Macrocycle–pore network interactions: Aluminum tetrasulfophthalocyanine in organically modified silica

A dependable method was implemented for finding appropriate experimental conditions to attain a disaggregated trapping of aluminum phthalocyanine molecules inside translucent silica pore networks. Aluminum hydroxy-tetrasulfophthalocyanine was chosen as probe species for this task in view of its high colloidal stability and exceptional fluorescence. During early experiments, the fluorescence and stability of the trapped probe species either disappeared or were attenuated due to the interactions with the silanol groups residing on the pore walls. The stability disadvantage was overcome by chemically exchanging the surface silanol groups of silica by longer alkyl or aryl groups proceeding from organo-substituted alkoxides. The interactions between these groups and the aluminum probe induced its aggregation, degradation or the contraction or expansion of the cavities lodging these molecules. Although the red fluorescence of the probe molecule disappears when it was physically trapped in organo-modified silica, the results here presented revealed the possibility of adjusting the shape, pore size, specific surface area, and internal polarity of the pore cavities through the use of organo-substituted alkoxides and templating species, such as phthalocyanines. Hybrid systems generated this way can become important for nanotechnological applications in catalysis, optics, medicine, and gas sensoring.

Research highlights
► The materials consisting of singly aluminum phthalocyanine trapped in organo-modified silica.
► Aggregation or stability of the macrocycle trapped in modified silica depends on the alkyl identity.
► Pore sizes, and surface area depend on the identity nature of alkyl group attached to the modified SiO2 network.
► Hybrid systems design is possible by combining macrocycles and organo substituted alkoxides.