High first hyperpolarizability and perfectly aligned crystal packing for an organometallic compound [Fe(η5-C5H5)((R)–PROPHOS)(p-NCC6H4NO2)][PF6]·CH2Cl2

The molecular first hyperpolarizability, β, and the X-ray crystal structure of the complex [Fe(η5-C5H5)((R)–PROPHOS)(p-NCC6H4NO2)][PF6] ((R)–PROPHOS=(R)–(+)-bis-(1,2-diphenylphosphino)propane) were determined. A near-resonant enhanced β value as high as 545×10−30 esu was obtained from hyper-Rayleigh scattering measurements. In addition, the compound crystallizes in the space group P1 with a perfect alignment of the dipolar molecules (only a single chromophore per unit cell), thus maximizing the macroscopic nonlinearity for electro-optic or parametric frequency conversion applications. The molecular packing in the crystal is analyzed in order to understand the factors leading to the perfect alignment.