Wavelength‐Dependent Singlet Oxygen Generation in Luminescent Lanthanide Complexes with a Pyridine‐Bis(Carboxamide)‐Terthiophene Sensitizer

Abstract

Lanthanide ion (LnIII) complexes, [Ln(3Tcbx)2]3+ (LnIII=YbIII, NdIII, ErIII) are isolated with a new pyridine‐bis(carboxamide)‐based ligand with a 2,2′:5′,2′′‐terthiophene pendant (3TCbx), and their resulting photophysical properties are explored. Upon excitation of the complexes at 490 nm, only LnIII emission is observed with efficiencies of 0.29 % at 976 nm for LnIII=YbIII and 0.16 % at 1053 nm for LnIII=NdIII. ErIII emission is observed but weak. Upon excitation at 400 nm, concurrent 1O2 formation is seen, with efficiencies of 11 % for the YbIII and NdIII complexes and 13 % for the ErIII complex. Owing to the concurrent generation of 1O2, as expected, the efficiency of metal‐centered emission decreases to 0.02 % for YbIII and 0.05 % for NdIII. The ability to control 1O2 generation through the excitation wavelength indicates that the incorporation of 2,2′:5′,2′′‐terthiophene results in access to multiple sensitization pathways. These energy pathways are unraveled through transient absorption spectroscopy.

Photocytotoxicity of Thiophene- and Bithiophene-Dipicolinato Luminescent Lanthanide Complexes

“…Although we do not anticipate leaching of the metal ion from these complexes, control experiments using the LnCl 3 salts were conducted and confirmed that the free metal ions are not cytotoxic (Figures S34−S38), as previously observed. 33 ) for [Ln(nTdpa) 3 ] 3− (n = 1 or 2) in 95% Ethanol at 25.0 ± 0.1 The combined data suggest that these photosensitizers are potential photodynamic therapeutics with low dark toxicity. The cell death mechanism was studied by flow cytometry of HeLa cells stained with Annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) after incubating the cells with 12.5 μM of the 2Tdpa 2− -based compounds in the dark and after a short irradiation period of 5 min.…”

“…These complexes are not water-soluble and are thus not viable for imaging and therapy applications in biological systems. More recently, we described a family of oligothiophene-based sensitizers of Ln III emission, which show wavelength-dependent 1 O 2 generation , but are also not water-soluble. Another series of oligothiophene-based ligands that were water-soluble were studied for their cytotoxicity toward HeLa cells .…”

“…Oligothiophenes are naturally occurring plant pigments known for their ability to generate 1 O 2 with high . Because of this property, oligothiophenes and thienyl-derivatized compounds are reported to have applications as antiviral, anticancer, and antifungal agents. − Thus, thiophene-based functional groups are promising because of their ability to enhance ISC , and efficiently generate 1 O 2 and of their interesting photophysical properties. ,,− …”

Metal‐Coordinated Supramolecular Self‐Assemblies for Cancer Theranostics

“…Some early reports focus on the construction of RE‐coordinated nanostructures with different compositions, morphologies, and applications. [ 146 ] Subsequently, the development of nanomaterials for bioimaging [ 85 , 86 , 90 , 147 ] and cancer theranostics [ 87 , 144 , 145 , 148 ] attracted increasing research interest. Jin et al reported an Nd integrated supramolecular polymeric nanoassembly to deliver siRNA and DOX for tumor therapy.…”

New Approach in the Application of Conjugated Polymers: The Light-Activated Source of Versatile Singlet Oxygen Molecule

“…Moreover, it has been shown that the energy levels of the S n and T n states, and thus the ISC process [35], can be optimized by increasing the number of conjugated units, which is the basis of so-called "polymerization-enhanced photosensitization" concept [16,36,37]. Conjugated oligomers/polymers can be applied in the photosensitization of 1 O 2 either acting as photosensitizer itself or acting as the light-harvesting antennas or backbone to other PS molecules (e.g., dyes, fullerenes) [34,38,39]. In this review paper, the examples of both types of CP-based photosensitizers used in the medical applications, fine chemical synthesis or wastewater treatment-will be discussed.…”