POLYMORPHISM IN POWDERS AND THIN-FILMS OF LITHIUM PHTHALOCYANINE - ANX-RAY, OPTICAL AND ELECTRON-SPIN-RESONANCE STUDY

The polymorphism of lithium phthalocyanine (PcLi) was studied for powd ers as well as for thin films deposited on glass substrate. Powders we re yielded by two electrochemical synthesis routes. While the powders obtained by electrochemical oxidation of PcLi, in acetonitrile and ace tone lead to an x structure, the synthesis route proposed by M.A. Peti t leads apparently to the ct form of PcLi. Their very different sensit ivity to oxygen, observed using electron spin resonance (ESR) spectros copy, is explained by means of the crystallographic structure of both polymorphs. Thin films were prepared by vacuum deposition and phase tr ansitions as well as preferential ordering of the crystallites are stu died as a function of increasing substrate temperature. While films de posited at low substrate temperatures, below 150 degrees C, lead to an x-like form with the molecular columns lying in the plane of the subs trate, the higher substrate temperatures favour the growth of the a fo rm and a loss in preferential ordering. Accordingly, changes in the se nsitivity to oxygen are followed as a function of substrate temperatur e.