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Photodynamic Applications of New Imidazo[4,5‐f][1,10]phenanthroline Oxidovanadium(IV) Complexes: Synthesis, Photochemical, and Cytotoxic Evaluation
Author(s) -
Sanasam Bandana,
Raza Md K.,
Musib Dulal,
Pal Maynak,
Pal Mrityunjoy,
Roy Mithun
Publication year - 2020
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202003334
Subject(s) - chemistry , intersystem crossing , singlet oxygen , phenanthroline , hacat , photochemistry , fluorescence , phosphorescence , photodynamic therapy , stereochemistry , in vitro , excited state , oxygen , singlet state , organic chemistry , biochemistry , nuclear physics , physics , quantum mechanics
Four oxidovanadium (IV) complexes of 1H‐imidazo[4,5‐f][1,10]phenanthroline analogues with the general formula [VO(L) 2 ](acac) 2 ( 1 ‐ 4 ) were synthesized and characterized, and their in‐vitro photodynamic activity was evaluated. The complexes showed broad, low‐intensity d‐d bands at wavelengths from 635 nm to 775 nm in aqueous DMSO. The 1‐(pyren‐2‐yl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline oxidovanadium(IV) complex ( 4 ) exhibited remarkable photocytotoxicity in HaCaT cells, and cellular apoptosis was confirmed in an AO/EB dual‐staining assay. The IC 50 of complex 4 was 8.2 μM under visible light (400–700 nm), but it was less toxic in dark (IC 50 ∼70 μM). None of the complexes were less toxic to immortalized lung epithelial cells (IC 50 >50 μM), which suggested their activity was target‐specific. Annexin V‐FITC/PI assays performed with 2′,7′‐dichlorofluorescein diacetate indicated that apoptosis induced by the photoactivated complexes was due primarily to the intracellular generation of singlet oxygen ( 1 O 2 ), a reactive oxygen species. Photophysical studies and time‐dependent density functional theory (TD‐DFT) calculations suggested that the lowest triplet excited states of the complexes were long‐lived and facilitated effective intersystem crossing, resulting in the efficient generation of 1 O 2 with good quantum yields (0.49). The remarkable photocytotoxicity of complex 4 indicates that it is promising for the development of next‐generation oxidovanadium(IV)‐based photochemotherapeutic agents.