Synthesis and long wavelength hyper-Rayleigh scattering measurements of extended μ-vinylidene di-iron donor based organometallic merocyanines

The synthesis is reported of a series of extended π-bridged organometallic merocyanines linking the dicyanovinyl electron accepting group with the electron donating [(CpFeCO)2(μ-CO)(μ-CCH)] fragment. The chromophores exhibited inverse solvatochromic shifts with increased medium polarity, which is because of interactions between dipolar or protic solvents and the dicyanovinyl unit. The nonlinear optical (NLO) properties of the chromophores have been investigated using long wavelength (1500 nm) hyper-Rayleigh scattering techniques to avoid both resonance and two-photon absorption enhancement of the first hyperpolarisabilities.