Synthesis and characterization of Cu(II), Ni(II), and Fe(III) complexes of 5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin

Abstract

We have synthesized three complexes of 5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin (ENTPP), [Cu(ENTPP)], [Ni(ENTPP), and [Fe(ENTPP)Cl]. X-ray crystallography reveals that copper and nickel species are four-coordinate, while the iron complex is five-coordinate. The porphyrin in all the three species maintains similar conformations, in which rotational hindrance makes the ester group at the 8-position of naphthyl lie above the porphyrin plane leading to axial chirality in the single molecule. However, only chiral crystals of [Cu(ENTPP)] were obtained by spontaneous resolution upon crystallization, while [Ni(ENTPP) and [Fe(ENTPP)Cl] were obtained as achiral crystals of racemic compounds. CD spectra have also confirmed the chirality of the crystalline samples. The origin of CD signals has also been discussed.

Keywords:

• Chiral porphyrin
• Naphthyl
• Spontaneous resolution
• Crystal structure

Acknowledgments

This work was supported by the Natural Science Foundation of China (Nos. 20971093 and 21271133) and the Priority Academic Program Development of Jiangsu Higher Education Institutions.