Homoleptic Lanthanide Complexes Containing a Redox-Active Ligand and the Investigation of Their Electronic and Photophysical Properties

Herein, we describe the preparation, characterization and photophysical properties of neutral lanthanide complexes containing a redox-active ligand 1-(2-pyridylazo)-2-phenanthrol (papl). The complexes likely share similar structural features and bear the formulation Ln(papl)3 (Ln(III) = Gd, Dy, Tb), which is supported by electrospray ionization mass spectrometry, CHN analysis, FT-IR and UV–Vis spectroscopy. The synthesis and structural properties of a related complex, Ho(qapl)3 (where qapl = 10-(8-quinolylazo)-9-phenanthrol), is also reported. The complexes feature ligand-centered redox activity, similar to other reported transition metal complexes with papl. Variable temperature magnetic susceptibility measurements (DC and AC) suggest typical free-ion magnetism without any slow-relaxation dynamics. The photophysical properties of the ligand and complexes were investigated and the results of emission spectroscopy indicate ligand-centered processes.