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

Abstract

Biscyclometalated Ir 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≈4.46×10 m cm and 3.38×10 m cm at 517 nm and 594 nm, respectively), higher moderate fluorescence emission (φ ≈0.08 and 0.22 at 528 nm and 652 nm, respectively) and, in particular, more efficient singlet oxygen generation upon visible-light irradiation (φ ≈0.86 and 0.59, respectively) than that exhibited by Ir-3 (φ ≈0.51, but only under UV light). Phosphorescence emission, nanosecond time-resolved transient absorption, and DFT calculations suggest that BODIPY-localized long-lived IL 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.

Exploring BODIPY Derivatives as Singlet Oxygen Photosensitizers for PDT

“…To elucidate the relevance of the involved acac‐BODIPY moiety in the efficiency as a PS of these novel dyes, a related iridium complex bearing the same biscyclometalated Ir(III) unit and meso ‐substituted BODIPY moiety, but connected through a large, dipyridophenazine π‐conjugated ligand ( 22 in Fig. 8), was also synthesized and studied (93).…”

Towards Novel Photodynamic Anticancer Agents Generating Superoxide Anion Radicals: A Cyclometalated IrIIIComplex Conjugated to a Far‐Red Emitting Coumarin

“…[1] Examples of this approach include boron-dipyrromethene (BODIPY) fluorophores [5] and their conjugation to cyclometalated iridium(III) complexes. [6] Conventional coumarins have also been conjugated to Ir III complexes,e ither to increase singlet oxygen quantum yield [7] or to target mitochondria. [8] Fluorophores based on small organic molecules have become essential daily tools in bioimaging applications,both in basic research and in diagnoses and therapy.…”

Photocytotoxic Copper(II) Complexes with Schiff‐Base Scaffolds for Photodynamic Therapy

“…[11][12][13][14] Furthermore, comparedt op latinum and ruthenium complexes,copper complexes have demonstratedgood antitumor activity with fewer side effects. [20][21][22][23][24] In as imilar fashion, metal complexes with Schiff-base scaffolds have been effectively applied as antibacterial chemotherapeutic moieties in medicine. [20][21][22][23][24] In as imilar fashion, metal complexes with Schiff-base scaffolds have been effectively applied as antibacterial chemotherapeutic moieties in medicine.…”

“…[15][16][17][18][19] Moreover,av ariety of pyridine-ligand-based complexes have exhibited high reactivity toward DNA cleavage and cell apoptosis. [20][21][22][23][24] In as imilar fashion, metal complexes with Schiff-base scaffolds have been effectively applied as antibacterial chemotherapeutic moieties in medicine. [25,26] The chemotherapeutic effect of Cu II -containing Schiff-base complexes may be enhanced by tuningt he electronic properties of the metal centero rt he ligandst hrough coordination.…”