Linear and non-linear optical properties of areneFeCp complexes

Ionic [areneFeCp]+ fragments were used as electron acceptors in combination with dimethylamino or pyridoneiminyl donors to form push–pull substituted chromophores. While a tolane derivative showed high second-order non-linear optical activity (measured by hyper-Rayleigh scattering), an analogous pyridoneimine derivative did not. With the help of an X-ray crystal structure analysis this discrepancy was traced back to a cyanine-like structure of the imine. Semiempirical INDO/S calculations support this conclusion.