Dimerization of metallophthalocyanines in inorganic matrix

Metallophthalocyanine (MPc) and its composites have excellent photo-electricity properties. Here we report the study of MPc doped silica xerogel matrix obtained by sol–gel technique. Because the issue of dimerization is vital in determining the optical properties of dye doped sol–gel materials and MPc offers an excellent opportunity to characterize dimers from monomers because of their identified absorption bands, we studied the dimerization of different kinds of MPc doped silica composites using electronic absorption spectra. Changes in the absorption spectra were correlated with various stages of the sol–gel process. The results show that in the composite MPc molecules concurrence in forms of monomer and dimer, and dimerization is bad during the latter stages of drying because of the rapid decrease of remaining solvent and its ethanol/water ratio. To overcome this problem, a kind of dissociating agent Cremophor EL is added in order to protect the Zinc tetrasulfo-phthalocyanine molecules from dimerization. In the other hand, a newly developed in situ synthesis technique was successfully introduced to synthesize MPc during the sol–gel process. It is found that the in situ synthesized MPc only exist in the form of monomer in the composites.