2,7-Fluorenediyl-Bridged Complexes Containing Electroactive Fe(η5-C5Me5)(κ2-dppe)CC- End Groups: Molecular Wires and Remarkable Nonlinear Electrochromes

The 2,7-fluorenyl-bridged Fe(eta(5)-C5Me5)(kappa(2)-dppe) [C C(2,7-C13H6Bu2)C C]Fe(eta(5)-C5Me5) (kappa(2)-dppe) (1a), its extended analogue Fe(eta(5)-C5Me5)(kappa(2)-dppe)[C C(1,4-C6H4)C C(2,7-C13H6Bu2)C C(1,4-C6H4)( C](eta(5)- C5Me5)(kappa(2)-dppe)Fe (1b), and the corresponding mononuclear complexes Fe(eta(5)-C5Me5)(kappa(2)-dppe)[C C(2-C13H7Bu2)] (2a) and Fe(eta(5)-C5Me5)(kappa(2)-dppe)[C C(1,4-C6H4)C C(2-C13H7Bu2)] (2b), which model half of these molecules, have been synthesized and characterized in their various redox states. The molecular wire chatacteristics of the dinuclear complexes were examined in their mixed-valent states; with progression from 1a[PF6] to 1b[PP6] resulting in a sharp decrease in electronic coupling. The, cubic nonlinear optical properties of these species were investigated over the visible and near-IR range, a particular emphasis being placed on their multiphoton absorption properties; the complexes are shown to function as redox-switchable nonlinear chromophores at selected wavelengths, and the more extended derivatives are shown to exhibit the more promising NLO performance.