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Photophysical and Photobiological Properties of Dinuclear Iridium(III) Bis-tridentate Complexes
journal contribution
posted on 2018-08-09, 18:51 authored by Bingqing Liu, Susan Monro, Levi Lystrom, Colin G. Cameron, Katsuya Colón, Huimin Yin, Svetlana Kilina, Sherri A. McFarland, Wenfang SunA series
of cationic dinuclear iridium(III) complexes (Ir1–Ir5) bearing terpyridine-capped fluorenyl bridging
ligands and different polypyridyl or cyclometalating terminal tridentate
ligands were synthesized, characterized, and evaluated for their photophysical
and photobiological activities. The influence of the bridging and
terminal ligands on the photophysical properties of the complexes
was investigated by UV–vis absorption, emission, and transient
absorption spectroscopy and simulated by TDDFT calculations. All of
the complexes displayed strong bridging-ligand localized visible 1π,π* absorption and red- or near-infrared phosphorescence
as well as broad triplet excited-state absorption across both visible
and NIR wavelengths. These triplet states were assigned as predominantly 3π,π* for Ir1 (τ = 3.1 μs)
and Ir4 (τ = 48 μs) and 3CT (charge transfer) for Ir2, Ir3, and Ir5 (τ = 1.7–2.7 μs). Complexes Ir1–Ir5 acted as in vitro photodynamic
therapy (PDT) agents toward human SK-MEL-28 melanoma cells when activated
with visible light, with submicromolar photocytotoxicity and phototherapeutic
indices ranging from 20 to almost 300. The in vitro PDT effects with
visible light did not correlate with singlet oxygen (1O2) quantum yields or DNA photocleaving capacity probed under
cell-free conditions. All of the Ir(III) complexes phosphoresced brightly
when associated with compromised cells (with or without light treatment)
and exhibited photoactivated cellular uptake, highlighting the theranostic
potential of this new class of Ir(III) complex photosensitizers.
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triplet excited-state absorptioncharge transferSK-MEL -28 melanoma cellsDNA photocleaving capacityIr 3Ir 23 CTabsorption spectroscopyquantum yieldssinglet oxygenUVsubmicromolar photocytotoxicitynear-infrared phosphorescencephotophysical propertiesTDDFT calculationsPDT effectsterpyridine-capped fluorenyl1 O 23.1 μNIR wavelengthsPhotobiological Propertieslight treatmentcyclometalating terminal tridentate ligandsphototherapeutic indicesphotodynamic therapycomplexphotobiological activitiestriplet states48 μterminal ligands
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