Gold-Based Coronands as Hosts for M3+ Metal Ions: Ring Size Matters

The controlled, self-assembled synthesis of multinuclear coordination compounds can be performed via different approaches. Frequently, steric, geometric and/or electronic factors located at the ligand systems predefine the way in which metal ions can assemble them to large aggregates. For the compounds in the present paper, also the Pearson's acidities and preferred coordination geometries of the metal ions were used as organization principles. The ligand under study, 2,6-dipicolinoylbis(N,N-diethylthiourea), H₂L1^ethyl, possesses 'soft' sulfur and 'hard' nitrogen and oxygen donors. One-pot reactions of this compound with [AuCl(tht)] (tht = tetrahydrothiophene) and M³⁺ salts (M = Sc, Y, La, Ln, Ga, In) give products with gold-based {Au₃(L1^ethyl)₃}³⁺ or {Au₂(L1^ethyl)₂}²⁺ coronands, which host central M³⁺ ions. The formation of such units is templated by the M³⁺ ions and the individual size of the coronand rings is dependent on the ionic radii of the central ions in a way that small ions such as Ga³⁺ form a [Ga⊂{Au₂(L1^ethyl)₂}]⁺ assembly, while larger ions (starting from Sc³⁺/In³⁺) establish neutral [M⊂{Au₃(L1^ethyl)₃}] units with nine-coordinate central ions.

Colorimetric detection of fluoride ions in aqueous medium using thiourea derivatives: a transition metal ion assisted approach

This work explores the position of the hydroxyl moiety and its participation in intramolecular H-bonding towards dictating the fluoride selective colorimetric response in functionalized thiourea derivatives. The study reveals the pivotal aspect of the hydroxyl moiety in C2 towards attaining selectivity for fluoride over acetate and dihydrogenphosphate ion. Furthermore, a methodology employing stabilization of deprotonated thiourea through metal ion (Ni²⁺ and Cu²⁺) coordination is proposed for the colorimetric sensing of fluoride in water medium. The mechanism of interaction is thoroughly studied by UV-Vis, ¹H NMR, ESR spectroscopy, electrochemical techniques and further validated by DFT calculations. This study reveals the formation of an in situ Ni²⁺ complex that shows greater stability in aqueous medium. The methodology is applied in the detection of fluoride in groundwater samples.

Synthesis, X-ray, Hirshfeld surface analysis, exploration of DNA binding, urease enzyme inhibition and anticancer activities of novel adamantane-naphthyl thiourea conjugate

1-(adamantane-1-carbonyl-3-(1-naphthyl)) thiourea (C₂₂H₂₄N₂OS (4), was synthesized by the reaction of freshly prepared adamantane-1-carbonyl chloride from corresponding acid (3) with ammonium thiocyanate in 1:1 M ratio in dry acetone to afford the adamantane-1-carbonyl isothiocyanate (2) in situ followed by treatment with 1-naphthyl amine (3). The structure was established by elemental analyses, FTIR, ¹H, ¹³C NMR and mass spectroscopy. The molecular and crystal structure were determined by single crystal X-ray analysis. It belongs to triclinic system P - 1 space group with a = 6.7832(5) Å, b = 11.1810(8) Å, c = 13.6660(10) Å, α = 105.941(6)°, β = 103.730(6)°, γ = 104.562(6)°, Z = 2, V = 910.82(11) ų. The naphthyl group is almost planar. In the crystal structure, intermolecular CH···O hydrogen bonds link the molecules into centrosymmetric dimers, enclosing R₂²(14) ring motifs, while the intramolecular NH···O hydrogen bonds enclose S(6) ring motifs, in which they may be effective in the stabilization of the structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H … H (59.3%), H … C/C … H (19.8%) and H … S/S … H (10.1%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packing. DFT, molecular docking and urease inhibition studies revealed stability and electron withdrawing nature of 4 as compared to DNA base pairs and residues of urease. The DNA binding results from docking, UV- visible spectroscopy, and viscosity studies indicated significant binding of 4 with the DNA via intercalation and groove binding. Further investigation of the compound was done on hepatocellular carcinoma; Huh-7 cell line as well as normal human embryonic kidney; Hek-293 cell line. The compound showed significant cytotoxic activity against Huh-7 cells in comparison to normal Hek-293 cells indicating selective cytotoxicity towards cancer cells.

Synthesis, characterization, theoretical, molecular docking and in vitro biological activity studies of Ru(II) (η6-p-cymene) complexes with novel aniline substituted aroyl selenoureas

A sequence of aroyl selenourea ligands (L1-L3) substituted by aniline and their Ru(II) (η⁶-p-cymene) complexes (1-3), [Ru(II) (η⁶-p-cymene) L] (L = monodentate aroyl selenourea ligand) have been synthesized and characterized the composition of the ligands and their metal complexes. The molecular structures of ligand L1 and complex 3 were also confirmed by single XRD crystal method. The single-crystal XRD study showed that aroyl selenourea ligand coordinates with Ru via Se novel neutral monodentate atom. In vitro DNA interaction studies were investigated by Fluorescence and UV-Visible spectroscopic methods which showed that the intercalative mode of binding is in the order of 1 > 2 > 3 with Ru(II) (η⁶-p-cymene) complexes. Spectroscopic methods have been used for measuring the binding affinity of bovine serum albumin to complex. Moreover, the cytotoxic study of complexes (1-3) were evaluated against HeLa S3, A549, and IMR90 cells, resulting in complexes 1 and 2 showed promising cytotoxic activity against HeLa S3 cell with IC₅₀ values of 24 and 26 µM, respectively. Also, the morphological changes of HeLa S3 and A549 cells were confirmed by fluorescence microscope in the presence of complexes 1 and 2 using AO (acridine orange, 200 µM) and EB (ethidium bromide, 100 µM). In addition, the docking results strongly support the protein binding studies of the complexes.Communicated by Ramaswamy H. Sarma.

Fluorescence studies and photocatalytic application for hydrogen production of ZnII and CdII complexes with isophthaloylbis(thioureas)

TiO₂-based semiconductor composites containing Zn^II and Cd^II complexes produced more hydrogen gas than pure TiO₂.

Indium(iii) {2}-metallacryptates assembled from 2,6-dipicolinoyl-bis(N,N-diethylthiourea)

{2}-Metallacryptates are constructed from the self-assembly of 2,6-dipicolinoylbis(N,N-diethylthiourea) ligands and mixtures of indium(iii) chloride and chlorides of monovalent cations.

Half-sandwich Ru(η6-p-cymene) complexes featuring pyrazole appended ligands: Synthesis, DNA binding and in vitro cytotoxicity

Organometallic Ru(II)-arene complexes have emerged as potential alternatives to platinum appended agents due to their wide range of interesting features such as stability in solution and solid, significant activity, less toxicity and hydrophobic property of arene moiety, etc. Hence, a series of Ru(II)-p-cymene complexes, [(η⁶-p-cymene)Ru(η²-N,N-L1)Cl]Cl (1), [(η⁶-p-cymene)Ru(η¹-N-L2)Cl₂] (2) and [(η⁶-p-cymene)Ru(η¹-N-L3)Cl₂] (3) were prepared from pyrazole based ligands [2-(1H-pyrazol-3-yl)pyridine (L1), 3-(furan-2-yl)-1H-pyrazole (L2) and 3-(thiophen-2-yl)-1H-pyrazole (L3)], and [RuCl₂-(η⁶-p-cymene)] dimer. The new Ru(II)-p-cymene complexes were well characterized by elemental analysis, and spectroscopic (FT-IR, UV-Visible, ¹H NMR, ¹³C NMR and mass) and crystallographic methods. The Ru(II)-p-cymene complexes (1-3) were found to adopt their characteristic piano stool geometry around Ru(II) ion. The calf thymus DNA (CT-DNA) binding ability of the new complexes was investigated by electronic absorption spectroscopic titration and viscosity methods. The molecular docking study results showed that complex 1 strongly bound with targeted biomolecules than 2 and 3. Docked poses of bidentate pyrazole based Ru(II)-p-cymene complex 1 revealed that the complex formed a crucial guanine N⁷ position hydrogen bond with DNA receptor. Complexes 1-3 might hydrolyze under physiological conditions and form aqua complexes 4-8, and docking calculations showed that the aqua complexes bound strongly with the receptors than original complexes. The in vitro cytotoxicity of the Ru(II)-p-cymene complexes and cisplatin was evaluated against triple negative breast cancer (TNBC) MDA-MB-231 cells. Our results showed that the inhibitory effect of bidentate pyrazole based Ru(II)-p-cymene complex 1 on the growth of breast cancer cells was superior to other tested complexes.

Highly active copper(i) complexes of aroylthiourea ligands against cancer cells – synthetic and biological studies

Copper(i) complexes containing sulfur donor monodentate aroylthiourea ligands have been synthesized and evaluated for their biological applications.

Synthesis, structural and antimicrobial studies of type II topoisomerase-targeted copper(II) complexes of 1,3-disubstituted thiourea ligands

A series of Cu(II) complexes of 3-(trifluoromethyl)phenylthiourea derivatives was synthesized. Their structural properties were investigated by spectroscopic techniques (infrared and electron paramagnetic resonance), as well as molecular modeling. All studied coordination compounds are mononuclear complexes containing two chelating ligands bonded to the metal cation via S and deprotonated N atoms. The new chelates were evaluated for their antimicrobial potency. The complex of 1-(3,4-dichlorophenyl)-3-[3-(trifluoromethyl)phenyl]thiourea (3) presented the highest activity against Gram-positive pathogens, even stronger than the activity of its non-complexed counterpart and the reference drug. The compound also prevented the biofilm formation of methicillin-resistant and standard strains of staphylococcal cocci. The title derivatives were found to be effective inhibitors of DNA gyrase and topoisomerase IV isolated from Staphylococcus aureus. The binding modes of the ligand L3 with DNA gyrase and topoisomerase IV were presented.

Cell cytotoxicity and serum albumin binding capacity of the morin-Cu(ii) complex and its effect on deoxyribonucleic acid

The dietary components, flavonoids, are important for their anti-oxidant properties and the ability to act as metal ion chelators. The characterization of the morin-Cu(ii) complex is executed using elemental analysis, FTIR and mass spectroscopy. DNA cleaving and cell cytotoxicity properties followed by serum albumin binding have been investigated in this report. The morin-Cu(ii) complex was found to cleave plasmid pBR322 DNA via an oxidative pathway as revealed by agarose gel based assay performed in the presence of some scavengers and reactive oxygen species. The breaking of the deoxyribose ring of calf thymus DNA (ct-DNA) was also confirmed by the formation of thiobarbituric acid reacting species (TBARS) between thiobarbituric acid and malonaldehyde. The morin-Cu(ii) complex is able to inhibit the growth of human HeLa cells. Fluorescence studies revealed that the morin-Cu(ii) complex can quench the intrinsic fluorescence of serum albumins (SAs) via a static quenching method. The binding constants were found to be in the order of 10(5) M(-1) and observed to increase with temperature. Both ΔH° and ΔS° are positive for the binding of the morin-Cu(ii) complex with serum albumins which indicated the presence of hydrophobic forces. Site-selectivity studies reveal that the morin-Cu(ii) complex binds to both site 1 (subdomain IIA) and site 2 (subdomain IIIA) of human serum albumin (HSA) and bovine serum albumin (BSA). Circular dichroism (CD) studies showed the structural perturbation of SAs during binding with the morin-Cu(ii) complex. The results from binding studies confirmed that after complexation with the Cu(ii) ion, morin alters its mode of interaction with SAs which could have differential implications on its other biological and pharmaceutical properties.

Synthesis of Ru(ii)–benzene complexes containing aroylthiourea ligands, and their binding with biomolecules and in vitro cytotoxicity through apoptosis

Ru(ii)(η⁶-benzene) complexes containing sulfur donor monodentate aroylthiourea ligands have been synthesized and evaluated for their biological applications.

Synthesis and structural characterization of electrochemically reversible bisferrocenes containing bis(acyl-thiourea)s: enantiomers and conformers

Enantiomeric and conformational isomers of chiral bisferrocenyl-modified bis(acyl-thiourea)s; their crystal packing and electrochemically reversible redox reaction properties.

Structural diversity in aroylthiourea copper complexes – formation and biological evaluation of [Cu(i)(μ-S)SCl]2, cis-Cu(ii)S2O2, trans-Cu(ii)S2O2 and Cu(i)S3 cores

Four different copper complexes containing aroylthiourea ligands displayed good interaction with CT DNA and BSA and cytotoxicity.

Half-sandwich RuCl2(η6-p-cymene) core complexes containing sulfur donor aroylthiourea ligands: DNA and protein binding, DNA cleavage and cytotoxic studies

Ru(ii)(η⁶-p-cymene) complexes containing sulfur donor monodentate aroylthiourea ligands have been synthesized for exploring their biological applications.

Ru(ii)-p-cymene complexes containing esters of chiral d/l-phenylalanine derived aroylthiourea ligands for enantioselective reduction of pro-chiral ketones

The chiral Ru(ii)-p-cymene complexes are efficient catalysts for the enantioselective reduction of ketones to chiral alcohols.

Half-sandwich Ru(η6-C6H6) complexes with chiral aroylthioureas for enhanced asymmetric transfer hydrogenation of ketones – experimental and theoretical studies

The efficiency of Ru–benzene complexes towards ATH of ketones was studied.

Copper(ii) complexes of salicylaldehydes and 2-hydroxyphenones: synthesis, structure, thermal decomposition study and interaction with calf-thymus DNA and albumins

The characterized copper(ii) complexes with substituted salicylaldehydes and 2-hydroxyphenones exhibit enhanced affinity for DNA and albumins in comparison to free ligands.