Thiosemicarbazone Units Research Articles

Thiosemicarbazone Complexes of Transition Metals as Catalysts for Cross-Coupling Reactions

Catalysis of cross-coupling reactions under phosphane-free conditions represents an important ongoing challenge. Although transition metal complexes based on the thiosemicarbazone unit have been known for a very long time, their use in homogeneous catalysis has been studied only relatively recently. In particular, reports of cross-coupling catalytic reactions with such complexes have appeared only in the last 15 years. This review provides a survey of the research in this area and a discussion of the prospects for future developments.

BODIPY-Derived Polymeric Chemosensor Appended with Thiosemicarbazone Units for the Simultaneous Detection and Separation of Hg(II) Ions in Pure Aqueous Media.

Developing a simple and cheap analytical method for the selective detection and quantitative separation of toxic ions present in aqueous media is the biggest challenge faced by the chemosensing research community. Here, a 5,5-difluoro-1,3,7,9-tetramethyl-10-phenyl-5 H-dipyrrolo-diazaborinine-derived water-soluble polymer integrated with thiosemicarbazone units was rationally designed and synthesized for the simultaneous detection and separation of Hg(II) ions in pure aqueous solution. The water-soluble polymer scaffold poly( N, N'-dimethyl acrylamide- co-5,5-difluoro-1,3,7,9-tetramethyl-10-phenyl-5 H-dipyrrolo-diazaborinine-2-carbaldehyde) was synthesized by reversible addition-fragmentation chain transfer polymerization, followed by post-polymerization modification with thiosemicarbazide, leading to the formation of the target probe, P1. The nonemitting P1 exhibited bright yellow emission upon exposure to Hg(II) ions, with a limit of detection as low as 0.37 μM. This turn-on emission behavior triggered by Hg(II) ions might originate from the suppression of isomerization around the C═N bond of the thiosemicarbazone moiety caused by the formation of a coordination complex between P1 and Hg(II) ions. In addition, P1 displayed excellent selectivity toward Hg(II) ions over other metal cations. Finally, the selective removal of Hg(II) ions from an aqueous solution containing various metal ions was achieved by precipitation, which is probably caused by the fact that coordination complexes whereby Hg(II) ions acted as bridgeheads between P1 molecules had formed.

Water-Soluble Polymeric Probe for the Selective Sensing and Separation of Cu(II) Ions in Aqueous Media: pH-Tunable Detection Sensitivity and Efficient Separation by Thermal Precipitation

A thiosemicarbazone-based water-soluble polymeric probe was developed for the selective colorimetric detection of Cu(II) ions with pH-tunable sensitivity. The successful separation of Cu(II) ions from several alkali and transition metal cations by thermal precipitation was demonstrated. N,N-Dimethylacrylamide (DMA) and 3-vinylbenzaldehyde (VBA) were copolymerized by reversible addition–fragmentation chain transfer (RAFT) polymerization to produce p(DMA-co-VBA), herein P1. The aldehyde group of P1 was reacted with 4-phenylthiosemicarbazide to yield poly{DMA-co-[N-phenyl-2-(3-vinylbenzylidene)hydrazinecarbothioamide]}, [p(DMA-co-PVHC)], herein P2. Upon the addition of Cu(II) ions to an aqueous solution of P2, the color of the solution turned from colorless to yellow due to the formation of a coordination complex between the Cu(II) ions and phenylthiosemicarbazone units of P2, herein P2–Cu(II). The availability of the electron-rich imino nitrogen in the thiosemicarbazone units allowed P2 to show excellent se...

Synthesis and use of dioxime ligands for treatment of leukemia and colon cancer cells

Two new vicinal dioxime ligands containing thiosemicarbazone units (L1H2 and L2H2) were synthesized and characterized using 1H NMR, 13C NMR, heteronuclear multiple quantum correlation, mass, infrared and UV–visible spectroscopies, elemental analysis and magnetic susceptibility measurements. In addition, homotrinuclear nickel(II), copper(II) and cobalt(II) complexes with a metal‐to‐ligand ratio of 3:2 for L1H2 and L2H2 were prepared. Synthesis of nickel(II) complex containing a BF2+ bridge was carried out using a precursor hydrogen‐bridged nickel(II) complex via the template effect. All metal–ligand complexes were tested against two human cancer cell lines (HL‐60 and HT‐29) for their antiproliferative and apoptotic activities. The results showed that [Co(L2H)2(H2O)2] and [Ni(L2H)2] exhibited the strongest antiproliferative activity with IpC50 values ranging between 5 and 10 μM, while [Co(L2H)2(H2O)2] and [Ni(L2H)2] both induced necrosis of HT‐29 cells and 60 and 65% apoptosis in HL‐60 cells, respectively.

Synthesis and biological evaluation of 2-benzoylpyridine thiosemicarbazones in a dimeric system: Structure–activity relationship studies on their anti-proliferative and iron chelation efficacy

Thiosemicarbazone chelators represent an exciting class of biologically active compounds that show great potential as anti-tumor agents. Our previous studies demonstrated the potent anti-tumor activity of the 2′-benzoylpyridine thiosemicarbazone series. While extensive studies have been performed on monomeric thiosemicarbazone compounds, dimeric thiosemicarbazone chelators have received comparatively less attention. Thus, it was of interest to investigate the anti-proliferative activity and iron chelation efficacy of dimeric thiosemicarbazones. Two classes of dimeric thiosemicarbazones were designed and synthesized. The first class consisted of two benzoylpyridine-based thiosemicarbazone units connected via a hexane or dodecane alkyl bridge, while the second class of dimer consisted of two thiosemicarbazones attached to a 2,6-dibenzoylpyridine core. These dimeric ligands demonstrated greater anti-proliferative activity than the clinically used iron chelator, desferrioxamine. This study highlights the importance of optimal lipophilicity as a factor influencing the cytotoxicity and iron chelation efficacy of these chelators.

Synthesis, characterization, and in vitro anti-neoplastic activity of novel vic-dioximes bearing thiosemicarbazone side groups and their mononuclear complexes

Two novel vicinal dioxime ligands containing thiosemicarbazone units, (2E)-2-[4-(diethylamino)benzylidene]-N-[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethanimidoyl]hydrazine carbothioamide (L1H2) and (2E)-2-[4-(dimethylamino)benzylidene]-N-[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethanimidoyl]hydrazinecarbothioamide (L2H2), were synthesized. Using the HL-60 human leukemia cell line, the in vitro anti-neoplastic activity of these thiosemicarbazone-oxime derivatives was evaluated. Mononuclear nickel(II), copper(II), and cobalt(II) complexes with a metal:ligand ratio of 1:2 for both the L1H2 and L2H2 ligands were also synthesized. To characterize these compounds, Fourier transform-infrared spectroscopy (FT-IR), mass spectrometry (MS), magnetic susceptibility measurements, 1H and 13C nuclear magnetic resonance (NMR), ultraviolet–visible (UV–Vis) absorption spectroscopy, heteronuclear multiple-bond correlation (HMQC), and elemental analysis were performed. For L1H2, L2H2, and each of their derivatives, antiproliferative effects against HL-60 cells were exhibited and the associated IpC50 values ranged from 5μM to 20μM. Furthermore, L1H2 and its derivatives inhibited the proliferation of HL-60 cells more effectively than L2H2, and 5μM [Cu(L1H)2] exhibited the strongest antiproliferative activity.

Spectroscopic and biological approach of Ni(II), Cu(II) and Co(II) complexes of 4-methoxy/ethoxybenzaldehyde thiosemicarbazone glyoxime

Two novel vicinal dioxime ligands containing (4-methoxybenzaldehyde thiosemicarbazone glyoxime (L1H2) or 4-ethoxybenzaldehyde thiosemicarbazone glyoxime (L2H2)) thiosemicarbazone units were synthesized and characterized using 1H NMR, 13C NMR, HMQC, MS, infrared and, UV–VIS. spectroscopy, elemental analysis, and magnetic susceptibility measurements. Mononuclear nickel(II), copper(II) and cobalt(II) complexes with a metal:ligand ratio of 1:2 for L1H2 and L2H2 were also synthesized. The effect of pH and solvent on the absorption spectra of both ligands and complexes was determined. IR spectra show that the ligands act in a bidentate manner and coordinates N4 donor groups of the ligands to NiII, CuII and CoII ions. The detection of H-bonding (OH⋯O) in the [M(LH)2] metal complexes by IR spectra supported the square-planar MN4 coordination of mononuclear complexes. The antimicrobial activities of compounds L1H2, L2H2, and their Ni(II), Cu(II) and Co(II) complexes were evaluated using the disc diffusion method against 12 bacteria and 4 yeasts. The minimal inhibitory concentrations (MICs) against 7 bacteria and 3 yeasts were also determined. Among the test compounds attempted, L1H2, [Ni(L1H)2], [Cu(L1H)2], L2H2, [Ni(L2H)2] and [Cu(L2H)2] showed some activities against certain Gram-positive bacteria and some of the yeasts tested.

1-(4-Carb-oxy-butan-2-yl-idene)-4-phenyl-thio-semicarbazide.

The mol­ecule of the title compound, C12H15N3O2S, which belongs to the family of thio­semicarbazones, containing an acid group, adopts a semi-closed conformation with an intramolecular N—H⋯N hydrogen bond. In the crystal, molecules are linked by strong N—H⋯O and O—H⋯S hydrogen bonds between the acid group and thiosemicarbazone unit, with one additional intermolecular hydrogen C—H⋯O interaction. These three interactions form R 2 2(8) and a R 2 1(7) rings and the molecules related by the c-glide plane are linked into a zigzag chain along [001].

Benzaldehyde thiosemicarbazone

The title compound, C8H9N3S, contains two mol­ecules in the asymmetric unit. One mol­ecule is close to being planar (r.m.s. deviation from the mean plane = 0.06 Å for the non-H atoms), while the other exhibits a dihedral angle of 21.7 (1)° between the benzene ring and the mean plane of the thio­semicarbazone unit. Inter­molecular N—H⋯S hydrogen bonds link the mol­ecules into layers parallel to the (010) plane.

Spectroscopic, cyclic voltammetric and biological studies of transition metal complexes with mixed nitrogen–sulphur (NS) donor macrocyclic ligand derived from thiosemicarbazide

The complexation of new mixed thia-aza-oxa macrocycle viz., 2,12-dithio-5,9,14,18-tetraoxo-7,16-dithia-1,3,4,10,11,13-hexaazacyclooctadecane containing thiosemicarba-zone unit with a series of transition metals Co(II), Ni(II) and Cu(II) has been investigated, by different spectroscopic techniques. The structural features of the ligand have been studied by EI-mass, 1H NMR and IR spectral techniques. Elemental analyses, magnetic moment susceptibility, molar conductance, IR, electronic, and EPR spectral studies characterized the complexes. Electronic absorption and IR spectra of the complexes indicate octahedral geometry for chloro, nitrato, thiocyanato or acetato complexes. The dimeric and neutral nature of the sulphato complexes are confirmed from magnetic susceptibility and low conductance values. Electronic spectra suggests square-planar geometry for all sulphato complexes. The redox behaviour was studied by cyclic voltammetry, show metal-centered reduction processes for all complexes. The complexes of copper show both oxidation and reduction process. The redox potentials depend on the conformation of central atom in the macrocyclic complexes. Newly synthesized macrocyclic ligand and its transition metal complexes show markedly growth inhibitory activity against pathogenic bacterias and plant pathogenic fungi under study. Most of the complexes have higher activity than that of the metal free ligand.