. When a sp 2 -type linker was used, as with the oxidized poly(1,1'-di- tert -butyl-ferrocenylene)vinylene [ poly( t Bu 2 fc-C═C) ], negligible Faraday rotation was observed. Hence, Faraday rotation can be maintained when molecular symmetry is broken, however orbital symmetry breaking in optical transitions of interest leads to a significant loss in magneto-optical activity.