Evaporated thin films of trivalent - chloroindiumphthalocyanine (CIInPc) and chlorogalliumphthalocyanine (CIGaPc) - and tetravalent phthalocyanines - vanadyl-phthalocyanine (VOPc) and titanylphthalocyanine (TiOPc) - have been characterized by means of electronic absorption and infrared spectroscopy (both in transmission and reflection-absorption modes). It was found that the ability of self-organization clearly differs between trivalent and tetravalent phthalocyanine derivatives. The results revealed that CIGaPc and CIInPc thin films result to be highly organized. On the other hand, the evaporation of tetravalent phthalocyanines powders forms amorphous thin films. However, further film treatments (thermal annealing and solvent exposure) lead to the phase transition from amorphous to alpha-form, and as a result, a high degree of molecular organization is induced. (c) 2004 Elsevier B.V. All rights reserved.