The versatility of cationic cyclopentadienyliron complexes is demonstrated for the generation of calix4]arene‐based dendrimers and polymers. Dendrimers were prepared from a branched organoiron calix4]arene through subsequent reactions of azo dyes and organoiron complexes. The resulting azo dye‐containing metallocalix4]arenes were soluble in polar organic solvents and displayed λmax ranging between 430 and 456 nm. Upon addition of various acids, the λmax shifted to higher wavelengths (513–535 nm). In the solid state and in solution, the azo dye‐containing metallocalix4]arenes reversibly changed colour in the presence of acid and base, indicating their potential use as acid sensors. Cyclic voltammetric studies showed that the iron centres of the metallocalix4]arenes were reversibly reduced at E1/2 = −1.49 V. When non‐branching organoiron‐based calix4]arene were reacted with dithiols, polymers containing calix4]arenes either in their side chains or main chains were obtained. The polymers possessed weight average molecular weights between 35 000 and 53 000. The polymers were determined to be thermally stable with backbone decomposition occurring above 500 °C.
