Novel silicon naphthalocyanines: synthesis and molecular arrangement in thin films

Abstract

A series of highly organic-soluble [bis(trialkylsiloxy)]silicon tetrakis(alkylthio)-2,3-naphthalocyanines [(R¹₃SiO)₂SiNc(SR²)₄] have been synthesized, and their ¹H NMR, electronic absorption and fluorescence spectra measured. These spectra indicate that (R¹₃SiO)₂SiNc(SR²)₄ are monomeric in solution (10^–2–10^–7 mol dm^–3). In their solid films, all Q-band absorption maxima of (R¹₃SiO)₂SiNc(SR²)₄ are red-shifted from their monomeric Q-band maximum. The extent of shift significantly increases with decreasing R¹ length of the axial substituents, but the effect is far less with ring substituents, R². These observations are clearly explained using the exiton model. Our results indicated that novel naphthalocyanine (R¹₃SiO)₂SiNc(SR²)₄ molecules have a J-type molecular arrangement in thin solid films.