Coordinating tectons: Bipyridyl terminated allenylidene complexes

A series of complexes with π-conjugated carbon chains terminated by bipyridyl moieties has been prepared. These allenylidene complexes were derived from 9-hydroxy-9-ethynyl-4,5-diazafluorene, the preparation of which is reported; the new allenylidene complexes are highly colored with the cumulated carbon chain terminating in a bipyridyl unit providing a site for further coordination. The synthesis, characterization, and X-ray structure determination of trans-[MCl(P∩P)₂=C=C=(4,5-diazafluoren-9-yl)]PF₆ (M = Ru, P∩P = bis(diphenylphosphino)methane (dppm), 1,2- bis(diphenylphosphino)ethane (dppe), 1,2-bis(dimethylphosphino)ethane (dmpe); M = Os, P∩P = dppm) are described. The effect of the variation in metal and ligand on electronic and electrochemical characteristics of these complexes has been investigated by using UV-vis, solution electrochemistry, and a combination of these techniques in spectroelectrochemical experiments. DFT calculations have been performed on trans-[RuCl(P∩P)₂ =C=C=(4,5-diazafluoren-9-yl) ^q (P∩P = dppm, bis(dimethylphosphino)methane (dmpm); q = -1, 0, + 1, +2) and subsequently solvent-corrected calculations with use of COSMO were also undertaken to examine the nature of electronic transitions in various oxidation states.