Efficient and selective singlet oxygen sensitized NIR luminescence of a neodymium(III) complex and its application in biological imaging

A responsive neodymium NIR emission (⁴F_3/2→⁴I_{11/2, 9/2}) was recorded upon binding with singlet oxygen (K_B=1.79×10⁶ M⁻¹) via the anthracene moiety. The motif ytterbium analog served as a negative control with no significant NIR enhancement/quenching with the addition of the same amount of singlet oxygen. Our complex was also found to react with ¹O₂ generated by a known photosensitizer TMPyP inside HeLa cells without inducing cell death and display no significant cytotoxicity. - Highlights: • A turn-on NIR-emissive ¹O₂ probe has been synthesized for potential biological applications. • It has a binding constant of 1.9×10⁶ M⁻¹ and the emission intensity has a 5-fold increase upon binding. • The probe was also found to quench singlet oxygen in vitro generated by known photosensitizer TMPyP.