Increasing the triplet lifetime and extending the ground-state absorption of biscyclometalated Ir(iii ) complexes for reverse saturable absorption and photodynamic therapy applications
| Autor: | Chengzhe Wang, Levi Lystrom, Marc Hetu, Huimin Yin, Svetlana Kilina, Wenfang Sun, Sherri A. McFarland |
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| Rok vydání: | 2016 |
| Předmět: | |
| Zdroj: | Dalton Transactions. 45:16366-16378 |
| ISSN: | 1477-9234 1477-9226 |
| Popis: | The synthesis, photophysics, reverse saturable absorption, and photodynamic therapeutic effect of six cationic biscyclometalated Ir(III) complexes (1–6) with extended π-conjugation on the diimine ligand and/or the cyclometalating ligands are reported in this paper. All complexes possess ligand-localized 1π,π* absorption bands below 400 nm and charge-transfer absorption bands above 400 nm. They are all emissive in the 500–800 nm range in deoxygenated solutions at room temperature. All complexes exhibit strong and broad triplet excited-state absorption at 430–800 nm, and thus strong reverse saturable absorption for ns laser pulses at 532 nm. Complexes 1–4 are strong reverse saturable absorbers at 532 nm, while complex 6 could be a good candidate as a broadband reverse saturable absorber at 500–850 nm. The degree of π-conjugation of the diimine ligand mainly influences the 1π,π* transitions in their UV-vis absorption spectra, while the degree of π-conjugation of the cyclometalating ligand primarily affects the nature and energies of the lowest singlet and emitting triplet excited states. However, the lowest-energy triplet excited states for complexes 3–6 that contain the same benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine (dppn) diimine ligand but different cyclometalating ligands remain the same as the dppn ligand-localized 3π,π* state, which gives rise to the long-lived, strong excited-state absorption in the visible to the near-IR region. All of the complexes exhibit a photodynamic therapeutic effect upon visible or red light activation, with complex 6 possessing the largest phototherapeutic index reported to date (>400) for an Ir(III) complex. Interactions with biological targets such as DNA suggest that a novel mechanism of action may be at play for the photosensitizing effect. These Ir(III) complexes also produce strong intracellular luminescence that highlights their potential as theranostic agents. |
| Databáze: | OpenAIRE |
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