Synthesis and properties of cyclophosphazenes appended with covalently linked porphyrin–ferrocene conjugates

Abstract

Cyclotriphosphazene and cyclotetraphosphazene appended with six and eight covalently linked porphyrin–ferrocene conjugates respectively were synthesized by treating N₃P₃Cl₆ and N₄P₄Cl₈ with appropriate equivalents of ferrocene linked porphyrin containing meso-hydroxyphenyl group in THF in the presence of Cs₂CO₃ followed by column chromatographic purification. NMR and absorption studies indicated a weak interaction between adjacent porphyrin–ferrocene conjugates. Electrochemical studies supported electrochemical equivalence of ferrocenyl and porphyrinyl moieties in these multi-porphyrin–ferrocene conjugate assemblies. The fluorescence studies showed significant quenching of porphyrin fluorescence due to photo-induced electron transfer from ferrocene to singlet state of porphyrin unit in these assemblies.