5-Aryl-1-ferrocenylpenta-1,4-dien-3-ones: Synthesis, structures, electrochemistry and third-order nonlinear optical properties

A simple method of synthesis of 5-aryl-1-ferrocenylpenta-1,4-dien-3-ones 5a–e is described. It consists of the condensation of 3-ferrocenylmethylidenepentane-2,4-dione with arenecarboxaldehydes in the presence of an aqueous alkali. Electrochemical and optical properties of the obtained ferrocenyl-containing dienones were studied. It was found that a reversible electron transfer Fc/Fc+ takes place in all compounds. In addition, a particular redox behavior of the pyridine moiety Py−/Py was detected in the molecule trans-/trans-1-ferrocenyl-5-p-pyridylpenta-1,4-diene-3-one 5c. The cubic nonlinear behavior of the synthesized compounds was tested in solid state at the wavelength range of 1100–1800 nm (telecommunications window). The third-order nonlinear susceptibility χ(3)(−3ω, ω, ω, ω), measured for polymer films doped with 30 wt.% of aryl(ferrocenyl)penta-1,4-dien-3-ones, was in the range of 1 and 2 × 10−12 esu. Compounds 5a, 5b, 5d and 5e showed, within the experimental error, very similar values for χ(3), which means that the phenyl (compound 5a), the p-methoxyphenyl (p-anisyl) (compound 5b), the ferrocenyl (compound 5d), and the p-fluorophenyl (compound 5e) groups give similar behavior for the third-order nonlinearities independently of the electronic effects of these substituents. On the other hand, the nonlinearities were partially enhanced by three-photon resonance.