AcetylacetonateBODIPY‐Biscyclometalated Iridium(III) Complexes: Effective Strategy towards Smarter Fluorescent Photosensitizer Agents

• Published in: Chemistry : a European journal 2017-07, Vol.23 (42), p.10139-10147
• Main Authors: Palao, Eduardo, Sola‐Llano, Rebeca, Tabero, Andrea, Manzano, Hegoi, Agarrabeitia, Antonia R., Villanueva, Angeles, López‐Arbeloa, Iñigo, Martínez‐Martínez, Virginia, Ortiz, Maria J.
• Format: Article
• Language: English
• Subjects: Absorption; BODIPY; Boron; Boron Compounds - chemistry; Cell Survival - drug effects; Cell Survival - radiation effects; Chelation; Chemistry; Coordination Complexes - chemical synthesis; Coordination Complexes - chemistry; Coordination Complexes - toxicity; Cores; Emission; Fluorescence; Fluorescent Dyes - chemistry; fluorescent probes; HeLa Cells; Humans; In vitro methods and tests; Iridium; Iridium - chemistry; Iridium compounds; iridium(III) complexes; Irradiation; Light irradiation; Microscopy, Fluorescence; Phosphorescence; Photochemotherapy; Photodynamic therapy; Photosensitizing Agents - chemical synthesis; Photosensitizing Agents - chemistry; Photosensitizing Agents - toxicity; Quantum Theory; Singlet oxygen; Singlet Oxygen - chemistry; Singlet Oxygen - metabolism; Ultraviolet radiation; Ultraviolet Rays
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201701347

Biscyclometalated IrIII complexes involving boron‐dipyrromethene (BODIPY)‐based ancillary ligands, where the BODIPY unit is grafted to different chelating cores (acetylacetonate for Ir‐1 and Ir‐2, and bipyridine for Ir‐3) by the BODIPY meso position, have been synthesized and characterized. Complexes with the BODIPY moiety directly grafted to acetylacetonate (Ir‐1 and Ir‐2) exhibit higher absorption coefficients (ϵ≈4.46×104 m−1 cm−1 and 3.38×104 m−1 cm−1 at 517 nm and 594 nm, respectively), higher moderate fluorescence emission (φfl≈0.08 and 0.22 at 528 nm and 652 nm, respectively) and, in particular, more efficient singlet oxygen generation upon visible‐light irradiation (φΔ≈0.86 and 0.59, respectively) than that exhibited by Ir‐3 (φΔ≈0.51, but only under UV light). Phosphorescence emission, nanosecond time‐resolved transient absorption, and DFT calculations suggest that BODIPY‐localized long‐lived 3IL states are populated for Ir‐1 and Ir‐2. In vitro photodynamic therapy (PDT) activity studied for Ir‐1 and Ir‐2 in HeLa cells shows that such complexes are efficiently internalized into the cells, exhibiting low dark‐ and high photocytoxicity, even at significantly low complex concentration, making them potentially suitable as theranostic agents. Kill and cure: New boron‐dipyrromethene (BODIPY)–iridium(III) complexes, synthesized by a straightforward synthetic approach, exhibit efficient singlet oxygen generation, low dark and high photocytoxicity under visible radiation even at low photosensitizer concentrations.