Thiolate Sulfur Atoms Research Articles

Structural and computational analysis of a nickel(II) complex with S-benzyldithiocarbazate Schiff base ligand: Synthesis, X-ray crystallography, MEP, HOMO-LUMO, Hirshfeld surface analysis, and molecular docking

A new compound, benzyl N-[1-(thiophen-2-yl)propylidene]hydrazinecarbodithioate (LH), and its nickel(II) complex (NiL2), were synthesized and structurally identified. Single crystal X-ray diffraction analyses determined that both the LH ligand and the NiL2 complex crystallized in the monoclinic system, with space group P21/c and Z = 4. The LH ligand exhibited lattice parameters of a = 9.661(2)Å, b = 8.995(2)Å, c = 18.939(4)Å, β = 102.677(4)°, V = 1605.7(7)Å3, whereas, NiL2 exhibited a = 17.805(7)Å, b = 10.548(4)Å, c = 18.100(7)Å, β = 108.279(6)°, V = 3228(2)Å3. The NiL2 complex was found to possess a slightly distorted square planar geometry with the LH deprotonated ligand acting as a monoanionic bidentate by coordinating through the azomethine nitrogen and thiolate sulfur atoms. It was observed that the HOMO-LUMO energy gap of the NiL2 complex (0.3654 eV) was lower than that of the LH ligand (2.4425 eV), indicating that NiL2 possesses a higher reactivity than the LH ligand. Intermolecular hydrogen bonding interactions were examined by Hirshfeld surface and 2D fingerprint analysis, which showed predominant H…H interactions for both the LH ligand and the NiL2 complex. A molecular docking simulation study with the dopamine D4 receptor (DRD4) and farnesyltransferase (FTase) revealed that NiL2 was able to interact with 13 residues in FTase, as compared to the farnesyl-Cys drug interacted with 11 residues.

Thiosemicarbazones and derived tin complexes: Synthesis, structural analysis and in vitro evaluation against bacterial and cancer cells

Two complexes of Sn (IV), Sn (IV)‐TSC 1 and Sn (IV)‐TSC 2, with the ligands 4‐(2,4‐dimethylphenyl)‐1‐([pyridin‐2‐yl]methylene)thiosemicarbazide (TSC 1) and 4‐(2,5‐dimethoxyphenyl)‐1‐([pyridin‐2‐yl]methylene)thiosemicarbazide (TSC 2) were synthesized. X‐ray crystallographic investigation of Sn (IV)‐TSC 2 afforded valuable information on its octahedral geometry, monoclinic lattice and C 1 2/c 1 space group. The ligands are monoanionic tridentate via a deprotonated thiol sulfur atom and two nitrogen atoms of pyridine and azomethine moieties. These atoms coordinate tin alongside three independent chlorine atoms making the tin atoms in the complexes tetravalent, despite of incorporating tin (II) chloride in the reactions. Solutions of the ligands TSC 1 and TSC 2 (20 mg/ml in dimethyl sulfoxide) induced growth inhibitions only to Staphylococcus aureus (14 and 10 mm) and Escherichia coli (15 and 10 mm) bacteria. But the complexes displayed activities against four bacterial species, that is, S. aureus, E. coli, Bacillus subtilis and Pseudomonas aeruginosa (complex Sn (IV)‐TSC 1, complex Sn (IV)‐TSC 2 and ampicillin showed inhibition diameters with 12–14, 13–14 and 21–26 mm). All TSC ligands and coordination compounds induced cytotoxicity in MCF‐7 cancer and BHK normal cells. The compounds TSC 1, TSC 2, Sn (IV)‐TSC 1, Sn (IV)‐TSC 2 and doxorubicin inhibited the MCF‐7 (BHK) cells with IC50 values of 68.9 (126.6), 145.4 (110.6), 22.6 (16.7), 34.2 (16.1) and 9.66 (36.42) μM, respectively.

Exploration of novel phenyl mercury tetrazole‐thione complexes: Characterization and investigating the impact of diamine ligands on enhanced hydrogen storage

AbstractTen mixed‐ligand phenyl mercury(II) complexes containing 1‐methyl‐1H‐tetrazole‐5‐thiol (HmtzS) (1) and phosphine or amine ligands. These complexes fall into two groups: [PhHg(mtzS){Ph2P(CH2)PPh2}]2 (2) and [PhHg(mtzS){Ph2P(CH2)nPPh2}] (3‐6), where n varies, and [PhHg(mtzS)(diamine)] (8‐10), with diamine choices being 2,2′‐bipyridyl (Bipy, 8), 1,10‐phenathroline (Phen, 9), or ethylenediamine (en, 10). These complexes were synthesized with moderate to high yields and characterized using various techniques. Characterization data revealed that the mtzS− ligand coordinates as a monodentate ligand through the thiolate sulfur atom in all complexes, adopting a tetrahedral geometry around the Hg(II) center. Furthermore, complexes [PhHg(mtzS)] (1) and its diamine derivatives (8‐10) were assessed for hydrogen storage at 77 K using the VTI method. Results demonstrated that the incorporation of diamines improves hydrogen storage capacity at low pressure. The precursor stored (1) 2.3 wt.% at 80 bar, while the other complexes showed storage capacities ranging from 2.9 to 3.86 wt.% at pressures of 45‐60 bar. Thermodynamic properties of the [PhHg(mtzS)(Bipy)] complex was calculated at three different temperatures. The results prove that the entropy was equal to 0.50543599 J/mol H2. K while the enthalpy equal to 0.0942638 KJ/(mol H2).

Mixed ligand Ni(II) complexes containing 2-chloroquinoline-3-carboxaldehyde-4(N)-substituted thiosemicarbazones and 2,2′-bipyridine: Synthesis, spectral characterization and in-vitro cytotoxicity

Ni(II) complexes (NiL1-NiL4) of 2-chloroquinoline-3-carboxaldehyde-4(N)-substituted thiosemicarbazones and 2,2′-bipyridine ligands were prepared and characterized by various spectroscopic techniques such as Fourier Transform Infrared (FT-IR), Ultraviolet–visible (UV–vis), 1H NMR and mass spectroscopy. The binding of the ligands to the nickel ion was through their azomethine nitrogen and thiolate sulfur atoms. The redox properties of the complexes were analyzed by cyclic voltammetry. The binding affinity of the complexes with CT-DNA (Calf Thymus DNA) and BSA (Bovine Serum Albumin) was studied using absorption and emission methods. The complex NiL3 exhibited better binding activity with high binding constant value with both DNA and BSA. Antiproliferative ability of the Ni(II) complexes (NiL1-NiL4) was explored against human cervical cancer cells HeLa and human normal embryonic kidney cells HEK. The morphological changes induced by the Ni(II) complexes on HeLa cells were analyzed by AO-EB and DAPI staining assays. The results obtained from the cytotoxicity studies showed the better cytotoxicity of the complex NiL3 towards inhibiting the growth of HeLa cells, whereas non toxic nature of the complexes was proved with HEK cells.

Spectral, band gap and DFT studies of novel cobalt (II) complexes of N(4)-cyclohexylthiosemicarbazones: Molecular docking with DNA and SARS-CoV-2 Mpro

The synthesis and characterization of four novel cobalt complexes CoL12 (1), [Co(HL2)L2]Cl (2), CoL22 (3) and [Co(HL2)L2]Br (4) of thiosemicarbazones HL1 and HL2, (where HL1 is 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone and HL2 is quinoline-2-carbaldehyde-N(4)-cyclohexylthiosemicarbazone) are reported. The new ligand HL2 was characterized physicochemically and the structure was confirmed by single crystal X-ray diffraction technique. The relevant intermolecular interactions of HL2 were quantified using Hirshfeld surface analysis. The coordination of the Schiff bases to the metal ions were assigned with the help of physicochemical methods, which indicate octahedral geometry for all the complexes. The deprotonated ligands coordinate via pyridinyl nitrogen, azomethine nitrogen and thiolate sulfur atoms in all the complexes. However, the NNS coordination of the neutral thione ligand is also present in the complexes 2 and 4. Furthermore, geometrical optimization and theoretical calculations of the compounds were achieved by density functional theory quantum chemical computational methods. The direct bandgaps of the complexes were calculated experimentally using the Kubelka-Munk model, which shows a range of 1.62–2.09 eV and corroborates with the theoretical studies. In silico molecular docking studies of all the compounds were performed with B-DNA dodecamer and are all indicative of groove mode of binding. All the compounds exhibit strong putative binding potentials toward duplex DNA. Interestingly, the putative binding efficiency of the complexes 1 and 3 with SARS-CoV-2 main protease is also found very higher compared to the repurposed drugs that are specifically active at 6Y2F.

3-acetyl-coumarin-substituted thiosemicarbazones and their ruthenium, rhodium and iridium metal complexes: An investigation of the antibacterial, antioxidant and cytotoxicity activities

A series of ruthenium, iridium and rhodium half-sandwich complexes containing 3-acetyl chromen-2-one-4(N)-substituted thiosemicarbazone derivatives have been prepared for use as antibacterial and anticancer agents. These complexes have been isolated as cationic bidentate (N, S) and neutral bidentate (N, S) complexes. The complexes have been characterized by spectral techniques (FT-IR, UV-Vis, NMR and HRMS) and single-crystal X-ray crystallography methods. The structure of complex 6 has been determined by a single-crystal X-ray diffraction study, which shows that coordination of the 3-acetyl chromen-2-one-4(N)-substituted thiosemicarbazone ligand to the metal occurs via azomethine nitrogen and thiolate sulfur atoms. Vitro antibacterial activity against gram-positive Staphylococcus aureus and gram-negative Escherichia coli, Klebsiella pneumonia strains and antioxidant activity have been evaluated. Also, the said complexes were tested for anticancer efficacy (in vitro for 48h) in Dalton's lymphoma (DL) cancer cell lines using cell cytotoxicity (MTT) and apoptosis tests. The results were compared with cisplatin (standard drug) under identical experimental conditions. The cell cytotoxicity results showed that complex 5 induced higher cytotoxicity in DL cells, followed by complex 4, 1, and 2.

Synthesis, spectroscopic and hydrogen storage studies of mono or bimercury(II) mixed ligand complexes of amines with 2-cyanoamino thiophenolate ligand

Organic heterocyclic compounds play a significant role in coordination chemistry due to their ability to act as donor atoms for coordinating with various metal or metal ions. In this study, particular attention was given to the conversion of the 2-aminobenzothiazole ligand into 2-cyanoaminothiophenolate (LH) through a ring-breaking reaction. This transformation was achieved by reacting 2-aminobenzothiazole with phenyl mercury(II) acetate in the presence of sodium hydroxide, resulting in the formation of the complex [pHHg(LH)]n. During this process, mono-deprotonation of 2-aminobenzothiazole occurred, accompanied by facial carbon-sulfur bond breaking. This complex was used as a synthon to prepare four new mononuclear and binuclear complexes, which were [pHHg(LH)(apmy)2] (apmy= 2-aminopyrimidine) and [PhHg(LH)(bipy)] and [pHHg(LH)(μ-Cl)2Hg(bipy)] and [pHHg(LH)(μ-Cl)2Hg(phen)]. The prepared complexes were characterized using melting point, elemental analysis, FTIR, 1HNMR and 13CNMR. The results showed that the 2-cyanoamino thiophenolate ligand exhibited a monodentate behavior across the thiol sulfur atom, while the nitrile group remained free. The complex [pHHg(LH)(μ-Cl)2Hg(phen)] was used to study its ability to store hydrogen at different temperatures in order to study the thermodynamic parameters (enthalpy and entropy). The study proved that the highest stored value was 1.92 wt.% H2. It was noted that this ratio can be stored at lower pressures as the temperature decreases, proving that the storage is of a physical type with the value of R2= 0.92602 for the Van't Hof plot. The enthalpy value was 0.1131118 (kJ/(mol H2) while the entropy value was 0.60649754 (J/mol H2. K).

New iron(III) complexes with 2-formylpyridine thiosemicarbazones: Synthetic aspects, structural and spectral analyses and cytotoxicity screening against MCF-7 human cancer cells

2-Formylpyridine thiosemicarbazone - iron (III) chelates [FeL2] Cl•2H2O {L = L1 (C1) [HL1 = 4-(4-Nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide] and L = L2 (C2) [HL2 = 4-(2,5-Dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide]} were prepared. The two ligand anions in each complex resulted in saturation of the iron coordination number and consequently the existence of these complexes as 1:1 electrolytes. As well, the iron in these complexes exhibits low-spin electronic configuration. X-ray crystallography of complex C1 indicated its triclinic crystal system and P 1‾ space group. In addition, it proved the ligation through a thiol sulfur atom and two nitrogen atoms of pyridine and azomethine groups. This is while the presence of two water molecules of crystallization in the complex structure was also indicated. The ligand HL1 was selected for cytotoxicity screening against human MCF-7, A-549, HEPG-2 and HCT-116 cancer cells and the most enhanced activities were detected against the breast cells. Against these cells, the compounds HL1, HL2, C1 and C2 induced cytotoxicity, respectively, with IC50 values of 52.4, 145.4, 34.3 and 62.0 μM. However, against the healthy BHK cells, HL1 and HL2 caused cytotoxicity, respectively, with IC50 values of 54.8 and 110.6 μM and cytotoxicity with percent viabilities of 56.7 and 55.4% of the BHK cells by the complexes (137.4 μM of C1 and 131.9 μM of C2) was determined. These activities against MCF-7 cells are less significant compared with the measured value for doxorubicin. But this standard is more toxic to normal cells than the thiosemicarbazones (IC50 (doxorubicin) = 9.66 μM against MCF-7 cells and 36.42 μM against BHK cells).

Magnetic coupling between Fe(NO) spin probe ligands through diamagnetic NiII, PdII and PtII tetrathiolate bridges.

Reaction of the nitrosylated-iron metallodithiolate ligand, paramagnetic (NO)Fe(N2S2), with [M(CH3CN)n][BF4]2 salts (M = NiII, PdII, and PtII; n = 4 or 6) affords di-radical tri-metallic complexes in a stairstep type arrangement ([FeMFe]2+, M = Ni, Pd, and Pt), with the central group 10 metal held in a MS4 square plane. These isostructural compounds have nearly identical ν(NO) stretching values, isomer shifts, and electrochemical properties, but vary in their magnetic properties. Despite the intramolecular Fe⋯Fe distances of ca. 6 Å, antiferromagnetic coupling is observed between {Fe(NO)}7 units as established by magnetic susceptibility, EPR, and DFT studies. The superexchange interaction through the thiolate sulfur and central metal atoms is on the order of NiII < PdII ≪ PtII with exchange coupling constants (J) of -3, -23, and -124 cm-1, consistent with increased covalency of the M-S bonds (3d < 4d < 5d). This trend is reproduced by DFT calculations with molecular orbital analysis providing insight into the origin of the enhancement in the exchange interaction. Specifically, the magnitude of the exchange interaction correlates surprisingly well with the energy difference between the HOMO and HOMO-1 orbitals of the triplet states, which is reflected in the central metal's contribution to these orbitals. These results demonstrate the ability of sulfur-dense metallodithiolate ligands to engender strong magnetic communication by virtue of their enhanced covalency and polarizability.

Trivalent Cobalt Complexes with NNS Tridentate Thiosemicarbazones: Preparation, Structural Study and Investigation of Antibacterial Activity and Cytotoxicity against Human Breast Cancer Cells

New complexes of trivalent cobalt with substituted thiosemicarbazone ligands having an NNS donor system {HL1 = 4-(4-nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide and HL2 = 4-(2,5-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} were synthesized via the in situ oxidation of divalent cobalt chloride accompanying its addition to the ligands. The complexes C1 and C2 were characterized via elemental (CHNS) analysis and 1H NMR, FT-IR and UV-Vis. spectroscopic data. Further, conductometric studies on the DMF solutions of the complexes indicated their 1:1 nature, and their diamagnetism revealed the low-spin trivalent oxidation state of the cobalt in the complexes. The X-ray diffraction analysis of complex C1 indicated that it crystallizes in the triclinic space group P-1. The metal exhibits an octahedral environment built by two anionic ligands bound via pyridine nitrogen, imine nitrogen and thiol sulfur atoms. The complex is counterbalanced by a chloride ion. In addition, two lattice water molecules were detected in the asymmetric unit of the unit cell. The ligand HL2 (20 mg/mL in DMSO) displayed inhibition zones of 10 mm against both S. aureus and E. coli, and the same concentration of the respective complex raised this activity to 15 and 12 mm against these bacterial strains, respectively. As a comparison, ampicillin inhibited these bacterial strains by 21 and 25 mm, respectively. Screening assay by HL1 on four human cancer cells revealed the most enhanced activity against the breast MCF-7 cells. The induced growth inhibitions in the MCF-7 cells by all compounds (0–100 μg/mL) have been detected. The ligands {HL1 and HL2} and complex C2 gave inhibitions with IC50 values of 52.4, 145.4 and 49.9 μM, respectively. These results are more meaningful in comparison with similar cobalt complexes, but less efficient compared with the inhibition with IC50 of 9.66 μM afforded by doxorubicin. In addition, doxorubicin, HL1 and HL2 induced cytotoxicity towards healthy BHK cells with IC50 values of 36.42, 54.8 and 110.6 μM, but surviving fractions of 66.1% and 62.7% of these cells were detected corresponding to a concentration of 100 μg/mL of the complexes (136.8 μM of C1 and 131.4 μM of C2).

Catalytic Membrane with Copper Single-Atom Catalysts for Effective Hydrogen Peroxide Activation and Pollutant Destruction.

The superior catalytic property of single-atom catalysts (SACs) renders them highly desirable in the energy and environmental fields. However, using SACs for water decontamination is hindered by their limited spatial distribution and density on engineered surfaces and low stability in complex aqueous environments. Herein, we present copper SACs (Cu1) anchored on a thiol-doped reactive membrane for water purification. We demonstrate that the fabricated Cu1 features a Cu-S2 coordination─one copper atom is bridged by two thiolate sulfur atoms, resulting in high-density Cu-SACs on the membrane (2.1 ± 0.3 Cu atoms per nm2). The Cu-SACs activate peroxide to generate hydroxyl radicals, exhibiting fast kinetics, which are 40-fold higher than those of nanoparticulate Cu catalysts. The Cu1-functionalized membrane oxidatively removes organic pollutants from feedwater in the presence of peroxide, achieving efficient water purification. We provide evidence that a dual-site cascade mechanism is responsible for in situ regeneration of Cu1. Specifically, one of the two linked sulfur atoms detaches the oxidized Cu1 while donating one electron, and an adjacent free thiol rebinds the reduced Cu(I)-S pair, retrieving the Cu-S2 coordination on the reactive membrane. This work presents a universal, facile approach for engineering robust SACs on water-treatment membranes and broadens the application of SACs to real-world environmental problems.

Crystal structure, Hirshfeld surface and computational study of 1-(9,10-dioxo-9,10-di-hydroanthracen-1-yl)-3-propano-ylthio-urea.

The title compound, C18H14N2O3S, crystallizes in the ortho-rhom-bic crystal system and Pbca space group. The thio-urea chromophore is planar to an r.m.s deviation of 0.032 Å with the thiol-ate sulfur atom being the most deviated. Bifurcated N-H⋯O intra-molecular hydrogen bonds result in an S(6) supra-molecular synthon. In the crystal, mol-ecules are linked by N-H⋯O inter-molecular hydrogen-bonding inter-actions and stabilized by C-H⋯π and π-π inter-actions. Hirshfeld surface analysis and fingerprint plot indicate the H⋯H inter-molecular contacts as the highest contributor to the overall surface contacts (38%) and this is supported by the high dispersive and electrostatic inter-action energies.

Various coordination modes of new coumarin Schiff bases toward Cobalt (III) ion: Synthesis, spectral characterization, in vitro cytotoxic activity, and investigation of apoptosis

AbstractFour Co (III) complexes containing substituted acetyl coumarin Schiff bases have been synthesized and structurally characterized using IR, UV–visible, 1H nuclear magnetic resonance (NMR), and mass spectroscopic techniques, which suggested that the complexes Co1 and Co3 have a similar type of coordination behavior with the binding of the ligands through ring carbonyl oxygen, azomethine nitrogen and enolate oxygen atoms. In complexes Co2 and Co4, the coordination was through ring carbonyl oxygen, azomethine nitrogen, and thiolate sulfur atoms and the complexes are of ML2 type. The anticancer potential of the synthesized complexes has been analyzed against cancerous cells such as human breast cancer cells (MCF‐7), human lung cancer cells (A549), and non‐cancerous Human Umbilical Vein Endothelial Cells (HUVEC). The activity of the complexes exceeded that of the ligands and the standard drug cisplatin, and the order of activity observed was Co4 &gt; Co3 &gt; Co2 &gt; Co1 &gt; cisplatin &gt; ligands. The IC50 values of the complexes were less than 5 μM in both the cancer cells and greater than 200 μM for non‐cancerous cells indicating the specificity of the complexes toward cancer cells. The morphological changes of the MCF‐7 and A549 cells with the complexes Co1‐Co4 have been studied by AO‐EB (Acridine Orange‐Ethidium Bromide) and Hoechst 33258 staining methods, and these results revealed that the complexes induce cell death only through apoptosis. Further the mode of cell death induced by the complexes has been confirmed by flow cytometric analysis. Complex Co4 showed better activity due to the electron‐donating hydroxyl group present in the seventh position of the coumarin ring. These results highlight the strong possibility of developing highly active cobalt coumarin complexes as anticancer agents.

Synthesis of tetranuclear complex of Pd(II) with thiosemicarbazone ligands derived from 2‐quinolone and its catalytic evaluation in Suzuki–Miyaura‐type coupling reactions and alkoxylation of chloroquinolines

AbstractA tetranuclear palladium(II) complex [(Pd(H‐6MOQtsc‐Ph))4] was obtained from the reaction between 6‐methyl‐2‐oxo‐1,2‐dihydroquinoline‐3‐carboxaldehyde‐4(N)‐phenylthiosemicarbazone [H2‐6MOQtsc‐Ph] and K2[PdCl4]. The ligand and the Pd(II) complex were characterized by Fourier transform infrared spectroscopy (FT‐IR), UV–visible and 1H NMR spectroscopy. X‐ray diffraction studies confirmed the tetrameric nature of the complex with the coordination of ligand through quinolone carbonyl, azomethine nitrogen and thiolate sulfur atoms, and the fourth site is occupied by 2‐quinolone nitrogen atom of the adjacent ligand. The synthesized complex was tested as catalyst in Suzuki–Miyaura coupling reaction between various chloroquinoline derivatives with phenylboronic acid. The reactions afforded unexpected C‐alkoxylated (CO coupling) products instead of more expected C‐arylated (CC coupling) products in the respective alcoholic mediums. However, the reactions with traditional aryl halides probed with very good yield of the corresponding CC coupling products.

Supramolecular Ni(II) complex aggregates with a circular linkage of intermolecular multi-hydrogen bonding frameworks based on thiosemicarbazone, and a Cu(II) complex: Synthesis, structural, DFT, electrochemical and antioxidant studies

Copper(II) and nickel(II) mixed ligand complexes were synthesized from 4-methoxysalicylaldehyde-N-phenyl-thiosemicarbazone and 3,5-lutidine. The structures of the complexes have been characterized by elemental analysis, IR, UV, 1H NMR and ESI-MS spectra, together with magnetic susceptibility measurements. Complex I was found to have a distorted square planar geometry, with coordination of azomethine nitrogen, thiolate sulfur, phenolate oxygen and pyridyl nitrogen atoms, by the single-crystal X-ray diffraction technique. Quantum chemical DFT calculations have also been carried out using the DFT/HSEH1PBE method with the cc-pVDZ basis set for C, H, N, O and S atoms, and the LANL2DZ basis set for the metal atom. The antioxidant activities of the ligand and its metal complexes were investigated by CUPRAC and DPPH assays and calculated as their trolox equivalent antioxidant capacities (TEAC). Electrochemical properties were performed with cyclic voltammetry and square wave voltammetry. Both the ligand and its metal complexes were found to have antioxidant capacity.

Synthesis, structural characterisation and antibacterial activities of lead(II) and some transition metal complexes derived from quinoline-2-carboxaldehyde 4-methyl-3-thiosemicarbazone

Some metal complexes of formulae, [PbHNNS(NO3)2], [Cu(NNS)], [Zn(NNS)2], [Ni(NNS)2] and [Cd(NNS)2] (NNS = anionic form of the Schiff base of quinoline-2-carboxaldehyde 4-methyl-3-thiosemicarbazone) have been synthesised and structurally characterised by a variety of physico-chemical techniques. The crystal structure of [PbHNNS(NO3)2] and [Zn(NNS)2] have also been determined by X-ray crystallography. The mono-ligated nitrato-complex adopts a distorted square pyramidal geometry where the thiosemicarbazone ligand coordinates to the lead(II) ion as a uninegatively charged bidentate NS chelating agent via the azomethine nitrogen atom and the thiolate sulphur atom. The third and fourth coordinations are occupied by two nitrato ligands. In the bis-ligand zinc(II) complex [Zn(NNS)2], the zinc atom adopts a distorted octahedral geometry around the zinc(II) ion, with two uninegatively charged tridentate NNS thiosemicarbazone ligands coordinating via one of the quinoline nitrogen atom, the azomethine nitrogen atom and the mercaptide sulphur atom displaying meridional coordination. Some of the metal complexes exhibit greater antibacterial activity against the Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli, as compared to the parent Schiff base ligand.

Metalloligands based on Robson-type amino-thiophenolato macrocycles for assembly of heterotrimetallic complexes.

The ability of macrocyclic Co and Ni aminothiolate complexes to act as metalloligands towards cuprate ions was established. Adduct formation is enabled by a thiolate-to-Cu+ charge transfer (CT) interaction giving stable heterotrimetallics with magnetic properties.

Synthesis, spectral characterization, DNA/BSA binding, antimicrobial and in vitro cytotoxicity of cobalt(III) complexes containing 7-hydroxy-4-oxo-4H-chromene Schiff bases

The present work deals with the synthesis and characterization of four Co(III) complexes derived from 7-hydroxy-4-oxo-4H-chromene-3-carbaldehyde-4(N)-substituted thiosemicarbazones. Structural confirmation of the complexes 2 and 3 were aided by X-ray crystallographic analysis, which revealed the coordination of azomethine nitrogen, ring carbonyl oxygen and thiol sulfur atoms of the ligands. DNA and Bovine serum albumin (BSA) binding studies brought about the binding ability of the complexes to biomolecules. The binding constant values calculated for the complexes were in the range (0.30–1.19) × 106 M−1 and the mode of interaction was found to be partially intercalative. The mechanism of quenching with BSA was static with quenching constants in the order 1012 M−1s−1. Their antimicrobial profile has been established by testing against four pathogenic bacterial and fungal species. The cytotoxic potential of the complexes were examined against MCF-7 and A549 cells by MTT assay. The IC50 values of the complexes were less than cisplatin, which indicated their greater activity over the standard drug. In addition, testing on human normal keratinocyte cells HaCaT indicated their non toxic nature. Lactate dehydrogenase (LDH) and Nitric oxide (NO) release assays supported the cytotoxic ability and suggested apoptotic mode of cell death induced by the complexes.

Synthesis, Characterization and Biological Activity of a Bidentate NS Schiff Base Containing S-Benzyl Dithiocarbazate and Its Zr(IV), Sn(II) Complexes

Zr (IV) and Sn (II) complexes were prepared with bidentate ligand, benzyl 2-(3-phenylallylidene) hydrazinecarbodithioate, derived from the condensation of S-benzyldithiocarbazate (SBDTC) with cinnamaldehyde and characterized by microanalysis, molar conductance and magnetic measurements, IR, electronic and ESI-MS studies. It was found that the ligand coordinated to the metal center through azomethine nitrogen and thiol sulfur atoms to form octahedral complexes with both the metal ions. The antimicrobial activities of the ligand and its complexes were investigated against the gram-positive and gram-negative bacteria and the fungus strain. The metal complexes showed strong activity than the free ligand.

Simultaneous cyclisation and coordination of dithizone to the fac-[Re(CO)3]+ core

The reaction of dithizone (H2dtz) with an organometallic rhenium(I) precursor; [Re(CO)5Cl] in ethanol led to the isolation of the octahedral organometallic fac-[Re(CO)3]+ core complex fac-[Re(CO)3(Hdtz)(dttz)] (1). The chelating ligand 1,2-diphenyltetrazolethione-5 zwitterion (dttz) in 1 was formed from the double deprotonation and cyclisation of dithizone in ethanol. The cyclisation of H2dtz to dttz zwitterion is a good example of the conversion of N,S-donor dithizone to S-donor ligand. Both dithizone anion Hdtz− and neutral zwitterion dttz coordinated to the fac-[Re(CO)3]+ core in which Hdtz− is coordinated as bidentate chelate via thiolate sulfur and azoic nitrogen atoms while dttz coordinated as monodentate ligand via thione sulfur atom. In addition to the synthesis, infra-red, 1H NMR, electronic properties and X-ray crystal structure of the complex 1 are reported.