Nonlinear optical properties and application of a chiral and photostimulable iron(II) compound

Abstract

We measure linear absorption, circular dichroism, second harmonic, and sum frequency generation in the [Δ-Fe(phen)3](Δ-As2(tartarate)2), [Λ-Fe(phen)3](Λ-As2(tartarate)2) enantiomers of an Fe(II) complex. In the solid state, the chirality of this compound results from the introduction of the (As2(tartarate)2) chiral anions. Linear absorption and X-ray diffraction indicate that Fe(II) is in the low-spin state. Circular dichroïsm reveals that in the solid state, these compounds are chiral, whereas the complexes racemize in solution. A large second harmonic generation signal is recorded using thin films from these two enantiomers. The second-order susceptibility χ111(2) of these compounds is evaluated across the visible spectral range. It displays a resonance at 520 nm, which is associated with the metal-to-ligand charge transfer occurring within the complex. At its maximum, χ111(2) = 6.4 pm V−1 is more than 1.4 times larger than the well-known beta-BaB2O4 nonlinear crystal (χ122(2) ∼ 4.4 pm V−1). Finally, we demonstrate a useful application for a thin film from this compound, which characterizes the cross-correlation of two femtosecond laser pulses.