Synthesis, spectral and electrochemical properties of cyclotriphosphazene appended with six metalloporphyrins

The metal derivatives (CoII, NiII, CuII, ZnII and SnIV) of hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assembly on cyclotriphosphazene ring with the appropriate metal salt under standard metallation conditions. The complete metallation of all six porphyrin units in hexaporphyrin assembly required 10–12 h reflux as judged by the absorption spectroscopy. The metal derivatives were confirmed by molecular ion peak in mass spectra for all compounds. 31P and 1H NMR spectra for Ni(II), Zn(II) and Sn(IV) derivatives and ESR spectra for Cu(II) derivative also confirmed the complete metallation of all six porphyrin units. The hexametalloporphyrin assemblies are freely soluble in common organic solvents. The spectral, electrochemical and fluorescence studies indicate that the six porphyrin units in assemblies interact very weakly and retain their individual characteristic features in the ground and excited states.