POLARIZED SPECTROSCOPIC STUDIES OF FERROCENYL LANGMUIR-BLODGETT ASSEMBLIES

Langmuir-Blodgett (LB) assemblies of a novel electron donor, 16-ferroc enylhexadecanoic acid [eta5-(C5H5)Fe(eta5-C5H4))(CH2)15COOH], have bee n prepared on a solid substrate. The structures of these LB assemblies have been characterized by polarized infrared (FT-IR) spectroscopy, e llipsometry, small-angle X-ray scattering, and UV-vis spectroscopy. Th e polarized FT-IR experimental results show that the LB assemblies are densely packed into microcrystalline structures with a triclinic or p seudohexagonal subcell packing form. A detailed analysis of the FT-IR dichroism suggests that the axis of the all-trans hydrocarbon chains o f the functionalized ferrocene fatty acid is tilted approximately 27-d egrees from the surface normal and the cyclopentadienyl ring of the fe rrocene chromophore in the LB assembly has a tilt angle of 53-degrees with respect to the substrate surface normal. It is also shown that th ese terminal ferrocene chromophores have a preferential orientation pe rpendicular to the film transfer direction. This is presumably due to the formation of aggregates between ferrocene chromophores in the LB a ssembly; aggregate formation is detectable from shifts of the UV-vis a bsorption in the films compared with the spectrum in solution.