Synthesis and structural investigation of mono- and polynuclear copper complexes of 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide

N'-(Furan-2-ylmethylene)-2-hydroxybenzohydrazide and its metal complexes: synthesis, spectroscopic investigations, DFT calculations and cytotoxicity profiling

The ligand, N'-(furan-2-ylmethylene)-2-hydroxybenzohydrazide (H2L), was synthesized characterized through various spectral studies which cleared out that the free ligand existed in keto form. The ligand upon reaction with Cu(II), Co(II), Ni(II) and Zn(II) acetates yielded complexes with stoichiometric ratio 1:2 (M:L) which has been validated through the elemental and mass spectral measurements. The IR and NMR spectral studies of the isolated complexes disclosed that the ligand chelated to metal ion in mononegative bidentate fashion via the azomethine nitrogen and deprotonated enolized carbonyl oxygen. Moreover, the DFT quantum chemical calculations designated that the ligand and Ni(II) complex exhibited the highest and lowest values of HOMO, LUMO energies and HOMO-LUMO energy gap, respectively. Furthermore, the in vitro cytotoxic activity towards HePG-2 and HCT-116 cell lines of the isolated compounds was investigated and the data cleared out that the ligand was more potent than the metal complexes.

Schiff base 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide up-regulates the antioxidant status and inhibits the progression of Ehrlich solid tumor in mice

Cisplatin is an approved cancer therapeutic drug used to treat many solid tumors but its accumulation in the kidney, which causes nephrotoxicity, limits its clinical use. Therefore, investigators seek new alternatives to cisplatin that may be more effective and/or safer. Thiosemicarbazides are of great significance due to their expected biological activity including anticancer activities. The aim of this work is the study of the antitumor effect of Schiff base 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide (HEPTS) on Ehrlich solid tumor-bearing mice in comparison to cancer therapeutic drug cisplatin. The experiment was run using sixty adult female Swiss albino mice. Mice were allocated into six groups (n = 10 mice). Healthy control, EAC control (untreated tumor), EAC + cisplatin, EAC + HEPTS, Healthy + HEPTS, and Healthy + solvent. After scarification, blood samples, liver organs, and solid tumors were collected. Tumor weights and volumes were registered. The concentrations of malondialdehyde (MDA), reduced glutathione (GSH), SOD, catalase (CAT), total antioxidant capacity (TAC), nitric oxide (NO), uric acid, creatinine, and urea were assessed. Median survival time (MST) and the percentage increase in lifespan (%ILS) were also calculated. Treatment of tumorized mice with HEPTS significantly reduced both tumor volume and weight while it significantly increased the MST, antioxidant marks and prolonged the %ILS. It also, significantly reduced MAD, creatinine, urea, uric acid, and NO levels. Compared to cisplatin, HEPTS effects were better. Our results recommend HEPTS as one of the probable cisplatin-alternatives for tumor treatment after more validation.

Spectral, Molecular Modeling, and Biological Activity Studies on New Schiff's Base of Acenaphthaquinone Transition Metal Complexes

The newly synthesized Schiff's base derivative, N-allyl-2-(2-oxoacenaphthylen-1(2H)-ylidene)hydrazine-1-carbothioamide, has been characterized by different spectral techniques. Its reaction with Co(II), Ni(II), and Zn(II) acetate led to the formation of 1 : 1 (M:L) complexes. The IR and NMR spectral data revealed keto-thione form for the free ligand. On chelation with Co(II) and Ni(II), it behaved as mononegative and neutral tridentate via O, N¹, and S donors, respectively, while it showed neutral bidentate mode via O and N¹ atoms with Zn(II). The electronic spectra indicated that all the isolated complexes have an octahedral structure. The thermal gravimetric analyses confirmed the suggested formula and the presence of coordinated water molecules. The XRD pattern of the metal complexes showed that both Co(II) and Ni(II) have amorphous nature, while Zn(II) complex has monoclinic crystallinity with an average size of 9.10 nm. DFT modeling of the ligand and complexes supported the proposed structures. The calculated HOMO-LUMO energy gap, ΔE_H-L, of the ligand complexes was 1.96–2.49 eV range where HAAT < Zn(II) < Ni(II) < Co(II). The antioxidant activity investigation showed that the ligand and Zn(II) complex have high activity than other complexes, 88.5 and 88.6%, respectively. Accordingly, the antitumor activity of isolated compounds was examined against the hepatocellular carcinoma cell line (HepG2), where both HAAT and Zn(II) complex exhibited very strong activity, IC₅₀ 6.45 ± 0.25 and 6.39 ± 0.18 μM, respectively.

Syntheses and structures of discrete copper(II) and cadmium(II) supramolecular complexes based on 1,4-diacylthiosemicarbazone ligands

Thiosemicarbazides and their metal complexes have attracted considerable interest because of their biological activities and their flexibility, which allows the ligands to bend and rotate freely to accommodate the coordination geometries of various metal centres. Discrete copper(II) and cadmium(II) complexes have been prepared by crystallization of N-[2-(2-hydroxybenzoyl)hydrazinecarbonothioyl]propanamide (H3L) with Cu(CH3COO)2 or Cd(NO3)2 in a dimethylformamide/methanol mixed-solvent system at room temperature, affording the complexes di-μ-acetato-bis{μ4-1-[(2-oxidophenyl)carbonyl]-2-(propanamidomethanethioyl)hydrazine-1,2-diido}tetracopper(II) dimethylformamide disolvate, [Cu4(C11H10N3O3S)2(C2H3O2)2]·2C3H7NO, (I), and bis{μ2-[(2-hydroxyphenyl)formamido](propanamidomethanethioyl)azanido}bis[(4,4'-bipyridine)nitratocadmium(II)] dihydrate, [Cd2(C11H12N3O3S)2(NO3)2(C10H8N2)2]·2H2O, (II). Complex (I) consists of four Cu(II) cations, two μ4-bridging trianionic ligands and two μ2-bridging acetate ligands, while complex (II) is composed of two Cd(II) cations, two μ2-bridging monoanionic ligands, two nitrate ligands and two 4,4'-bipyridine ligands. These discrete complexes are connected by hydrogen bonds and van der Waals interactions to form a three-dimensional supramolecular architecture. Compared with (I), the phenolic hydroxy group and hydrazide N atom of the thiosemicarbazide ligand of (II) are not involved in coordination and lead to a binuclear Cd(II) complex. This different coordination mode may be attributed to the larger ionic radius of the Cd(II) ion compared with the Cu(II) ion.

Synthesis, spectral, thermal and biological studies on N(-)(2,4-dinitro-phenyl)-2-mercaptoacetohydrazide and its metal complexes

Complexes of VO(2+), Cr(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Hg(2+) ions with N(-)(2,4-dinitrophenyl)-2-mercaptoacetohydrazide (H2L) have been prepared and characterized on the basis of elemental analysis, molar conductance, thermal (TGA, DTGA), spectral (IR, NMR, UV-Visible, MS) and magnetic measurements. The IR spectra show that H2L behaves in a mononegative and/or binegative bidentate manner. The sulfate bridged the two complex molecules in [Cu(HL)(H2O)2(½SO4)]⋅3H2O. The acetate functions as a monodentate in [Ni(HL)(OAc)(H2O)3] and [Cr(HL)(OAc)2(H2O)(EtOH)]. Different stereochemistries are proposed: octahedral for Cr(III), Ni(II), Hg(II) and [Cu(HL)(H2O)2(SO4)0.5]⋅3H2O, square-based pyramid for [VO(HL)2]⋅EtOH, square-planar for [Co(L)(EtOH)(H2O)]⋅H2O, [Cu(L)(H2O)2] and tetrahedral for [Zn(L)(EtOH)(H2O)], [Cd(L)(EtOH)(H2O)] and [Cu2(HL)(H2O)6]Cl3⋅H2O according to the data of electronic spectra and magnetic measurements. The TGA data support the formula and indicate the outer and inner solvents as well as the final residue. The thermodynamic parameters are calculated using the Coats-Redfern and Horowitz-Metzger methods. H2L and [Zn(L)(EtOH)(H2O)] showed the highest cytotoxic activity while H2L has a higher antioxidant activity than ascorbic acid. The ionization constant of the ligand and the stability constant of the Cu(II)H2L in absence and presence of hexamine buffer were calculated.

Copper(II) binding to flexible triethanolamine-core PAMAM dendrimers: a combined experimental/in silico approach

The structure of copper(II) complexes formed with triethanolamine (TEA) core poly(amidoamine) (PAMAM) dendrimers from generation 0 (G0) to 4 (G4) were investigated by the electron paramagnetic resonance (EPR) technique and molecular simulations. Different square planar coordination modes were detected as a function of copper(II) concentration, whose dynamic evolution relates to the high structural flexibility peculiar to this dendrimer family. Modulated by generation and solvation effects, copper(II) complexation begins at the dendrimer core and progresses to the dendrimer periphery. Differently from the ethylenediamine (EDA) core PAMAM dendrimers, the copper complexes involving the TEA core showed high mobility and saturation of the internal sites above the 1 : 1 molar ratio between the dendrimers and the ions. Therefore, by combining EPR and molecular simulations for the first time, ultimately we obtained unique information on structure, dynamics and copper interacting ability of these dendrimers which could be successfully exploited in biomedical applications.

Comparative EPR studies of Cu(ii)-conjugated phosphorous-dendrimers in the absence and presence of normal and cancer cells

EPR analysis revealed peculiar structural and dynamical properties of anticancer-activeG3B–Cu(ii) in absence and presence of normal and cancer cells.

Functionalized nanospheres for efficient sequestration of cadmium ions

This manuscript reports the synthesis, characterization and the subsequent application of thiosemicarbazide functionalized nanosilica spheres in Cd(ii) ion sequestration.

Poly[[(μ2-4,4'-bipyridyl-κ(2) N:N')bis-{μ2-N-[2-(2-hy-droxy-benzo-yl)carbamo-thio-yl]acetamidato-κ(4) O,N,O':S}bis-(nitrato-κ(2) O,O')dicadmium] di-methyl-formamide tetra-solvate]

The asymmetric unit of the title complex, {[Cd₂(C₁₀H₁₀N₃O₃S)₂(C₁₀H₈N₂)(NO₃)₂]·4C₃H₇NO}_n, consists of one Cd^II cation, one N-[2-(2-hy­droxy­benzo­yl)carbamo­thio­yl]acetamidate ligand, half a 4,4′-bipyridyl ligand, one coordinating nitrate anion and two di­methyl­formamide solvent mol­ecules of crystallization. The bipyridine ligand is completed by inversion symmetry. The metal cation exhibits a distorted penta­gonal–bipyramidal coordination geometry provided by two O and one N atoms of the thio­semicarbazide ligand, two O atoms of the nitrate anion, one S atom of a neighbouring thio­semicarbazide ligand and one 4,4′-bi­pyridine N atom. The bridging role of the thio­semicarbazide ligand through the S atom leads to centrosymmetric binuclear units, which are further linked by 4,4′-bi­pyridine units, forming polymeric chains extending along the b-axis direction. An intra­molecular N—H⋯O hydrogen bond occurs. The crystal structure also features N—H⋯O and O—H⋯O hydrogen bonds, leading to the formation of a three-dimensional network.

Copper(II) complexes with 4-carbomethoxypyrrolidone functionalized PAMAM-dendrimers: an EPR study

The internal flexibility and interacting ability of PAMAM-dendrimers having 4-carbomethoxypyrrolidone-groups as surface groups (termed Gn-Pyr), which may be useful for biomedical purposes, and ion traps were investigated by analyzing the EPR spectra of their copper(II) complexes. Increasing amounts (with respect to the Pyr groups) of copper(II) gave rise to different signals constituting the EPR spectra at room and low temperature corresponding to different coordinations of Cu(2+) inside and outside the dendrimers. At low Cu(2+) concentrations, CuN4 coordination involving the DAB core is preferential for G3- and G5-Pyr, while G4-Pyr shows a CuN3O coordination. CuN2O2 coordination into the external dendrimer layer was also contributing to G3- and G4-Pyr spectra. The structures of the proposed copper-dendrimer complexes were also shown. G4-Pyr displays unusual binding ability toward Cu(II) ions. Mainly the remarkably low toxicity shown by G4-Pyr and its peculiar binding ability leads to a potential use in biomedical fields.

Speciation of platinum in blood plasma and urine by micelle-mediated extraction and graphite furnace atomic absorption spectrometry

A highly sensitive and selective technique for the speciation of platinum by cloud point extraction prior to determination by graphite furnace atomic absorption spectrometry (GFAAS) was described. The separation of Pt(II) from Pt(IV) was performed in the presence of 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) as chelating agent and Triton X-114 as a non-ionic surfactant. The extraction of Pt(II)-HCPTS complex needs temperature higher than the cloud point temperature of Triton X-114 and pH = 7, while Pt(IV) remains in the aqueous phase. The Pt(II) in the surfactant phase was analyzed by GFAAS, and the concentration of Pt(IV) was calculated by subtraction of Pt(II) from total platinum which was directly determined by GFAAS. The effect of pH, concentration of chelating agent, surfactant, and equilibration temperature were investigated. An enrichment factor of 42 was obtained for the preconcentration of Pt(II) with 50 mL solution. Under the optimum experimental conditions, the calibration curve was linear up to 30 μgL(-1) with detection limit of 0.08 μgL(-1) and the relative standard deviation was 1.8%. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing different spiked samples (tap water, blood plasma and urine). The proposed method was applied to the speciation analysis of Pt in blood plasma and urine with satisfactory results.

Bach adsorption study for the extraction of silver ions by hydrazone compounds from aqueous solution

Sorbent materials based on a hydrazone Schiff base compound, C₁₄H₁₁BrN₄O₄, were prepared either by immobilizing the ligand into sol-gel (SG1) or bonding to silica (SG2). The sorbent materials were characterized by FT-IR, EDX, SEM, TEM, and TGA. The sorption characteristics of a matrix of eight transition metal ions (Ag⁺, Cu²⁺, Co²⁺, Ni²⁺, Fe³⁺, Pb²⁺, Zn²⁺, and Mn²⁺) using batch method were studied. Several key parameters that affected the extraction efficiency such as pH, contact time, metal ions concentration, and gel size (for SGl) were investigated and optimized. Under the optimized conditions, the physically immobilized hydrazone sorbent (SG1) exhibits highest selectivity towards Ag⁺ ions, while the chemically bonded hydrazone sorbent (SG2) exhibits high extraction for all metal ions tested. However, for practical applications such as the removal and preconcentration of Ag⁺, the physically immobilized sorbent (SG1) is preferred.

The ligational behavior of a phenolic quinolyl hydrazone towards copper(II)- ions

Background

The heterocyclic hydrazones constitute an important class of biologically active drug molecules. The hydrazones have also been used as herbicides, insecticides, nematocides, redenticides, and plant growth regulators as well as plasticizers and stabilizers for polymers. The importance of the phenolic quinolyl hydrazones arises from incorporating the quinoline ring with the phenolic compound; 2,4-dihydroxy benzaldehyde. Quinoline ring has therapeutic and biological activities whereas, phenols have antiseptic and disinfectants activities and are used in the preparation of dyes, bakelite and drugs. The present study is planned to check the effect of the counter anions on the type and geometry of the isolated copper(II)- complexes as well as the ligational behavior of the phenolic hydrazone; 4-[(2-(4,8-dimethylquinolin-2-yl)hydrazono)methyl] benzene-1,3-diol; (H₂L).

Results

A phenolic quinolyl hydrazone (H₂L) was allowed to react with various copper(II)- salts (Cl‾, Br‾, NO₃‾, ClO₄‾, AcO‾, SO₄^2-). The reactions afforded dimeric complexes (ClO₄‾, AcO‾ ), a binuclear complex (NO₃‾ ) and mononuclear complexes (the others; Cl‾, Br‾, SO₄^2-). The isolated copper(II)- complexes have octahedral, square pyramid and square planar geometries. Also, they reflect the strong coordinating ability of NO₃‾, Cl‾, Br‾, AcO‾ and SO₄^2- anions. Depending on the type of the anion, the ligand showed three different modes of bonding viz. (NN)⁰ for the mononuclear complexes (3, 4, 6), (NO)^- with O- bridging for the dimeric complexes (1, 5) and a mixed mode [(NN)⁰ + (NO)^- with O- bridging] for the binuclear nitrato- complex (2).

Conclusion

The ligational behavior of the phenolic hydrazone (H₂L) is highly affected by the type of the anion. The isolated copper(II)- complexes reflect the strong coordinating power of the SO₄^2-, AcO‾, Br‾, Cl‾ and NO₃‾ anions. Also, they reflect the structural diversity (octahedral, square pyramid and square planar) depending on the type of the counter anion.

Structural studies and anticancer activity of a novel (N6O4) macrocyclic ligand and its Cu(II) complexes

A novel (N6O4) macrocyclic ligand (L) and its Cu(II) complexes have been prepared and characterized by elemental analysis, spectral, thermal (TG/DTG), magnetic, and conductivity measurements. Quantum chemical calculations have also been carried out at B3LYP/6-31+G(d,p) to study the structure of the ligand and one of its complexes. The results show a novel macrocyclic ligand with potential amide oxygen atom, amide and amine nitrogen atoms available for coordination. Distorted square pyramidal ([Cu(L)Cl]Cl·2.5H2O (1), [Cu(L)NO3]NO(3)·3.5H2O (2), and [Cu(L)Br]Br·3H2O (4) and octahedral ([Cu(L)(OAc)2]·5H2O (3)) geometries were proposed. The EPR data of 1, 2, and 4 indicate d1x2(-y)2 ground state of Cu(II) ion with a considerable exchange interaction. The measured cytotoxicity for L and its complexes (1, 2) against three tumor cell lines showed that coordination improves the antitumor activity of the ligand; IC50 for breast cancer cells are ≈8.5, 3, and 4 μg/mL for L and complexes (1) and (2), respectively.

Poly[bis(mu-4-benzoyl-1-isonicotinoylthiosemicarbazide-kappa2N:S)dichloridocadmium(II)]

The asymmetric unit of the title complex, [CdCl(2)(C(14)H(12)N(4)O(2)S)(2)](n), consists of one Cd(II) ion located on the crystallographic inversion centre, one 4-benzoyl-1-isonicotinoylthiosemicarbazide ligand and one chloride ligand. The central Cd(II) ion adopts a distorted octahedral coordination geometry formed by two pyridyl N atoms of two ligands, two S atoms of two other ligands and two chloride ligands. The thiosemicarbazide ligands act as bridges, linking the metal ions into a two-dimensional layered structure parallel to the bc plane. Intermolecular N-H...O hydrogen bonds and C-H...pi interactions exist between adjacent layers.