Modulation of the Excited States of Ruthenium(II)-perylene Dyad to Access Near-IR Luminescence, Long-Lived Perylene Triplet State and Singlet Oxygen Photosensitization.

Herein, we present a novel ruthenium(II)-perylene dyad (RuPDI-Py) that combines the photophysical properties of pyrrolidine-substituted perylene diimide (PDI-Py) and the ruthenium(II) polypyridine complex [Ru(phen)]. A comprehensive study of excited-state dynamics was carried out using time-resolved and steady-state methods in a dimethyl sulfoxide solution. The RuPDI-Py dyad demonstrated excitation wavelength-dependent photophysical behavior. Upon photoexcitation above 600 nm, the dyad exclusively exhibits the near-infrared (NIR) fluorescence of the PDI-Py state at 785 nm (τ = 1.50 ns). In contrast, upon photoexcitation between 350 and 450 nm, the dyad also exhibits a photoinduced electron transfer from the {[Ru(phen)]} moiety to PDI-Py, generating the charge-separated intermediate state {Ru(III)-(PDI-Py)} (4 μs). This state subsequently decays to the long-lived triplet excited state PDI-Py (36 μs), which is able to sensitize singlet oxygen (O). Overall, tuning O photoactivation or NIR fluorescence makes RuPDI-Py a promising candidate for using absorbed light energy to perform the desired functions in theranostic applications.