NEAR-IR SPECTROSCOPIC STUDIES OF MIXED-VALENCE DI-, TRI-, AND TETRAFERROCENE DERIVATIVES

Article abstract of DOI:10.1016/S0022-328X(00)99241-6

Near-IR data for a series of mixed-valence ?-bond bridged and ?-bond bridged di-, tri-, and tetra-ferrocene derivatives suggests intervalence electron transfer (IT) exists in all of the ?-bond bridged and some of the ?-bond bridged compounds.The compounds exhibiting the electron transfer transition include the mixed valence derivatives of 1,2-diferrocenylethene, 1,2-diferrocenyl-1,2-diphenylethene, azoferrocene, 1,1-diferrocenylethene, diferrocenyl ketone, ferricenyl(III)trisferrocenyl(II))borate zwitterion, triferrocenylphosphine oxide, diferrocenylphenylphosphineoxide and triferrocenylmethane.Compounds studied that do not exhibit the near-IR transition when oxidized are triferrocenylborane, triferrocenylphosphine, diferrocenylphenylphosphine and diferrocenylmethane.The near-IR transition in the ?-bond bridged derivatives is attributed to a predominantly through-bond mechanism while the transition in the ?-bond bridged derivatives is attributed to a through-space mechanism.It is suggested that the presence of the IT band in the phosphine oxides while being absent in the phosphine derivatives may be due to a difference in the dp-? overlap of phosphorus and the cyclopentadiene rings in the two systems.