Supramolecular organization of subphthalocyanines in Langmuir and Langmuir-Blodgett films

Abstract

Interfacial studies of a series of subphthalocyanine (SubPc) macrocycles 1-3, 5 and 6, differently substituted either in the periphery (with polar and donor groups) or in the axial position of the macrocycle (with a chlorine atom or a trihexylsiloxy group), have been carried out. Remarkable changes in the orientation of the macrocycles at the air/water interface have been observed by varying the number of polar groups in the periphery or adding a bulky group in the axial position. The morphology of the monolayers has been carefully studied by Brewster angle microscopy. Monolayers made of compounds 1-3 could be efficiently transferred onto hydrophobic substrates. LB films of SubPc 1 were characterized in detail by UV-VIS and IR spectroscopies, and X-ray diffraction and ellipsometry experiments. These studies indicate that the LB films of SubPc 1 are surely Y-type, formed by layers of a well-defined average thickness of ca. 16 Å. Preliminary studies on the nonlinear optical (NLO) properties of these materials have been carried out. In particular, second harmonic generation (SHG) experiments have been performed on LB films of SubPc 1.