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

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 multiporphyrin-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. (C) 2012 Elsevier B. V. All rights reserved