Ru(II) Dyads Derived from 2-(1-Pyrenyl)-1H-imidazo[4,5-f][1,10]phenanthroline: Versatile Photosensitizers for Photodynamic Applications

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 (3)IL states that can act as discrete units or in concert with (3)MLCT states. The imidazo[4,5-f][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 (3)IL states for photobiological applications.

Photophysics of Ru(II) Dyads Derived from Pyrenyl-Substitued Imidazo[4,5-f][1,10]phenanthroline Ligands

“…24 Samples were excited with 10-ps pulses centered at 410 nm. For transient absorption measurements, the probe wavelength was scanned between 380 and 800 nm in steps of 10 nm, and a quantitative data analysis was based on a global fit of the data obtained at all probe-wavelengths.…”

“…24 These complexes belong to a class of compounds that we call metal-organic dyads, and their unusual PDT effects stem from low-energy 3 IL states contributed by organic chromophores.…”

“…24 These complexes proved to be sensitive to trace amounts of oxygen (K SV as low as 0.2393 Torr -1 ) 27 , making them attractive PSs for targeting hypoxic tumours with PDT. There is much interest in the design of oxygen-independent PSs for PDT given that the most aggressive and drugresistant malignancies are hypoxic.…”

Ruthenium Imidazophenanthrolinium Complexes with Prolonged Excited‐State Lifetimes

“…[37] Emission Lifetimes: The emission lifetimes were determined by using a ns transient-absorption setup in 90°geometry. [58] The pump was delivered by a Continuum Surelite OPO Plus oscillator pumped by a Continuum Surelite Nd:YAG laser (pulse duration 5 ns, pulse-to-pulse repetition rate 10 Hz), and the probe light was a 75 W xenon arc lamp. Spherical concave mirrors were used to focus the probe light onto the sample and to refocus the light on the entrance slit of a monochromator (Acton, Princeton Instruments).…”

Photocleavage of DNA and adenine–thymine inclined binding by a novel ruthenium(II) complex with 3,4-dibromo-imidazo[4,5-f][1,10]phenanthroline ligand

“…These results implied the potential applications of [Ru(phen) 2 (ODBIP)] 2+ as PDT agents. The up-to-date studies on low-energy and long-lived triplet intraligand ( 3 IL) excited states (with microsecond lifetime) of ruthenium(II)-based transition metal complexes provided an explanation for the DNA photodamage by multi-wavelength light [22,23]. Further experiments will be conducted to study the effects of the mixed wave lights.…”