Synthesis, Structure, and Properties of Aromatic Ring-Layered Polymers Containing Ferrocene as a Terminal Unit

[2.2]Paracyclophane-layered polymers 4a and 4b end-capped by ferrocene and [2.2]paracyclophane, respectively, were synthesized by using a xanthene skeleton as a scaffold. Two model compounds, 4,5-bis(ferrocenylethynyl)-9,9-dimethylxanthene 7 and pseudo-p-bis(4-ferrocenylethynyl-9,9-dimethylxanthen-5-yl)[2.2]paracyclophane 8, comprising ferrocenes arranged in a face-to-face manner were also prepared. According to the X-ray molecular structure of compound 8, [2.2]paracyclophane between the ferrocenes had sufficient space for twisting and there was no interaction between two ferrocenes via [2.2]paracyclophane in the ground state. These polymers exhibited blue-light emission originating from the layered cyclophanes; however, the photoluminescence intensity of polymer 4a was lower than that of polymer 4b. The fluorescence emission of polymer 4a was effectively quenched by the end-capping ferrocene group.