The molecular first hyperpolarizability, beta, and the X-ray crystal structure of the complex [Fe(eta(5)-C5H5) ((R)-PROPHOS)(p-NCC6H4NO2)][PF6] ((R)-PROPHOS = (R)-(+)-bis-(1,2-diphenylphosphino)propane) were determined. A near-resonant enhanced beta value as high as 545 x 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. (C) 2002 Elsevier Science B.V. All rights reserved.