Dual‐Sensitized Luminescent Europium(ΙΙΙ) and Terbium(ΙΙΙ) Complexes as Bioimaging and Light‐Responsive Therapeutic Agents |
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| Authors: | Srikanth Dasari Swati Singh Prof?Dr Sri Sivakumar Prof?Dr Ashis K Patra |
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| Affiliation: | 1. Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India;2. Department of Chemical Engineering and Centre for Environmental Science and Engineering, Indian Institute of Technology Kanpur, Kanpur, India |
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| Abstract: | Dual‐photosensitized stable EuΙΙΙ and TbΙΙΙ complexes, namely Eu(dpq)(tfnb)3] ( 1 ) and Tb(dpq)(tfnb)3] ( 2 ), in which dpq=dipyrido3,2‐d:2′,3′‐f]quinoxaline and Htfnb=4,4,4‐trifluoro‐1‐(2‐napthyl)‐1,3‐butanedione, were designed as bioimaging and light‐responsive therapeutic agents. Their X‐ray structures, photophysical properties, biological interactions, photoinduced DNA damage, photocytotoxicity, and cellular uptake properties were studied. Discrete mononuclear complexes adopt an eight‐coordinated {LnN2O6} distorted square antiprism geometry with bidentate N,N‐donor dpq and O,O‐donor tfnb ligands. The designed probes have the advantage of dual‐sensitizing antennae (dpq, Htfnb) to modulate their desirable optical properties for cellular imaging and light‐responsive intracellular damage. The remarkable photostability, absence of inner‐sphere water (q<1), and longer excited‐state lifetimes of the complexes make them suitable as cellular‐imaging probes. The dpq 3T state is well located energetically to allow efficient energy transfer (ET) to the emissive 5D0 and 5D4 states of EuΙΙΙ and TbΙΙΙ. This leads to higher quantum yields (φ=0.15–0.20) in aqueous media and makes these compounds suitable cellular‐imaging probes. The complexes display significant binding ability toward DNA and bovine serum albumin (K≈105 m ?1). They effectively cleave supercoiled DNA to its nicked circular form at λ=365 nm through photoredox pathways. The cellular internalization studies showed cytosolic and nuclear localization. The remarkable photocytotoxicity of these probes offers a strategy towards developing photoresponsive LnΙΙΙ probes as cellular‐imaging and phototherapeutic agents. |
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| Keywords: | cellular imaging europium lanthanides luminescence terbium |
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