Covalent Anchoring of Phthalocyanines on Silicon Dioxide Surfaces:  Building up Mono- and Multilayers

Ruthenium phthalocyanine (RuPc) monolayers were obtained by self-assembly on pyridino-functionalized metal oxide substrates, by coordination between the ruthenium ions and the pyridino groups. The substrates were functionalized by silanization with a bifunctional silane. Soluble ruthenium phthalocyanines, axially coordinated by labile benzonitrile groups, were used. A ligand exchange reaction was involved, one benzonitrile group being replaced by pyridine. These RuPc monolayers were characterized by transmission UV−vis spectroscopy, atomic force microscopy, polarization modulation infrared reflection−absorption spectroscopy, and time-of-flight secondary ion mass spectrometry. A second ligand exchange reaction allowed us to build RuPc bilayers by two different strategies. A mixed RuPc/cobalt porphyrin bilayer was also obtained.