Synthesis of alkyne-linked porphyrin complexes for organic nanosensor

Abstract

A series of meso-alkyne-linked porphyrin metal complexes has been synthesized by Sonogashira coupling reactions in satisfactory yield (11-88%). The mesityl groups were chosen to use as side chains in order to improve the solubility, whereas the alkynyl groups were linked at meso-positions to extend the π-conjugated system of porphyrins. All synthesized porphyrins were characterized by 1H NMR spectroscopy and MALDI-TOF mass spectrometry. Their photophysical properties were also investigated by UV-visible spectroscopy and fluorescence spectroscopy. It has been demonstrated that central metal ions as well as meso-substituents, especially alkyne linkers, affected the absorption and emission spectra of porphyrins. The spectroscopic data revealed that alkyne-linked porphyrins exhibited higher π-conjugation compared to porphyrin building blocks resulting in the red shifts in both absorption and emission spectra. Coordination properties of synthesized porphyrins have been preliminarily studied by 1H NMR, UV-visible, and fluorescence spectroscopic titration with pyridine as axial ligand. The 1H NMR titration results indicated the 1:1 complexation of porphyrin metal complexes with pyridine. In addition, the significant red shifts in absorption spectra and decreasing of the fluorescence intensity upon an addition of pyridine also supported the formation of porphyrin-pyridine complexes.