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The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Fine-tuning the Photochemistry of Sulfur-Based Linkages with Ruthenium(II) Polypyridyl Complexes for Optimal PACT
Ramranjan Mishra1, Pritha Chatterjee1, Madhu Verma2
1Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
Abstract:
The thioether-based monodentate ligands are reported to be efficient photoreleasable groups from Ru(II)-photocages designed for photoactivated chemotherapy (PACT). However, the direct comparison and systematic studies of the photochemical behavior of sulfur linkages of varied electronic/oxidation states, i.e., sulfoxides, thioethers, or thiols coordinated with Ru(II)-polypyridyls, remain unexplored. To delve into the intricate photochemistry of Ru(II)-S linkages, two Ru(II)-polypyridyls: [Ru(ttpy)(phen)(DMSO)](PF6)2 [1](PF6)2 and [Ru(ttpy)(phen)(DAS)](PF6)2 [2](PF6)2, [ttpy = 4'-tolyl-2,2':6',2″-terpyridine, phen = 1,10-phenanthroline, DAS = diallyl sulfide, DMSO = dimethyl sulfoxide] were synthesized. Here, we used DMSO for the typical sulfoxide linkage, while DAS a biologically potent phytochemical, probed as a thioether linkage with Ru(II). The photosolvolysis monitored by UV/Vis and 1H NMR studies with white LED in CH3CN indicated more facile substitution of DAS than that of DMSO. The water-soluble [1](NO3)2 and [2](NO3)2 exhibited facile photorelease of DAS than DMSO from {Ru(ttpy)(phen)}2+-photocages in water. The cytotoxicity and photocytotoxicity studies with HeLa and Caco2 cells showed that [2](PF6)2 and [2](NO3)2 were more photocytotoxic with higher photoindices (PI) compared to [1](PF6)2 and [1](NO3)2. This apparently led to the conclusion that markedly facile photorelease of DAS resulted in higher photocytotoxicity of the DAS-based complexes. Therefore, thioether-based Ru(II)-polypyridyls portray better options for photocaging of prodrugs and PACT applications.
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