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 (O-1(2)). 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 O-1(2) generation efficiencies of 41% and 59%, respectively. The efficiencies of O-1(2) 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.