Bridged ferrocenes

The visible and near ultraviolet absopriton spectra of a range of heteroannularly bridged ferrocene derivatives have been recorded and compared with those of analogous non-bridged compounds. The results have shown that the absorption bands appearing in this region are sensitive to the presence of ring substituents, particularly those capable of conjugative interaction with the cyclopentadienly system. The band appearing at 440 nm in the ferrocene spectrum also responds to ring-tilt deformation of the ferrocene nucleaus. The findings are discussed in relation to current theories of the electron structure of ferrocene.