A Synthetic Approach to Asymmetric Phthalocyanines with Peripheral Metal‐Binding Sites
A phthalonitrile derivative 1, functionalized with two pyridyl groups, undergoes a cyclotetramerization reaction to afford the symmetric metal-free phthalocyanine 2 with peripheral metal-binding sites. In view of its insufficient solubility in organic solvents, a synthetic route to asymmetric peripherally octasubstituted Pcs, which contain a combination of 2,3-di(2-pyridyl)pyrazino and p-pentylphenoxy or p-(tert-butyl)phenoxy substituent groups, has been developed. The compounds 5–9 were synthesized by a statistical condensation reaction between two different phthalonitriles, and remarkably, all of them have been isolated and characterized as single compounds. For structural characterization, an X-ray study of the asymmetric Zn phthalocyanine 11 is given. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)