MESOGENIC METAL ALKYLTHIOPORPHYRINS FOR THE FORMATION OF LANGMUIR-BLODGETT-FILMS

The spreading monolayers at the air-water surface of the mesogenic, di scotic copper(II) derivatives of 2,3,7,8,12,13,17,18-octakis(alkylthio )porphyrin (Cu-TAP) have been characterized with the aim of finding th e best experimental conditions for fabricating Langmuir-Blodgett (LB) films with columnar aggregates having significant mono- and/or bidimen sional properties. The spreading isotherms of pure metal compounds wer e interpreted in terms of inhomogeneous, rigid surface films, not suit able for LB film deposition. A better transfer was reached with mixtur es (e.g. 1/20 molar ratio) of Cu-TAP with the film forming stearic aci d, 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.