Mesogenic metal alkylthioporphyrins for the formation of Langmuir-Blodgett films

The spreading monolayers at the air-water surface of the mesogenic, discotic copper(II) derivatives of 2,3,7,8,12,13,17,18-octakis(alkylthio)porphyrin (CuTAP) have been characterized with the aim of finding the best experimental conditions for fabricating Langmuir-Blodgett (LB) films with columnar aggregates having significant mono- and/or bidimensional properties. The spreading isotherms of pure metal compounds were interpreted in terms of inhomogeneous, rigid surface films, not suitable for LB film deposition. A better transfer was reached with mixtures (e.g. molar ratio) of Cu-TAP with the film forming stearic acid, thus obtaining stable and reproducible LB films with more than 300 layers. The film maintained a disordered state of columnar aggregates as proved by electron spin resonance and UV-visible spectroscopy