Di(biferrocenyl)ethyne (3) and -butadiyne (4) have been prepared by Negishi, Eglinton and Sonogashira C, C cross-coupling reactions using bfc-I (1) and bfc-C CH (2) (bfc = 1:1 ''-biferrocenyl) as starting materials. Compound 4 was structurally analyzed by single crystal X-ray diffraction studies. The individual ferrocenyl units are all coplanar and anti-parallel oriented. Electrochemical measurements showed that all four ferrocenyl units can reversibly be oxidized. The electrochemical characteristics of these molecules represent a combination of the properties of biferrocene and the appropriate ferrocenyl analogs diferrocenyl ethyne and diferrocenyl butadiyne, respectively. While the dicationic oxidation state of both compounds showed characteristics of a charge transfer within the biferrocenium units, the tricationic form allows electron transfer through the (-C C-) n (n = 1, 2) functionalities. The observed inter-valence charge transfer (IVCT) interaction of 3 and 4 in any mixed-valent oxidation state allowed the characterization of these species as class II systems according to Robin and Day. In situ IR spectroscopy of 3 and 4 showed that within 3(n+) and 4(n+) (n = 0, 2, 4) no nu(C)(C) band is present, while 3(+) and 3(3+) showed two nu(C)(C) stretching vibrations due to Fermi resonance. Compound 4(3+) exhibits only one sharp nu(C)(C) frequency. (C) 2013 Elsevier B. V. All rights reserved.