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

Abstract

The 2,7-fluorenyl-bridged Fe(η 5 -C 5 Me 5 )(κ 2 -dppe)[C≡C(2,7-C 13 H 6 Bu 2 )C≡C]Fe(η 5 -C 5 Me 5 )(κ 2 -dppe) ( 1a ), its extended analogue Fe(η 5 -C 5 Me 5 )(κ 2 -dppe)[C≡C(1,4-C 6 H 4 )C≡C(2,7-C 13 H 6 Bu 2 )C≡C(1,4-C 6 H 4 )C≡C](η 5 -C 5 Me 5 )(κ 2 -dppe)Fe ( 1b ), and the corresponding mononuclear complexes Fe(η 5 -C 5 Me 5 )(κ 2 -dppe)[C≡C(2-C 13 H 7 Bu 2 )] ( 2a ) and Fe(η 5 -C 5 Me 5 )(κ 2 -dppe)[C≡C(1,4-C 6 H 4 )C≡C(2-C 13 H 7 Bu 2 )] ( 2b ), which model half of these molecules, have been synthesized and characterized in their various redox states. The molecular wire characteristics of the dinuclear complexes were examined in their mixed-valent states, with progression from 1a [PF 6 ] to 1b [PF 6 ] 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.