The synthesis of a series of Re-I, Ru-II, and Os-II complexes that contain rigid polyphosphine/eumulene spacers is reported here. These cumulenic Ligands, namely, 1,1 ' ,3,3 ' -tetrakis(diphenylphosphino)allene (C3P4) and 1,1 ' ,4,4 ' -tetrakis(diphenylphosphino)cumulene (C4P4), utilize diphenylphosphino linkage components to coordinate to the metal-polypyridyl or metal-carbonyl units. Characterization of all mono-, homo-, and heterobimetallic complexes is achieved using P-31{H-1} NMR, IR, and fast atom bombardment mass spectroscopy (FAB/MS) and elemental analysis. The two Re-I homobimetallic complexes were also characterized by single-crystal X-ray structure determination, which provided the structural evidence of a 90 degrees rotation between the C-3 and C-4 adducts causing a change in the electrochemical behavior. The ground-state electronic absorption and redox interactions, along with the excited-state photophysical characteristics, are also explored. Electrochemical studies showed that an increase in the carbon chain length resulted in a greater amount of a-donation from the ligand to the metal centers, as well as a greater amount of electronic communication between the metal termini of the bimetallic species. The electronic absorption and emission spectra of the new complexes were also determined and characterized. The lifetimes of the excited-state luminescence of the Re-I mono-and homobimetallic complexes were found to be an order of magnitude shorter than the lifetimes of the heterobimetallic complexes containing the Ru-II and Os-II moieties. Excited-state energy transfer was observed from the higher MLCT excited state of the Re-I centers to the lower energy MLCT excited state of the Ru-II and Os-II centers on the following basis: no Re-I-based emission was detected in the steady-state emission measurements, the time-resolved decay traces were fitted to only single-exponential decays, and the quantum yields were identical for each compound at two different excitation wavelengths when different percentages of the metal-based chromophores were excited.