Synthesis, characterization, energy transfer and photophysical properties of ethynyl bridge linked porphyrin–naphthalimide pentamer and its metal complexes

• A novel naphthalimide-functionized porphyrin TANPH2 has been synthesized.
• TANPH2 and TANPZn can emit intense red light with high fluorescent quantum yields.
• The photo-excitation energy transfer occurred from naphthalimide to porphyrin core.
• TANPH2 and TANPZn can act as efficient light-harvesting antennae.

A novel ethynyl bridge linked naphthalimide-functionized porphyrin TANPH2 has been synthesized by a combination of Sonogashira coupling and Gonsalves and Pereira nitrobenzene reaction, and the corresponding metal (Zn2+ and Cu2+) complexes TANPZn and TANPCu were synthesized. The structures of these compounds were characterized by 1H and 13C 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. Energy transfer studies have revealed that the excitation energy transfer occurred from the naphthalimide units to the porphyrin core. By the introduction of ethynyl bridges between the peripheral naphthalimide arms and the porphyrin core, TANPH2 and TANPZn can emit intense red light with high fluorescent quantum yields.

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