Low to moderate molecular weight substituted polyferrocenylenes [(eta(5)-C5H3X)Fe(eta(5)-C5H3X)](n) (where 3a-3c, X = H, SiMe3, Me) were prepared from the Ullmann coupling reaction of the diiodoferrocenes, (eta(5)-C5H3XI)(2)Fe (2a-2c), with an excess of copper metal or alternatively CuCl-facilitated coupling of the bis(stannyl)ferrocene, (eta(5)-C5H3SiMe3SnBu3)(2)Fe (1b). The new monomers were characterized by H-1 and C-13 NMR spectroscopy, elemental analysis and mass spectrometry. A single-crystal X-ray diffraction study (eta(5)-C5H3SiMe3I)(2)Fe (2b) shows the disubstituted cyclopentadienyl rings are eclipsed with the substituents staggered by 20degrees. The molecular weights (M-w) for the soluble homopolymers 3b and 3c were estimated by gel permeation chromatography in THF vs polystyrene standards and were found in the range from 2.0 x 10(3) to 1 x 10(4) with generally broad polydispersities (PDI > 2). Polymers 3b and 3c were characterized by H-1 and C-13 NMR spectroscopy and elemental analysis. The polymer thermal transition behavior and morphology of 3a-3c were examined by differential scanning calorimetry (DSC) and by powder X-ray diffraction (PXRD). The amorphous nature of the disubstituted polymers 3b and 3c was evident by the presence of weak glass transitions and the absence of any melt transitions. In contrast, the semicrystalline nature of the largely insoluble polyferrocenylene 3a led to the presence of a strong melt transition by DSC in addition to three sharp peaks in its the PXRD spectrum. The polymers 3b and 3c as well as their I-2 and TCNE oxidized products (4b, 4c and 5b, 5c) were characterized by UV/vis/NIR spectroscopy. The neutral polymers 3b and 3c showed only weak d-d visible transition centered near A = 480 pm, while the partially oxidized derivatives showed strong charge-transfer peaks in the visible (lambda = 630-700 nm) and broad intervalence charge-transfer transitions between lambda = 850 and 1900 nm. Cyclic voltammetry of the neutral polymers 3b and 3c showed two well-separated oxidation waves with DeltaE(1/2) values of 485 and 460 mV s(-1) respectively and were consistent with substantial interaction between neighboring metal centers. Mossbauer data of the partial oxidized dimethylferrocene polymer 5c with TCNE at room temperature indicates that electron transfer is valence trapped with distinct Fe2+ and Fe3+ sites.