Synthesis, structural characterization, photophysical properties, DFT and TDDFT calculations, and photoredox catalysis studies of 2,9-di(aryl)-1,10-phenanthroline copper (I) complexes
The synthesis, characterization, photophysical properties, theoretical calculations, and catalytic studies of 2,9-di(aryl)-1,10-phenanthroline copper (I) complexes are described. Specifically, this study made use of di(aryl)-1,10-phenanthroline ligands including 2,9-di(4-methoxyphenyl)-1,10-phenanthroline (1), 2,9-di(4-hydroxyphenyl)-1,10-phenanthroline (2), 2,9-di(4-methoxy-3-methylphenyl)-1,10-phenanthroline (3), and 2,9-di(4-hydroxy-3-methylphenyl)-1,10-phenanthroline (4). The 2:1 ligand-to-metal complexes, as PF6- salts, i.e., ([Cuˑ(1)2¬]PF6, [Cuˑ(2)2¬]PF6, [Cuˑ(3)2-]PF6, and [Cuˑ(4)2¬]PF6) have been isolated and characterized. The structures of ligands 1 and 2 and complexes [Cuˑ(1)2¬]PF6 and [Cuˑ(3)2¬]PF6 have been determined by single-crystal X-ray analysis. The photoredox catalytic activity of these copper (I) complexes was investigated in an atom-transfer radical addition (ATRA) reaction and the results showed fairly efficient activity. In order to better understand the observed catalytic activity, photophysical emission and absorption studies, and DFT calculations were also performed. In light of these results, a mechanism for the ATRA photoredox catalytic cycle has been proposed.