The behaviour of polydentate hydrazonic ligands derived from 2-acetylpyridine towards organotin compounds. Part I: the diorganotin(IV) complexes

Organohypervalent heterocycles

This review summarizes the structural and synthetic aspects of heterocyclic molecules incorporating an atom of a hypervalent main-group element. The term "hypervalent" has been suggested for derivatives of main-group elements with more than eight valence electrons, and the concept of hypervalency is commonly used despite some criticism from theoretical chemists. The significantly higher thermal stability of hypervalent heterocycles compared to their acyclic analogs adds special features to their chemistry, particularly for bromine and iodine. Heterocyclic compounds of elements with double bonds are not categorized as hypervalent molecules owing to the zwitterionic nature of these bonds, resulting in the conventional 8-electron species. This review is focused on hypervalent heterocyclic derivatives of nonmetal main-group elements, such as boron, silicon, nitrogen, carbon, phosphorus, sulfur, selenium, bromine, chlorine, iodine(III) and iodine(V).

Biological Applications of Thiocarbohydrazones and Their Metal Complexes: A Perspective Review

Although organic compounds account for more than 99% of currently approved clinical drugs, the established clinical use of cisplatin in cancer or auranofin in rheumatoid arthritis have paved the way to several research initiatives to identify metal-based drugs for a wide range of human diseases. Nitrogen and sulfur donor ligands, characterized by different binding motifs, have been the subject in recent years of one of the main research areas in coordination chemistry. Among the nitrogen/sulfur compounds, very little is known about thiocarbohydrazones (TCH), the higher homologues of the well-known thiosemicarbazones (TSC), and their metal complexes. The extra hydrazine moiety provides the ligands of variable metal binding modes, structural diversity and promising biological implications. The interesting coordination chemistry of TCH has mainly been focused on symmetric derivatives, which are relatively simple to synthesize while few examples of asymmetric ligands have been reported. This informative review on TCHs and their metal complexes will be helpful for improving the design of metal-based pharmaceuticals for applications ranging from anticancer to antinfective therapy.

Square planar Ni(ii) complexes of acetoneN4-phenyl-thiosemicarbazone andin situgenerated benzoyl thiosemicarbazide ligands: synthesis, spectral and structural characterizations, thermal behaviour and electrochemical studies

Two novel complexes [Ni(Hapt)₂] (1) and [Ni(btsc)] (2) have been synthesized from Hapt and Hbtsc by the reaction of Ni(ii) salt.

Three Pt(ii) complexes based on thiosemicarbazone: synthesis, HSA interaction, cytotoxicity, apoptosis and cell cycle arrest

Three new Pt-based complexes with better IC₅₀values than cisplatin displayed different cytotoxicity, cycle arrest and cell uptake manners.

Main group bismuth(III), gallium(III) and diorganotin(IV) complexes derived from bis(2-acetylpyrazine)thiocarbonohydrazone: synthesis, crystal structures and biological evaluation

Up to now, the metal complexes with thiocarbonohydrazones have been comparatively rare. Herein, three main group monometallic complexes formulated as [Bi(HL)(NO3)2(H2O)] (1), [Ga(HL)2]OAc·EtOH (2) and [(Ph)2Sn(HL)(OAc)]·DMF (3), where H2L = bis(2-acetylpyrazine)thiocarbonohydrazone, have been synthesized and characterized. The crystal structures of complexes 2 and 3 have been determined by single-crystal X-ray diffraction. Growth inhibition assays have indicated that both the free ligand and the title complexes are capable of inhibiting cell proliferation growth and could slightly distinguish the human hepatocellular carcinoma HepG2 cells from normal hepatocyte QSG7701 cells. Of particular note is the fact that the bismuth(III) complex 1 is the most active compound of this study and is 14-fold more cytotoxic than H2L with an IC50 value of 2.96 ± 0.25 μM. Its possible apoptotic mechanism has been evaluated in HepG2 cells. Complex 1 promotes a dose-dependent apoptosis in HepG2 cells and the apoptosis is associated with an increase in intracellular reactive oxygen species (ROS) production and reduction of mitochondrial membrane potential (MMP).

Antimicrobial and mutagenic properties of organotin(IV) complexes with isatin and N-alkylisatin bisthiocarbonohydrazones

A new series of ligands is synthesised starting from thiocarbonohydrazide and isatin (H(2)itc) or N-alkylisatin (methyl, H(2)mtc; butyl, H(2)btc; pentyl, H(2)ptc); the X-ray structure of H(2)mtc is discussed. The bis imine ligands are reacted with diorganotin(IV) compounds, obtaining monometallic complexes. In order to establish unequivocally their coordination geometry, the X-ray structures of (C(2)H(5))(2)Sn(Hmtc)Cl.THF (THF, tetrahydrofuran) and (C(6)H(5))Sn(Hptc)Cl(2) are determined. In (C(2)H(5))(2)Sn(Hmtc)Cl.THF, the ligand results monodeprotonated and, essentially, monodentate through the sulphur atom, while in (C(6)H(5))Sn(Hptc)Cl(2) the ligand is still monodeprotonated but SNO tridentate. The organotin(IV) complexes of isatin and N-methylisatin exhibit good antibacterial activity, better than that of the corresponding N-butyl and N-pentylisatin derivatives. Gram positive bacteria are the most sensitive microorganisms. No growth inhibition of fungi is detected up to the concentration of 100 microg/ml. H(2)mtc shows mutagenic activity with and without metabolic activation, whereas no mutagenicity is found for its organotin complexes and for the other compounds.

Compositional and structural variety of diphenyllead(IV) complexes obtained by reaction of diphenyllead dichloride with thiosemicarbazones

The reactions of PbPh(2)Cl(2) in methanol with acetophenone, salicylaldehyde, pyridine-2-carbaldehyde, 2-acetylpyridine, and 2-benzoylpyridine thiosemicarbazones (HATSC, HSTSC, HPyTSC, HAcPyTSC, and HBPyTSC, respectively) were explored. Despite the similarities among these ligands, the reactions afforded solids with very diverse compositions and structural characteristics, which were in most cases analyzed by X-ray diffractometry (as was the structure of the free ligand HBPyTSC). In the complexes [PbPh(2)Cl(2)(HATSC)](2), [PbPh(2)Cl(2)(HSTSC)(2)], [(PbPh(2)Cl(HPyTSC)(2))][PbPh(2)Cl(3)(MeOH)](2), and [PbPh(2)Cl(PyTSC)] the metal atoms are surrounded by more or less distorted octahedral coordination polyhedra; if both strong and weak interactions are considered, the lead atom in [PbPh(2)Cl(AcPyTSC)] has coordination number 7 and distorted pentagonal bipyramidal coordination geometry, while [(PbPh(2)(BPyTSC))(2)(PbPh(2)Cl(4))].2MeOH contains two different types of lead atom, one with octahedral and the other with pentagonal bipyramidal coordination. The complexes (H(2)AcPyTSC)[PbPh(2)Cl(3)] and [PbPh(2)Cl(HAcPyTSC)][PbPh(2)Cl(3)], which were also isolated, could not be crystallized. All these complexes are soluble in DMSO, and the compositions of these solutions were investigated using conductivity measurements and (1)H and (207)Pb NMR spectroscopy.

Antimicrobial and mutagenic activity of some carbono- and thiocarbonohydrazone ligands and their copper(II), iron(II) and zinc(II) complexes

Several mono- and bis- carbono- and thiocarbonohydrazone ligands have been synthesised and characterised; the X-ray diffraction analysis of bis(phenyl 2-pyridyl ketone) thiocarbonohydrazone is reported. The coordinating properties of the ligands have been studied towards Cu(II), Fe(II), and Zn(II) salts. The ligands and the metal complexes were tested in vitro against Gram positive and Gram negative bacteria, yeasts and moulds. In general, the bisthiocarbonohydrazones possess the best antimicrobial properties and Gram positive bacteria are the most sensitive microorganisms. Bis(ethyl 2-pyridyl ketone) thiocarbonohydrazone, bis(butyl 2-pyridyl ketone)thiocarbonohydrazone and Cu(H2nft)Cl2 (H2nft, bis(5-nitrofuraldehyde)thiocarbonohydrazone) reveal a strong activity with minimum inhibitory concentrations of 0.7 microgram ml-1 against Bacillus subtilis and of 3 micrograms ml-1 against Staphylococcus aureus. Cu(II) complexes are more effective than Fe(II) and Zn(II) ones. All bisthiocarbono- and carbonohydrazones are devoid of mutagenic properties, with the exception of the compounds derived from 5-nitrofuraldehyde. On the contrary a weak mutagenicity, that disappears in the copper complexes, is exhibited by monosubstituted thiocarbonohydrazones.