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In recent years, Ru(II) complexes have gained high importance in medicinal chemistry due to their significant anti-cancer activities, which are directly related to their DNA binding ability. In this report, the chemistry and cytotoxicity of two new Ru(II) complexes containing imidazole pyridine (Ru-1) and imidazole quinoline (Ru-2) have been studied. The prepared compounds were characterized using infrared (IR), nuclear magnetic resonance (NMR), mass spectrometry (MS), isothermal titration calorimetry (ITC), UV-Vis, and fluorescence spectral techniques. The structural analyses show that the Ru(II) complexes exhibit a 'piano stool' coordination geometry and they are composed of one bound arene, two sigma bonded benzil nitrogen atoms, and labile chlorine linked to Ru(II). The photo-physical properties of these complexes were examined, and they exhibit absorption peaks at 260 nm and 380 nm, which are due to the involvement of intra-ligand charge transitions (ILCT) and metal-to-ligand charge transitions (MLCT), respectively. The binding process of the Ru(II) complexes with DNA and BSA is non-covalent in nature and the binding constants of Ru-1 and Ru-2 complexes with DNA and BSA were found to be 1 × 10 5 M -1 and 1 × 10 3 M -1 , respectively. In the presence of the Ru(II) complexes, ethidium bromide (EtBr) is competitively displaced from DNA by intercalation of the Ru(II) complexes in DNA and it is well corroborated by viscosity and in silico studies. Both the ligands and Ru(II) complexes were carefully investigated in vitro for cytotoxicity against HeLa, MCF-7, and MDA-MB-231 cells. Surprisingly, both Ru(II) complexes exhibit superior cytotoxicity to cisplatin with a low LD 50 value against the examined cancer cells. Besides, an insignificant effect on HEK normal cells (LD 50 > 140 μM) was observed.

A simple and reliable colorimetric probe N , N '-bis-(4-diethylamino-2-hydroxybenzylidene)-1,10-phenanthroline-2,9-carbohydrazide (L) has been synthesised by reacting 4-(diethylamino)salicylaldehyde with 1,10-phenanthroline-2,9-dicarbohydrazide. The sensing ability of L was studied by its interactions with various f-block metal ions and other selected metal ions from s- and d-block by colorimetry, UV-visible spectrophotometry, and smartphone integrated red-green-blue (RGB) model in DMSO : H 2 O (7 : 3, v/v). The pale-yellow colour of L turns to wine-red upon interaction with uranyl ions (UO 2 2+ ) and yellow-orange in the presence of Th 4+ , Zr 4+ , Fe 3+ , and Lu 3+ ions. Other tested metal ions did not show any colour change of L. This color change offered a simple, quick, and consistent method for the selective and sensitive visual detection of trace levels of UO 2 2+ ions without any need for sophisticated instruments. Sensor L exhibits two absorption bands at 358 and 389 nm due to ligand-to-ligand charge transfer (LLCT). Upon interaction of L with UO 2 2+ and Th 4+ ions, absorption bands are exhibited at 480 nm and 422 nm, respectively, due to ligand-to-metal charge transfer (LMCT). The UV-vis spectral studies indicated the formation of a 1 : 2 ligand-to-metal complex between L and UO 2 2+ with an estimated association constant of 1.0 × 10 4 M -2 . Using L, the concentration of UO 2 2+ can be detected as low as 73 nM and 150 nM by spectrophotometry and RGB methods, respectively, without any interference from other tested ions with an RSD < 5% ( n = 3). The binding mechanism was studied by 1 H NMR titration, ESI mass, and FT-IR spectral analysis and was well supported by theoretical results. Overall, sensor L demonstrates promising analytical applicability for the detection of UO 2 2+ ions in a semi-aqueous medium.

A new dibutyl(2-oxo-2-(quinolin-8-ylamino)ethyl)phosphinate (L) was designed, synthesised and developed as a light activated optode for Th 4+ determination. The sensing performance of L was studied in solution and in the polymeric membrane phase using absorbance and emission techniques. The neutral ion carrier L exhibits weak fluorescence at 400 nm in CH 3 CN : H 2 O (9 : 1, v/v). Upon complexation of L with Th 4+ , the emission intensity at 486 nm was increased 100-fold due to chelation induced enhanced fluorescence. The L-Th 4+ binding interaction was studied using both Hill's and Job's plots. They indicate the formation of complex species in a 2 : 1 ratio with an estimated binding constant of 2.66 × 10 4 M -2 . Complex formation between L and Th 4+ was studied by NMR ( 1 H, 31 P), FTIR and LC-MS analyses. In order to synthesize a probe for the sensing of Th 4+ in 100% aqueous medium, the optode was prepared by immobilizing L as a neutral ion carrier in a PVC support using dioctyl phthalate (DOP) as a membrane solvent. The best performance of the optode was observed with a membrane composition of PVC : L : NaTPB : DOP in proportions of 35 : 5 : 3 : 57 (%, w/w) in the pH range of 4.0-8.0. The optode can detect Th 4+ concentrations down to 1.1 nM with a fast response time of 15 s and the optical response remains unaltered even after 3 months; the optode sensor can be regenerated using Na 2 EDTA solution. Finally, the optode was used for the quantification of Th 4+ in various water samples, monazite sand, and gas mantle samples.