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Photocytotoxicity of Oligothienyl‐Functionalized Chelates That Sensitize Ln III Luminescence and Generate 1 O 2
Author(s) -
Johnson Katherine R.,
Lombardi Vincent C.,
BettencourtDias Ana
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001568
Subject(s) - luminescence , lanthanide , tris , chemistry , nuclear chemistry , chelation , ethanol , singlet oxygen , irradiation , ion , analytical chemistry (journal) , crystallography , photochemistry , oxygen , materials science , inorganic chemistry , biochemistry , physics , optoelectronics , organic chemistry , chromatography , nuclear physics
Three new compounds containing a heptadentate lanthanide (Ln III ) ion chelator functionalized with oligothiophenes, n Thept(COOH) 4 ( n =1, 2, or 3), were isolated. Their Ln III complexes not only display the characteristic metal‐centered emission in the visible or near‐infrared (NIR) but also generate singlet oxygen ( 1 O 2 ). Luminescence efficiencies ( ϕ Ln ) for [Eu 1 Thept(COO) 4 ] − and [Eu 2 Thept(COO) 4 ] − are ϕ Eu =3 % and 0.5 % in TRIS buffer and 33 % and 3 % in 95 % ethanol, respectively. 3 Thept(COO) 4 4− does not sensitize Eu III emission due to its low‐lying triplet state. Near infra‐red (NIR) luminescence is observed for all NIR‐emitting Ln III and ligands with efficiencies of ϕ Yb =0.002 %, 0.005 % and 0.04 % for [Yb n Thept(COO) 4 ] − ( n =1, 2, or 3), and ϕ Nd =0.0007 %, 0.002 % and 0.02 % for [Nd n Thept(COO) 4 ] − ( n =1, 2, or 3) in TRIS buffer. In 95 % ethanol, quantum yields of NIR luminescence increase and are ϕ Yb =0.5 %, 0.31 % and 0.05 % for [Yb n Thept(COO) 4 ] − ( n =1, 2, or 3), and ϕ Nd =0.40 %, 0.45 % and 0.12 % for [Nd n Thept(COO) 4 ] − ( n =1, 2, or 3). All complexes are capable of generating 1 O 2 in 95 % ethanol with ϕ 1Ο2 efficiencies which range from 2 % to 29 %. These complexes are toxic to HeLa cells when irradiated with UV light ( λ exc =365 nm) for two minutes. IC 50 values for the Ln III complexes are in the range 15.2–16.2 μ m ; the most potent compound is [Nd 2 Thept(COO) 4 ] − . The cell death mechanisms are further explored using an Annexin V—propidium iodide assay which suggests that cell death occurs through both apoptosis and necrosis.