Synthesis and spectroscopic characterization of cobalt(II) thiosemicarbazone complexes

Thiosemicarbazone derivatives: Design, synthesis and in vitro antimalarial activity studies

Different types of thiosemicarbazone derivatives were designed and tested for their Drug-Like Molecular (DLM) nature by using Lipinski and Veber rules. Subsequently, compounds with DLM properties were synthesized and characterized by spectral methods. In vitro antimalarial activity studies of the synthesized thiosemicarbazone derivatives have been carried out against Plasmodium falciparum, 3D7 strain using fluorescence assay method and found that the compounds, (E)-2-(1-(4-fluorophenyl)ethylidene)hydrazine-1-carbothioamide (6), (E)-2-(1-(3-bromophenyl) ethylidene) hydrazine-1-carbothioamide (15) and (E)-2-(3,4,5-trimethoxybenzylidene) hydrazine-1-carbothioamide (29) showed notable antimalarial activity with EC₅₀ values of 13.54 μM, 15.83 μM and 14.52 μM respectively.

A new Salen-type azo-azomethine ligand and its Ni(II), Cu(II) and Zn(II) complexes: Synthesis, spectral characterization, crystal structure and photoluminescence studies

A novel Salen-type azo-azomethine ligand H2agen, 2,2'-{ethane-1,2-diylbis[nitrilomethylylidene]}bis{4-[ethylphenyldiazenyl]phenol}, formed by the 1:2M condensation of ethane-1,2-diamine with 5-[(4-ethylphenyl)diazenyl]-2-hydroxybenzaldehyde and its nickel(II), copper(II), and zinc(II) complexes were synthesized and characterized by the spectroscopic and analytical methods. The UV-vis spectra of the ligand were investigated in three organic solvents (DMSO, DMF and CHCl3). The ligand shows two absorption bands assigned to π-π(∗) and n-π(∗) transitions in the solvents used. Cu(II), and Ni(II) are tetra-coordinate binding to two phenolic oxygens and two imine nitrogens in approximate square planar geometry. Zn(II) also coordinates using the same sites like other metals but gave tetragonal configuration. Molecular structure of the Cu(II) complex [Cu(agen)] was determined by single crystal X-ray diffraction study. The X-ray data revealed that crystallographic imposed symmetry was absent for the complex molecule. In the structure, the Cu(II) ion is coordinated to two phenolate oxygen atoms and two imine nitrogen atoms of the azo-azomethine ligand with approximate square planar geometry. The ligand H2agen and its metal complexes exhibit strong blue emissions with irradiation. Fluorescence quantum yields and excited-state lifetimes for the ligand and its complexes were obtained. The H2agen ligand had a 35% quantum yield and a 3.27 ns excited-state lifetime. Complexation with metal ions caused reductions in intensities and quantum yields.

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.

Spectroscopic characterization and biological activity of dihydrazone transition metal complexes: crystal structure of 2,3-butanedione bis(isonicotinylhydrazone)

Metal complexes of the chloride, nitrate and acetate salts of Co(II), Ni(II) Cu(II), Zn(II), Cd(II) or Hg(II) with 2,3-butanedione bis(isonicotinylhydrazone) [BBINH] have been synthesized and structurally characterized. The crystal of BBINH was solved to crystallize as monoclinic system with space group of P121/c14. The formulae of the complexes were assigned based on the elemental analysis and mass spectra. The formation of BBINH complexes depend on the metal anion used. All complexes are nonelectrolytes except for the complexes 2, 3, 4 are (1:1) and 13 and 14 which are 1:2 electrolytes. BBINH behaves as a neutral tetradentate (N2O2) in the chloride complexes of Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II). In [Co2(BBINH)(H2O)Cl3]Cl⋅H2O, BBINH has the same dentate but with the two Co(II) ions. In the acetate complexes, [Ni2(BBINH-2H)(H2O)2(OAc)2]⋅3H2O and [Cu2(BBINH-2H)(OAc)2]⋅5H2O, BBINH acts as a binegative tetradentate with the two metal ions. The ligand in the nitrate complexes acts as a neutral bidentate via the two hydrazone azomethine C=NHy; the nitrate ions are ionic in the Cd(II) and Zn(II) complexes and covalent in the Ni(II) complex. The data are supported by NMR ((1)H and (13)C) spectra. The magnetic moments and electronic spectra of all complexes provide tetrahedral, square planar and/or octahedral structure. The decomposition of the complexes revealed the outer and inner solvents as well as the remaining residue based on TGA. The complexes have variable activities against some bacteria and fungi. The ligand is inactive against all tested organisms. The activity of Cd(II) and Hg(II) may be related to the geometry of the complexes.

Coordination of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with 2,5-hexanedione bis(thiosemicarbazone), HBTS: crystal structure of cis-[Pd(HBTS)]Cl2 and 1-(2,5-dimethyl-1H-pyrrol-yl)-thiourea

Metal complexes of Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pd2+ or Pt2+ with 2,5-hexanedione bis(thiosemicarbazone), HBTS; have been prepared and spectroscopically investigated. The empirical formulae of the complexes were suggested based on the elemental analysis. Single crystal of Pd(II) has been solved to be cis-form of square-planar geometry by the X-ray crystallography. 1H and 13C NMR spectra have been recorded for HBTS, Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) complexes, in DMSO-d6, showing the mode of chelation. The ligand acts as a neutral or a binegative tetradentate (N2S2) or neutral bidentate on the basis of FT-IR. The magnetic moments and electronic spectra provide information about the geometry of the complexes which supported by calculating the ligand field parameters for the Co(II) and Fe(III) complexes. The Ni(II) complex has subnormal magnetic moment (0.71 BM) indicative of a mixed stereochemistry of square-planar and tetrahedral structure. [Cu(HBTS-2H)] measured 0.93 BM indicating high interaction between the copper centers. The ligand may be ordered at the top of the spectrochemical series which giving high ligand field splitting energy (10 Dq=17,900 cm(-1) for Co2+ complex). The mass spectra of some complexes proved their stable chemical formulae while the TGA depicts the degradation steps and the final residue. In evaporating the mother liquor during the preparation of HBTS, new compound is obtained naming 1-(2,5-dimethyl-1H-pyrrol-yl)thiourea and its crystal was solved.

Synthesis and Characterization of New Palladium(II) Thiosemicarbazone Complexes and Their Cytotoxic Activity against Various Human Tumor Cell Lines

The palladium(II) bis-chelate complexes of the type [Pd(TSC(1-5))2] (6-10), with their corresponding ligands 4-phenyl-1-(acetone)-thiosemicarbazone, HTSC(1) (1), 4-phenyl-1-(2'-chloro-benzaldehyde)-thiosemicarbazone, HTSC(2) (2), 4-phenyl-1-(3'-hydroxy-benzaldehyde)-thiosemicarbazone, HTSC(3) (3), 4-phenyl-1-(2'-naphthaldehyde)-thiosemicarbazone, HTSC(4) (4), and 4-phenyl-1-(1'-nitro-2'-naphthaldehyde)-thiosemicarbazone, HTSC(5) (5), were synthesized and characterized by elemental analysis and spectroscopic techniques (IR and (1)H- and (13)C-NMR). The molecular structure of HTSC(3), HTSC(4), and [Pd(TSC(1))2] (6) have been determined by single crystal X-ray crystallography. Complex 6 shows a square planar geometry with two deprotonated ligands coordinated to Pd(II) through the azomethine nitrogen and thione sulfur atoms in a cis arrangement. The in vitro cytotoxic activity measurements indicate that the palladium(II) complexes (IC50 = 0.01-9.87 μM) exhibited higher antiproliferative activity than their free ligands (IC50 = 23.48-70.86 and >250 μM) against different types of human tumor cell lines. Among all the studied palladium(II) complexes, the [Pd(TSC(3))2] (8) complex exhibited high antitumor activity on the DU145 prostate carcinoma and K562 chronic myelogenous leukemia cells, with low values of the inhibitory concentration (0.01 and 0.02 μM, resp.).

Spectroscopic and electrochemical characterization of some Schiff base metal complexes containing benzoin moiety

The ligation behavior of bis-benzoin ethylenediamine (B2ED) and benzoin thiosemicarbazone (BTS) Schiff bases towards Ru(3+), Rh(3+), Pd(2+), Ni(2+) and Cu(2+) were determined. The bond length of M-N and spectrochemical parameters (10Dq, β, B and LFSE) of the complexes were evaluated. The redox characteristics of selected complexes were explored by cyclic voltammetry (CV) at Pt working electrode in non aqueous solvents. Au mesh (100 w/in.) optically transparent thin layer electrode (OTTLE) was also used for recording thin layer CV for selected Ru complex. Oxidation of some complexes occurs in a consecutive chemical reaction of an EC type mechanism. The characteristics of electron transfer process of the couples M(2+)/M(3+) and M(3+)/M(4+) (M=Ru(3+), Rh(3+)) and the stability of the complexes towards oxidation and/or reduction were assigned. The nature of the electroactive species and reduction mechanism of selected electrode couples were assigned.

Synthesis and characterization of 3-methyl-5-oxo-N,1-diphenyl-4,5-dihydro-1-H-pyrazole-4-carbothioamide and its metal complexes

The molecular parameters have been calculated to confirm the geometry of 3-methyl-5-oxo-N,1-diphenyl-4,5-dihydro-1-H-pyrazole-4-carbothioamide, HL. The compound is introduced as a new chelating agent for complexation with Cr(III), Fe(III), Co(II), Ni(II) and Cu(II) ions. The isolated chelates were characterized by partial elemental analyses, magnetic moments, spectra (IR, UV-vis, ESR; (1)H NMR) and thermal studies. The protonation constant of HL (5.04) and the stepwise stability constants of its Co(II), Cu(II), Cr(III) and Fe(III) complexes were calculated. The ligand coordinates as a monobasic bidentate through hydroxo and thiol groups in all complexes except Cr(III) which acts as a monobasic monodentate through the enolized carbonyl oxygen. Cr(III) and Fe(III) complexes measured normal magnetic moments; Cu(II) and Co(II) measured subnormal while Ni(II) complex is diamagnetic. The data confirm a high spin and low spin octahedral structures for the Fe(III) and Co(II) complexes. The ESR spectrum of the Cu(II) complex support the binuclear structure. The molecular parameters have also been calculated for the Cu(II) and Fe(III) complexes. The thermal decomposition stages of the complexes confirm the MS to be the residual part. Also, the thermodynamic and kinetic parameters were calculated for some decomposition steps.

Synthesis, characterization, and in vitro cytotoxic activities of benzaldehyde thiosemicarbazone derivatives and their palladium (II) and platinum (II) complexes against various human tumor cell lines

The palladium (II) bis-chelate Pd (L¹⁻³)₂ and platinum (II) tetranuclear Pt₄(L⁴)₄ complexes of benzaldehyde thiosemicarbazone derivatives have been synthesized, and characterized by elemental analysis and IR, FAB(+)-mass and NMR (¹H, ¹³C) spectroscopy. The complex Pd(L²)₂ [HL² = m-CN-benzaldehyde thiosemicarbazone] shows a square-planar geometry with two deprotonated ligands (L) coordinated to Pd^II through the nitrogen and sulphur atoms in a transarrangement, while the complex Pt₄(L⁴)₄ [HL⁴ = 4-phenyl-1-benzaldehyde thiosemicarbazone] has a tetranuclear geometry with four tridentate ligands coordinated to four Pt^II ions through the carbon (aromatic ring), nitrogen, and sulphur atoms where the ligands are deprotonated at the NH group. The in vitro antitumor activity of the ligands and their complexes was determined against different human tumor cell lines, which revealed that the palladium (II) and platinum (II) complexes are more cytotoxic than their ligands with IC₅₀ values at the range of 0.07–3.67 μM. The tetranuclear complex Pt₄(L⁴)₄, with the phenyl group in the terminal amine of the ligand, showed higher antiproliferative activity (CI₅₀ = 0.07–0.12 μM) than the other tested palladium (II) complexes.

Synthesis and spectral feature of benzophenone-substituted thiosemicarbazones and their Ni(II) and Cu(II) complexes

The ligational behavior of 2-hydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone N-substituted thiosemicarbazones towards Ni(II) and Cu(II) ions has been investigated. The isolated complexes were identified by elemental analyses, molar conductance, magnetic moment, IR, UV-vis and ESR spectral studies. The IR spectra indicated that the investigated thiosemicarbazones lost the N(2) proton or the N(2) and OH protons and act as mononegative or binegative tridentate ligands. The ligands containing methoxy group facilitate the deprotonation of OH by resonance more than the SH. Most of the Ni(II) complexes measured subnormal magnetic moments due to square-planar+tetrahedral configuration and supported by the electronic spectra. The percentage of square-planar to tetrahedral was calculated and found in agreement with the ligand splitting energy (10Dq). Also, Cu(II) complexes measured subnormal values due to the interaction between copper centers; the lower the value the higher the interaction. It was found that the substitutent has a noticeable effect on the distortion of the complex. The ESR spectra of some solid Cu(II) complexes at room temperature exhibit g(parallel)>g( perpendicular)>2.0023 confirming a square-planar structure.