Further optical studies on Langmuir-Blodgett films of octa-substituted metal-free phthalocyanines

Ellipsometry and optical spectroscopy in the ultraviolet-visible (UV-vis.) and infra-red ranges were used to study the correlation between structure and optical properties of Langmuir-Blodgett (LB) films of octa-substituted metal-free phthalocyanines containing different alkyl chains. The thickness and refractive index of LB films and the orientation of phthalocyanine moieties in the monolayer were obtained from ellipsometric measurements and then data were compared with those from II/A isotherms of the floating layer. UV-vis. absorption spectra of LB films of the molecules show Davydov splitting of the Q band. Small changes in alkyl length lead to significant changes in the Q-band shape. The optical characteristics of monolayers are found to be different from those of multilayer films. (C) 1997 Elsevier Science Ltd. All rights reserved