Cyclotriphosphazene ring as a platform for multiporphyrin assemblies

Abstract

Rings around a ring: The synthesis, characterization, material properties and biological studies of novel hexakis porphyrinato cyclotriphosphazene systems (see scheme) and their metal derivatives are described. A simple method has been employed to synthesize a cyclotriphosphazene appended with six porphyrins. The reaction of one equivalent of hexachlorocyclotriphosphazene with six equivalents of 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl)porphyrin or -21-thiaporphyrin in tetrahydrofuran in the presence of cesium carbonate, followed by simple column-chromatography purification, afforded the hexaporphyrinato cyclotriphosphazene systems as the single products in 80–90 % yields. The metal (II) derivatives (Cu^II, Zn^II) of the hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assemblies with the appropriate metal salts under standard metallation conditions. The compounds are freely soluble in common organic solvents and were characterized by mass spectrometry, NMR, absorption and fluorescence spectroscopy, and electrochemical techniques. Material studies carried out by using fluorescence microscopy, SEM and AFM techniques showed that the hexaporphyrinato cyclotriphosphazene systems form ringlike architectures. Preliminary biological studies indicate that the hexacopper (II) porphyrin assembly can be used as an artificial nuclease.