Synthesis, characterization and properties of covalently linked porphyrin-naphthalimide pentamer and its metal complexes

A novel porphyrin naphthalimide pentamer 5 was synthesized by linking four light-harvesting naphthalimide units to a central porphyrin, via ether bridges. The corresponding metal (Zn2+, Cu2+, Mn2+, Fe3+, Co2+) complexes 6a-6e were obtained under different reaction conditions. The structures of these compounds were characterized by H-1 and C-13 NMR spectra, FT-IR, MALDI-TOF-MS and elemental analysis. The photophysical properties have been investigated by UV-Vis absorption and steady-state fluorescence spectroscopy. It is found that the excitation energy transfer occurs from the naphthalimide units to the porphyrin core, and that the free base porphyrin 5 and Zn porphyrin 6a can emit intense red light. Additionally, the electrochemical properties of compounds 5 and 6a-6e were also investigated by cyclic voltammetry. (C) 2014 Published by Elsevier B.V.