Transmission electron microscopy of stearic acid Langmuir-Blodgett films with incorporated ruthenium(II) tris(2,2′-bipyridyl) complex

Abstract

Monolayer Langmuir-Blodgett (LB) films of stearic acid and Ru(bpy) 3(ClO 4) 2 (bpy is 2,2′-bipyridyl), Ru(tmbpy) 3(ClO 4) 2 (tmbpy is 4,4′,6,6′-tetramethyl-2,2′-bipyridyl) of varying ratios and of an amphiphilic Ru(II) complex have been produced. Comparison of pressure-area isotherms for pure stearic acid with the mixed films of stearic acid with metal complexes indicates that the molecular area is determined only by the fatty acid. The absence of any contribution of the metal complex to the molecular area for the mixed film suggests that the metal complex may reside beneath the stearic acid film (ion paired with the hydrophilic head group). Transmission electron microscopy and the cyclic voltammogram for the LB films of varying concentration indicate the presence of the Ru(II) complex in mixed LB films of different molar ratios of stearic acid and Ru(bpy) 3(ClO 4) 2 and in a pure amphiphilic Ru(II) complex film. The atomic force microscopy images, on the contrary, support the close packing of the stearic acid in the mixed films implying that the metal complex does not disturb the stearic acid packing.