¹O₂ Generating Luminescent Lanthanide Complexes with 1,8-Naphthalimide-Based Sensitizers

Lanthanide ion (Ln^III) complexes with two new 1,8-naphthalimide-based ligands, Nap-dpe and Nap-cbx, were isolated, and their photophysical properties were explored. Upon excitation at 335 nm, Nap-dpe and Nap-cbx sensitize visible and near-infrared emitting Ln^III ions (Ln^III = Eu^III, Nd^III, and Yb^III) and generate singlet oxygen (¹O₂). The quantum yields of Eu^III luminescence for [Eu(Nap-cbx)₃]³⁺ and [Eu(Nap-dpe)₃]³⁺ are 16.7% and 8.3%, respectively, with ¹O₂ generation efficiencies of 41% and 59%, respectively. The efficiencies of ¹O₂ generation for the NIR emitting complexes [Ln(Nap-dpe)₃]³⁺ are 59% and 56%, respectively, and those for [Ln(Nap-cbx)₃]³⁺ (Ln^III = Nd^III, Yb^III) are 64% and 61%, respectively. In an oxygen-free environment, the quantum yields of Eu^III luminescence for [Eu(Nap-cbx)₃]³⁺ and [Eu(Nap-dpe)₃]³⁺ increase to 20% and 18%, respectively.