Ru(II)
Dyads Derived from 2‑(1-Pyrenyl)‑1<i>H</i>‑imidazo[4,5‑<i>f</i>][1,10]phenanthroline:
Versatile Photosensitizers for Photodynamic Applications
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Abstract
Combining
the best attributes of organic photosensitizers with
those of coordination complexes is an elegant way to achieve prolonged
excited state lifetimes in Ru(II) dyads. Not only do their reduced
radiative and nonradiative rates provide ample time for photosensitization
of reactive oxygen species at low oxygen tension but they also harness
the unique properties of <sup>3</sup>IL states that can act as discrete
units or in concert with <sup>3</sup>MLCT states. The imidazo[4,5-<i>f</i>][1,10]phenanthroline framework provides a convenient tether
for linking π-expansive ligands such as pyrene to a Ru(II) scaffold,
and the stabilizing coligands can fine-tune the chemical and biological
properties of these bichromophoric systems. The resulting dyads described
in this study exhibited nanomolar light cytotoxicities against cancer
cells with photocytotoxicity indices exceeding 400 for some coligands
employed. This potency extended to bacteria, where concentrations
as low as 10 nM destroyed 75% of a bacterial population. Notably,
these dyads remained extremely active against biofilm with light photocytotoxicities
against these more resistant bacterial populations in the 10–100
nM regime. The results from this study demonstrate the versatility
of these highly potent photosensitizers in destroying both cancer
and bacterial cells and expand the scope of compounds that utilize
low-lying <sup>3</sup>IL states for photobiological applications