Synthesis of novel unsymmetrically substituted push-pull phthalocyanines

The synthesis and characterization of novel non-centrosymmetrically push-pull substituted metal-free phthalocyanines 3-9 are described. The compounds have different donor (dialkoxy, tert-butyl, methyl, p-tolylthio) and/or attractor (p-tolylsulfinyl, p-tolylsulfonyl, nitro) functional groups, are soluble in organic solvents, and are especially designed to study their second- and third-order nonlinear optical properties. Compounds 7-9 are mixtures of the four corresponding regioisomers. For preparing the unsymmetrical phthalocyanines 7-9, the effectiveness of the subphthalocyanine route, using different substituted diiminoisoindolines as reagents, has been tested. Furthermore, a comparison between this method versus the statistical one has been done. The results obtained show that the ring enlargement reaction of subphthalocyanines to obtain unsymmetrically substituted phthalocyanines is not a selective reaction but a multistep process, which depends dramatically on the nature of the substituents on the subphthalocyanines, the reactivity of the iminoisoindoline, the solvent, and other factors that limit its general synthetic utility. Preliminary data of the experimental second-order hyperpolarizabilities of compounds 3-9 are also given.