Ru(II)‐η⁶‐benzene Complexes of Dibenzosuberenyl Appended Aroyl/Acylthiourea Ligands: In vitro Biomolecular Interaction Studies and Catalytic Transfer Hydrogenation

Abstract

A series of novel N-dibenzosuberene appended aroyl/acylthiourea ligands (L1-L4) and their Ru(II)-benzene complexes (1-4), [RuCl 2 (h 6 -benzene)L] (L = monodentate aroyl/acylthiourea ligand) was synthesized and well characterized. The coordination mode of aroyl/acylthiourea ligand with Ru ion through S (neutral monodentate) donor atom was determined by single crystal X-ray diffraction analysis. In vitro Calf thymus DNA (CT-DNA) and Bovine serum albumin (BSA) interaction of the complexes were investigated by UV-Visible, fluorescence spectroscopic and hydrodynamic methods. The results showed the intercalative mode of binding (in the order of 1 > 4 > 3 > 2) of the Ru(II)-benzene complexes with CT-DNA. The DNA (pUC19) cleavage study showed that the complexes cleaved DNA through a hydrolytic pathway. All the complexes have been thoroughly screened for their cytotoxicity against human liver carcinoma (HepG-2) and lung cancer (A549) cells under in vitro conditions. Complex 1 exhibited significant cytotoxic activity (IC 50 = 46.1 mM) towards HepG-2 cancer cell line. In addition to this, the prepared complexes have been utilized as catalyst precursors for transfer hydrogenation (TH) of ketones, aldehydes and nitro compounds using 2-propanol as a hydrogen source. The TH reactions proceeded with exceptional conversions (up to 99%) and the present catalytic system was extended to substituted aromatic/heterocyclic carbonyl and nitro compounds.

Unusual coordination mode of aroyl/acyl thiourea ligands and their π‐arene ruthenium (II) piano‐stool complexes: Synthesis, molecular geometry, theoretical studies and biological applications

“…Since, complexes having chiral thiourea ligands used for TH reactions could be synthesized from low cost materials by using a simple procedure is also potentially significant for industrial interest . In addition to this, the complexes have good in vitro cytotoxic activity against on a panel of human cancer cell lines, while maintaining low toxicity towards non‐cancer cell line . The proposed driving force of coordination through S atom was due to the presence of an intramolecular hydrogen bonding between carbonyl oxygen and thiourea N‐H forming a pseudo six‐membered ring.…”

“…From the XRD experiment, the same bond lengths found as 2.3993, 2.1218 and 2.4232; 2.3800, 2.1108 and 2.3908 Å, respectively in complexes 1 and 2 . The C=S bond length in aroyl/acylthiourea ligands were found to be in the range of 1.668–1.699 Å . Upon complexation the slight increment was observed in the C=S bond lengths due to the neutral coordination of sulfur with Ru atom.…”

“…The FTIR spectra of the ligand showed bands at 3427–3469, 3237–3241, 1654–1655 and 1222–1230 cm −1 , which matches to the υ (amidic N‐H), υ (thioamidic N‐H), υ (C=O) and υ(C=S), respectively. In all the reported aroyl/acylthiourea type ligands there was one hydrogen bond between thioamidic N − H and carbonyl oxygen (R − N − H···O=C) . The decreased thioamidic N − H stretching frequencies might be due to this hydrogen bond.…”

Biological evaluation, DNA/protein‐binding aptitude of novel dibenzosuberene appended palladium (II)‐thiourea complexes

“…[13] The Pd (II)-thiourea derivatives (1-4) were prepared by reaction of the corresponding ligands with [PdCl 2 ] in acetonitrile solvent, as shown in Scheme 1. [13] The Pd (II)-thiourea derivatives (1-4) were prepared by reaction of the corresponding ligands with [PdCl 2 ] in acetonitrile solvent, as shown in Scheme 1.…”

“…[2,9,10] This may lead to the formation of inactive trans isomers that reduce the anticancer activity. [13] Generally, the DNA-binding affinity/cytotoxicity of the compounds shows considerable attention towards several factors, including: charge, complex size, stereochemistry and hydrophobicity. In fact, the bulky ligands simplify the movement of the complex towards the target through the steric shelter and boost to enter the cell through lipophilicity.…”