Biological and catalytic evaluation of Ru(II)‐p‐cymene complexes of Schiff base ligands: Impact of ligand appended moiety on photo‐induced DNA and protein cleavage, cytotoxicity and C‐H activation

Abstract

Two organometallic Ru(II)‐p‐cymene complexes of the type [Ru(η6‐p‐cymene)(L)Cl]PF6 1 and 2, where L is N,N‐bis(4‐isopropylbenzylidene)ethane‐1,2‐diamine (bien, L1) or N,N‐bis (pyren‐2‐ylmethylene)ethane‐1,2‐diamine (bpen, L2) have been prepared and characterized well. Because of appended pyrenyl groups in coordinated bpen ligand, the complex 2 exhibits higher DNA and protein binding than complex 1 in which isopropylbenzyl groups are incorporated. Interestingly, the luminescent characteristic complex 2 is unique in displaying DNA cleavage after light activation by UVA light at 365 nm through oxygen dependent mechanism. AFM analysis attests the photo‐induced DNA fragmentation ability of complex 2. Also, the complex 2 cleaves the protein after light exposure in a non‐specific manner suggesting that it can act as a protein photo cleaving agent. In contrast to the trend of DNA and protein interaction of complexes, the complex 1 exhibits cytotoxic activity against human breast carcinoma (MCF‐7) and liver carcinoma (HepG2) with potency higher than that of complex 2 due to enhanced hydrophobicity of isopropyl groups present in p‐cymene and bien ligands. Indeed, complex 2 is inactive against MCF‐7 and HepG2 cancer cell lines even up to 200 μM concentration. The AO/EB staining assay reveals that the complex 1 is able to induce late apoptotic mode of cell death in breast cancer cells, which is further confirmed by inter‐nucleosomal DNA cleavage. Furthermore, the complexes 1 and 2 are evaluated for their catalytic activities and found to be working well for the β‐carboline directed C–H arylation to afford the desired products in good yield (40–47%).

Dinuclear Zn(II) and tetranuclear Co(II) complexes of a tetradentate N2O2 Schiff base ligand: Synthesis, crystal structure, characterization, DFT studies, cytotoxicity evaluation, and catalytic activity toward benzyl alcohol oxidation

“…Schiff bases are considered “exclusive ligands” because they play a key role in the development of coordination chemistry. Schiff base ligands are prepared easily and can be readily modified, both electronically and sterically . Schiff base ligands contain multiple potential donor sites, which allow them to bind metal ions with diverse coordination geometries such as bidentate and tridentate .…”

Nanoencapsulation of Ru(p-cymene) Complex Bearing Ginger-based Natural Product into Liposomal Nanoformulation to Improve Its Cellular Uptake and Antiproliferative Activity

“…In other words, to induce cytotoxicity, the Ru complexes must be taken up by the cells. Recent research has shown that ligand hydrophobicity confers increased lipophilicity, which promotes the penetration of complexes through the cell membrane, resulting in cytotoxicity. − The p -cymene ring and the appended benzyl group of the B-6GD ligand are expected to increase the permeability of Ru­(B-6GD) across the hydrophobic lipid bilayer of the cell membrane when compared to Ru ( 6G ). However, it has not been experimentally observed.…”

Synthesis, structural insights, and biological screening of DNA targeted Ru(ii)(η6-p-cymene) complexes containing bioactive amino-benzothiazole ligand scaffolds

“…Paper NJC These complexes could act as a photosensitizer when exposed to light with a wavelength in their absorption range, allowing them to attain the excited triplet state via efficient intersystem crossing from the singlet excited state. 47 The triplet state can then activate molecular oxygen, converting it from a stable triplet ( 3 O 2 ) to a reactive singlet ( 1 O 2 ) for nucleic acid degradation. In a different scenario, the excited state complex could involve direct proton or electron transfer to the surrounding base pairs, resulting in the production of reactive radicals for cleavage processes.…”