Pentacyano(4-octadecylaminopyridine)ferrate(III) salts (POF) were synthesized and were shown to produce a stable Langmuir monolayer on a pure water subphase when the counter cation is chosen so as to enhance the hydrophobic character of this amphiphilic coordination compound. Second-harmonic generation measurements carried out on the monolayer indicated that POF molecules are very tilted and present a large second-order molecular hyperpolarizability. Langmuir-Blodgett (LB) films up to 60 layers were fabricated by means of the horizontal lifting method; however, X-ray diffraction experiments revealed an unexpected Y-type bilayer structure. The centrosymmetric character of these LB films was confirmed by the absence of a second harmonic generation property.