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Reactions of FeSO4 precursor with thiosemicarbazones Hatc-R, where R is ethyl (Et) or phenyl (Ph), led to the formation of homoleptic iron(III) complexes of the type [Fe(atc-R)2]HSO4. The characterization of the compounds was performed by spectroscopy techniques, such as FTIR, UV–Vis, besides elemental analysis, conductometry, voltammetry and magnetic susceptibility measurement. The crystalline structure of [Fe(atc-Ph)2]HSO4·H2O was determined by single-crystal X-ray diffraction and revealed the oxidation of the Fe(II) centre to Fe(III) upon complexation of the monoanionic N,N,S-tridentate thiosemicarbazonate ligands. The magnetic susceptibility results showed the paramagnetic property of the iron(III) complexes in the extension of 1 unpaired electron. The electrochemical analyses showed a nearly reversible process of the iron complex, which is slightly influenced by the peripheral substituent groups at the N(4) position of the atc-R1− ligands. Hirshfeld surface analysis revealed that the supramolecular structure of [Fe(atc-Ph)2]HSO4·H2O is stabilized mainly by H···H, C···H/H···C and O···H/H···O interactions.

The present study reports the synthesis and crystal structures of Cu(II) complexes with pyridoxal S-allyldithiocarbazate (H2L1) and pyridoxal thiosemicarbazones (H2L2 = pyridoxal-N4-phenyl-3-thiosemicarbazone and H2L3 = pyridoxal-N4-semicarbazone). The single-crystal X-ray study reveals that in all cases, the Schiff base coordinated tridentately through the ONS-donor atoms, resulting in distorted square planar coordination geometries with the copper atoms. The Cu(II) complexes with pyridoxal dithiocarbazate, [Cu(HL1)Cl]·H2O and [Cu(HL1)Br]·H2O, as well as three complexes with pyridoxal thiosemicarbazone, [Cu(HL2)Cl]·dmf, [Cu(HL2)Br]·H2O·dmf and [Cu(H2L3)Br]Br·H2O, were also characterized by spectroscopic and physical–chemical analyses. The cytotoxicity of the complexes toward two kinds of cancerous cells (Ehrlich and S-180 cells) was evaluated by an MTT assay. The complex [Cu(H2L3)Br]Br·H2O was selected to study both the cellular and molecular mechanisms underlying its promising cytotoxicity. The Hoechst 33342/PI dual-staining assay showed the typical apoptotic morphology of cancer cells, and the RT-qPCR analysis revealed that the expressions of Bax, Casp3, Casp8, Casp9 and TP53 were markedly increased in both the Ehrlich and S-180 cells exposed to 10 μM for 3 h. According to our results, this complex induces cell death through apoptosis, showing potential as a future drug against cancer. Five stable copper(II) complexes with pyridoxal have been synthesized and their crystal structure has been studied. Spectroscopy experiments and cytotoxic assays against S-180 and Ehrlich cancer cell lines were performed and showed promising results as novel antitumor drugs.

Four chalcone–thiosemicarbazones (C-TSCs) of the type 2-((E)-3-(4-R-phenyl)-1-phenylallylidene)-N-phenylhydrazinecarbothioamide, where R = Cl (HL1), NO2 (HL2), CH3 (HL3) or CN (HL4), were prepared in good yields from the reaction of the respective chalcone with 4-phenyl-3-thiosemicarbazide and HCl in EtOH. Reaction of HL with CuCl2·2H2O or ZnCl2 in the presence of Et3N afforded the complexes [M(L)2], M = Cu(II) or Zn(II). X-ray diffraction analysis revealed that the ligands coordinate in their deprotonated form, in a bidentate fashion through the iminic nitrogen and sulfur atoms. Yeast activities of the compounds were tested, where the ligand HL4 was the most damaging derivative, exhibiting cell viability at about 50%. On the other hand, lipid peroxidation assays revealed that the ligand HL1 was able to better induce membrane damage compared to the other compounds. It has been found that coordination with Cu(II) and Zn(II) did not increase the biological activities of the C-TSCs.

A Cu(II) complex of 2-hydroxyacetophenone N(4)-phenyl semicarbazone (H2L) has been prepared, and its crystal structure is reported. The single-crystal X-ray study reveals a dimeric structure with a distorted square planar coordination geometry around each copper atom, with an ONO-donor ligand and µ2-oxo group located between the two copper atoms. The secondary coordination sphere of Cu(II) is six-coordinate, with a NO3 − ion and methanol solvent molecule making weak interactions. Supramolecular interactions involving the adjacent complexes were investigated. The complex [Cu(HL)]2(CH3OH)2(NO3)2 was also characterized by physicochemical and spectroscopic methods. The biological activity of the free semicarbazone and its Cu(II) complex were evaluated by cytotoxicity assays against human cancer cell lines. A dimeric stable complex between copper(II) and semicarbazone ligand has been synthesized, and the crystal structure has been studied. Spectroscopy experiments and cytotoxicity assays against human cancer cell lines were performed.

A Schiff base derived from naringenin (NTSC) and its complex with Cu(II) ([Cu(H3L)(OAc)]·H2O, Cu(II)–NTSC) have been synthesized and characterized by physicochemical and spectroscopic methods. EPR studies confirmed that nitrogen, oxygen, and sulfur are the donor atoms bound to Cu(II) in the complex. The geometry of the complex has been modelled using DFT methods. Furthermore, naringenin and NTSC were used for the formation of Cu(II) complexes in solution, for comparison of biological activities. Antioxidant studies confirmed better radical scavenging activity of both NTSC and its Cu(II) complex compared to naringenin. The interaction of these compounds with calf thymus DNA was monitored by UV–Vis spectroscopy.

Two new bis(thiosemicarbazone) ligands having a halogen substituent on the non-coordinating phenyl rings, namely 2-[1-(2-{3-[2-({2-[(4-bromoanilino)carbothioyl]hydrazono} methyl)phenoxy]propoxy}phenyl)methylidene]-N1-(4-bromophenyl)-1-hydrazinecarbothiamide (H 2 L3) and 2-[1-(2-{3-[2-({2-[(4-bromoanilino)carbothioyl]hydrazono}methyl)phenoxy]-2-hydroxypropoxy}phenyl) methylidene]-N1-(4-bromophenyl)-1-hydrazinecarbothiamide (H 3 L4), were used in the synthesis of a series of CuII and NiII complexes [Cu(L3)]·MeOH, [Cu(HL4)], [Ni(L3)], and [Ni(HL4)]·MeOH. The complexes were characterized by physicochemical and spectroscopic methods. Single-crystal X-ray structures of [Cu(L3)]·MeOH, [Cu(HL4)], and [Ni(L3)] showed that the metal centers are coordinated by two imine nitrogen atoms and two sulfur atoms in a distorted square-planar coordination geometry. Electrochemical investigations showed that all of these CuII and NiII complexes were reversibly reducible. Although the bromine substituent on the phenyl ring and the hydroxyl group are far from the metal centers, they have an effect on the redox potentials of the NiII/I and CuII/I couples.

Two unsymmetrical oxovanadium complexes [VO(satsc)(dpq)] (1) (satsc = salicylaldehyde thiosemicarbazone, dpq = pyrazino[2,3-f][1,10]phenanthroline) and [VO(hntdtsc)(dpq)] (2) (hntdtsc = 2-hydroxy-1-naphthaldehyde thiosemicarbazone) have been synthesized and characterized. Both complexes show strong interactions with calf thymus DNA through an intercalative model and can efficiently cleave pBR322 DNA after irradiation with light. Both complexes also exhibit high cytotoxicities against SH-SY5Y, MCF-7 and SK-N-SH cell lines. Complex 2 was found to have higher antitumor potency, DNA-binding affinity and DNA-cleaving ability than complex 1. The abilities of these complexes to scavenge hydroxy radicals were evaluated.

Three nickel(II) thiosemicarbazone complexes have been synthesized and characterized by spectroscopic and physicochemical techniques. The molecular structures of two of the complexes have been determined by single-crystal X-ray diffraction studies. In both of these complexes, the nickel center is coordinated by two tridentate ligands in a meridional fashion using C=S, C=N and neutral hydroxyl OH donors. The ligand is bound to nickel in its thione form in all three complexes. The synthesized compounds were tested for antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi. Additionally, all the compounds were screened for antituberculosis activity. Several complex/organism combinations returned an MIC value of 0.8 μg/mL or better, which is almost 8 times more active than the standard (streptomycin, 6.25 μg/mL).

Nickel(II) complexes with 2,3-dihydroxybenzaldehyde N4-substituted thiosemicarbazone ligands (H3L1–H3L4) have been synthesized and characterized with the aim of evaluating the effect of N4 substitution in the thiosemicarbazone moiety on their coordination behavior and biological activities. Two series of nickel(II) complexes with the general formulae [Ni(H3L)(H2L)]ClO4 and [Ni2(HL)2] were characterized by analytical and spectral techniques. The molecular structure of one of the complexes, namely, [Ni(H3L4)(H2L4)]ClO4 was established by single crystal X-ray diffraction studies. The crystal structure of this complex revealed that two H3L4 ligands are coordinated to nickel(II) in different modes; one as a neutral tridentate ONS ligand and the other is as a monoanionic tridentate (ONS−) ligand. The antimicrobial activities of the compounds were tested against 25 bacterial strains via the disc diffusion method, and their minimum inhibitory concentration (MIC) and minimum microbicidal concentration were evaluated using microdilution methods. With a few exceptions, most of the compounds exhibited low-to-moderate inhibitory activities against the tested bacterial strains. However, the complexes [Ni2(HL3)2] (7) and [Ni2(HL4)2] (8) indicated higher inhibitory activity against Salmonella enterica ATCC 9068 (MIC values 15.7 and 50 μg/ml). The toxicities of the compounds were tested on brine shrimp (Artemia salina), where no meaningful toxicity level was noted for both the free ligands and the complexes. The cytotoxicities of the compounds on cell viability were determined on MCF7, PC3, A375, and H413 cancer cells in terms of IC50; complexes [Ni(H3L3)(H2L3)]ClO4 (3), [Ni2(HL3)2] (7) and [Ni2(HL4)2] (8) exhibited significant cytotoxicity on the tested cell lines.

A planar, polycyclic and aromatic hydrocarbon ligand, namely 9,10-phenanthrenequinone semicarbazone, and its transition metal complexes have been synthesized and structurally characterized. The in vitro antiproliferative activity of these compounds against five human cancer cell lines revealed that they were effective against androgen receptor-positive/negative prostate cancer cells as well as COX-positive pancreatic BxPC-3 cancer cell line. The driving force behind such antiproliferative activity seems to be the up-regulated COX expression in these cells, which was amenable for targeting through metal complexation. These structural motifs can, therefore, serve as a starting point for developing novel cytotoxic agents against the growing number of prostate and pancreatic cancers.

Four Co(II) complexes, [Co(HL)2](OAc)2, [Co(HL)2Cl2], [Co(HL)2(MeOH)2](NO3)2, and [Co2(HL)4(SO4)2] (HL = acetone-N(4)-phenylsemicarbazone) were synthesized and characterized by physicochemical and spectroscopic methods. The magnetic susceptibility measurements indicate that the complexes are paramagnetic with three unpaired electrons. In all the complexes, the semicarbazone is coordinated as a neutral bidentate ligand. The structure of [Co(HL)2(MeOH)2](NO3)2 was confirmed by single crystal X-ray crystallography. The ligand is neutral and bidentate, being coordinated to the cobalt atom through the carbonyl oxygen and the azomethine nitrogen. Intermolecular hydrogen bonding and C–H···π interactions combine to stabilize the crystal structure. The ligand and its two complexes [Co(HL)2Cl2] and [Co(HL)2(MeOH)2](NO3)2 were screened for their antibacterial and antifungal activities using disk diffusion methods.

Six Cu(II) complexes of Schiff base ligands of arylidene-2-(4-(4-bromo/methoxy-phenyl)thiazol-2-yl) hydrazines have been synthesized, characterized and screened for DNA cleavage and antimicrobial activities. The chemical structures of the complexes were deduced by physicochemical and spectroscopic methods. Elemental analyses indicated that the stoichiometry of the complexes is CuL2 (L = Schiff base ligand). The DNA cleavage activities of the complexes were evaluated by agarose gel electrophoresis in the presence and absence of oxidant (H2O2) and free radical scavenger (DMSO). All the six complexes showed significant nuclease activity in the presence of H2O2, and two of the complexes showed moderate nuclease activity even in the absence of oxidant. The complexes did not show nuclease activity in the presence of free radical scavenger. The compounds were tested for activity against selected bacteria and fungi.

A tridentate nitrogen-sulfur Schiff base, 3-methylbenzyl 2-(6-methylpyridin-2-ylmethylene)hydrazine carbodithioate (6mpyS3M), was synthesized by condensation of 6-methylpyridine-2-aldehyde with S-3-methylbenzyldithiocarbazate. It crystallized in space group P 21/n. It displayed intermolecular N–H···N hydrogen bonding between the α-nitrogen and the pyridyl nitrogen. The thione sulfur is in a trans position with respect to the 6-methylpyridine fragment across the C–N bond but adopts a cis position with the 3-methylbenzyl fragment through the C–S bond. Octahedral complexes containing two 6mpyS3M ligands were prepared with Cu(II), Ni(II), Zn(II) and Cd(II). 6mpyS3M and its metal complexes were assayed against selected microbes and two breast cancer cell lines. 6mpyS3M was strongly active against both cancer cell lines. Its metal complexes showed high selectivity with Cu(II), Ni(II) and Zn(II) complexes strongly active against only one of the cancer cell lines, whereas the Cd(II) complex was strongly active only against the other. Only Cu(II) and Cd(II) complexes were active against some of the bacteria.

An oxovanadium complex [VO(satsc)(bipy)] (1) (satsc = salicylaldehyde thiosemicarbazone, bipy = 2,2′-bipyridine) and its dibromo derivative [VO(3,5-dibrsatsc)(bipy)] (2) (3,5-dibrsatsc = 3,5-dibromosalicylaldehyde thiosemicarbazone) have been synthesized and characterized by elemental analysis, IR, ES-MS and 1H NMR. The interaction of these two complexes with calf-thymus DNA (CT-DNA) was studied using UV/Vis, fluorescence spectroscopic titration, viscosity measurements and thermal denaturation. The results suggest that complexes 1 and 2 interact with CT-DNA by intercalative modes. The DNA-binding affinity of complex 1 is larger than that of complex 2. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated by gel electrophoresis experiments. Both complexes exhibit significant DNA cleavage activity, and complex 1 showed greater cleaving efficiency than complex 2.

A new series of mixed ligand semicarbazone or thiosemicarbazone complexes of Ru(II) having the general formula [RuCO(EPh3)(B)L] (where E = P or As; B = PPh3, AsPh3 or Pyridine; L = dibasic tridentate ligand derived by the condensation of ethylacetoacetate/methylacetoacetate and thiosemicarbazide/semicarbazide) have been synthesized and characterized by physico-chemical, spectroscopic and electrochemical studies. A comparative study on the catalysis of oxidation of benzyl alcohol, cyclohexanol, cinnamyl alcohol, n-butanol, n-propanol and iso-butyl alcohol has been done with N-methylmorpholine-N-oxide and molecular oxygen as co-oxidants. Catalytic activity studies of the complexes in coupling reactions have been carried out. The antibacterial properties of the complexes have also been examined.

Ozdemir, Namik/0000-0003-3371-9874; Guveli, Sukriye/0000-0001-7384-822X; Ulkuseven, Bahri/0000-0001-6342-1505 WOS: 000265835400003 Reactions of 5-bromo-2-hydroxy-benzaldehyde-S-R-4-R-1-thiosemicarbazones, [R, R-1 = H,H (L-1); CH3, H (L-2); H, C6H5 (L-3); CH3, C6H5 (L-4)] with [Ni(PPh3)(2)Cl-2] in 1:1 molar ratio yielded complexes of general formula [Ni(L)(PPh3)]. While the complexes of L-1 and L-3 involve the ONS donor set of the thiosemicarbazone, the L-2 complexes utilize the ONN set. The reaction of L-4 and the nickel salt gave the L-3 complex by loss of the CH3 group from the sulphur. The complexes were characterized by physico-chemical and spectroscopic methods. The structures of the L-1 and L-2 complexes have been determined by single crystal X-ray diffraction and a new coordination mode (ONN) of salicylaldehyde thiosemicarbazones has been identified. Research Fund of Istanbul UniversityIstanbul University [T-957/06102006] This work was supported by the Research Fund of Istanbul University. Project No. T-957/06102006.

Binuclear copper(II) complexes of thiosemicarbazones derived from cuminaldehyde (p-isopropyl benzaldehyde) and substituted thiosemicarbazides NH2NHC(S)NHR, where R = H, Me, Et or Ph have been synthesized and characterized. The ESR indicates that the dissociation of dimeric complex into mononuclear [Cu(L)Cl(DMSO)3] units in polar solvents like DMSO, where L = monoanionic thiosemicarbazone. The molecular ion peak in the LC-MS coincides with the formula weight of the complexes. The absorption titration studies revealed that each of these complexes is an avid binder to calf thymus-DNA. The apparent binding constants are in the order of 107–108 M−1. The nucleolytic cleavage activities of the ligands and their complexes were assayed on pUC18 plasmid DNA using gel electrophoresis in the presence and absence of H2O2. The ligands showed increased nuclease activity when administered as copper complexes. All these copper(II) complexes behave as an efficient chemical nucleases with hydrogen peroxide activation. These studies revealed that the complexes exhibit both oxidative and hydrolytic chemistry in DNA cleavage.

The monobasic bidentate Schiff base complexes of palladium(II) and platinum(II) derived from 1H-indol-2,3-dione thiosemicarbazone (L1H) and 1H-indol-2,3-dione semicarbazone (L2H) have been characterized on the basis of elemental analysis, molecular weight determinations, i.r., 1H n.m.r. and u.v. spectral studies. Based on these studies a square planar environment around the metal atoms has been proposed. Antimicrobial effects of both the ligands and their complexes on different species of pathogenic fungi and bacteria have been recorded and these are found to possess significant fungicidal and bactericidal properties.

During the condensation of 4-methyl-4-phenyl-3-thiosemicarbazide (3) with 2,3-butanedione an unexpected by-product, 8a-methyl-6,8a-dihydro-8-methyl-2-[N-methyl-N-phenylamino]-5H-1,3,4-thiadiazolo[3,2-d][1,2,4]triazine-5-thione, (5) was obtained in addition to the desired bis(thiosemicarbazone) (4). An X-ray crystal structure was obtained and is presented together with a proposed mechanism for its formation. A brief investigation of the coordination chemistry of bicycle (5) was carried out. The formation of cyclic compounds during the synthesis of analogues with extended backbones is also described.

New iron(III) complexes of 5-methyl-3-formylpyrazole 3-hexamethyleneiminylthiosemicarbazone (HMPz3Hex), [Fe(MPz3Hex)2]X · nH2O (where X = Cl, NO3or ClO4 and n = 1–2) have been synthesized and physico-chemically characterized by magnetic data (polycrystalline state), electronic, i.r. and e.p.r. spectral studies. The reported complexes are all cationic electrolytes (1:1) containing two moles of monodeprotonated title ligand and an anionic counterpart. I.r. spectra (4000–200 cm−1) indicate coordination to the central iron(III) ion via the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulphur atoms of the primary ligand molecule. E.p.r. data (r.t. and l.n.t.) show the presence of a low-spin iron(III) cation with d 2 d 2 d 1 configuration. Cyclic voltammograms of iron(III) complexes indicate a reversible Fe+3/Fe+2 couple. X-ray data of [Fe(MPz3Hex)2]ClO4 · 2H2O (P1, triclinic) authenticate a FeN4S2 distorted octahedral coordination with the two azomethine nitrogens trans to each other; the pyrazolyl nitrogens and thiolato sulphurs are in cis-positions, indicating an unusual rotation about the azomethine (C=N) double bond of the free HMPz3Hex during complexation with iron(III).

A new NiII complex of 5,6-dihydro-2H-pyran-3-aldehyde thiosemicarbazone (HDPTSC) has been synthesized and characterized by microanalyses, magnetic susceptibility, molar conductance measurements and by spectral methods (i.r., u.v.–vis., 1H-n.m.r.). The structure of [Ni(DPTSC)2] · B DMF has been solved using X-ray diffraction and found to be highly symmetrical with a trans -arrangement of the two bidentate ligands. The thiosemicarbazone coordinates as an anionic ligand via the thiosemicarbazone moiety’s azomethine nitrogen and thiolate sulfur [on loss of the N2 hydrogen]. The electrochemical behavior of the ligand and its NiII complex, determined by cyclic voltammetry, shows that the redox process of the ligand was highly irreversible, whereas the redox process of the NiII complex was observed as a one electron transfer process in a quasi-reversible and diffusion-controlled reaction.

2,6-Diformylpyridine bis(N4-methylthiosemicarbazone) and bis(N4-dimethylthiosemicarbazone), H22,6Fo4M and H22,6Fo4DM, respectively, and 2,6-diacetylpyridine bis(N4-methylthiosemicarbazone) and bis(N4-dimethylthiosemicarbazone), H22,6Ac4M and H22,6Ac4DM, and their copper(II) and nickel(II) complexes have been synthesized. The 1H-n.m.r. spectra of the free bis(thiosemicarbazones) show that, most often, one of the thiosemicarbazone moieties is hydrogen bonded to the pyridine nitrogen, and in [2H6]-DMSO there is interaction with solvent oxygen. Golden yellow H22,6Ac4DM has a bifurcated hydrogen bonding interaction by one of the thiosemicarbazone moieties resulting in conjugation. Coordination to copper(II) and nickel(II) centers is via the pyridine nitrogen, amine nitrogen and thiolato sulfur and most of the complexes formed are polynuclear with thiosemicarbazone moieties from the same ligand coordinating to different metal centers.

A thiosemicarbazone derivative of the Vitamin K3 has been synthesized. Five transition metal complexes of the thiosemicarbazone have been prepared and characterized by i.r., u.v.–vis., molar conductance and thermal analyses. All of the complexes possess strong inhibitory action against G(+) Staphylococcus aureus, G(−) Hay bacillus, and G(−) Eschericha coli. The antibacterial activities of the complexes are stronger than those of the thiosemicarbazone itself.

CoII,III, NiII, and CuII complexes of new dehydroacetic acid N4-substituted thiosemicarbazones have been studied. The substituted thiosemicarbazones, N4-dimethyl-(DA4DM), N4-diethyl-(DA4DE), 3-piperidyl-(DApip) and 3-hexamethyleneiminyl-(DAhexim), when reacted with the metal chlorides, produced two CoII complexes, [Co(DA4DE)Cl2] and [Co(DAhexim)2Cl2]; two CoIII complexes, [Co(DA4DM-H)2Cl] and [Co(DApip-H)(DApip-2H)]; a paramagnetic NiII complex, [Ni(DAhexim)(DAhexim-H)Cl]; three diamagnetic NiII complexes, [Ni(DA4DM-H)Cl], [Ni(DA4DE-H)Cl] and [Ni(DApip-H)Cl]; and four CuII complexes with the analogous stoichiometry of the latter three NiII complexes. These new thiosemicarbazones have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The metal complexes have been characterized by i.r. and electronic spectra, and when possible, n.m.r. and e.s.r. spectra, as well as elemental analyses, molar conductivities, and magnetic susceptibilities. The crystal and molecular structure of the four-coordinate CuII complex, [Cu(DAhexim-H)Cl] has been determined by single crystal X-ray diffraction and the anionic ligand coordinates via an oxygen of the dehydroacetic acid and the thiosemicarbazone moiety's imine nitrogen and thione sulfur.

The synthesis of CoII, NiII, CuII and CdII complexes of 2-furfural 4-phenyl semicarbazone (FPSC) with stoichiometric formulae: [M(FPSC)2X2] (M = Co, Ni or Cu; X = Cl or Br), [CuCl2(FPSC)] and [(CdCl2)2(FPSC)] has been obtained for the first time. The complexes were characterized by elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra. FPSC is deduced to act as a bidentate ligand in the CoII, NiII and CuII complexes and as a tetradentate one in [(CdCl2)2(FPSC)].

New ruthenium(II) complexes, [Ru(CO)(B)(LL′)(PPh3)] (where, LL′ = tridentate Schiff bases; B = PPh3, pyridine, piperidine or morpholine) have been prepared by reacting [RuHCl(CO)(PPh3)3] or [RuHCl(CO)(PPh3)2(B)] with Schiff bases containing donor groups (O, N, X) viz., salicylaldehyde thiosemicarbazone (X = S), salicylaldehyde semicarbazone (X = O), o-hydroxyacetophenone thiosemicarbazone (X = S) and o-hydroxyacetophenone semicarbazone (X = O). The new complexes were characterised by elemental analysis, spectral (i.r., 1H- and 31P-n.m.r.), data.

Metal complexes of a new thiosemicarbazone derived from 3-acetylumbelliferone (HL) have been prepared and characterized. The complexes have the general formula ML2 · nH2O where MII = Co, Ni, Cu and Zn; n = 0 and 2. The ligand and its complexes have been studied for their possible antitumour activity against HL-60 human leukemia in vitro.

The chiral (ONS) dianionic Schiff base ligand benzoin thiosemicarbazone (H2L) reacts with MoO2(acac)2 to give the polymeric complex [(MoO2L) n ] (1) (Type 1). The reaction of MoO2L with pyridine (py), 3-picoline (3-pic) or 4-picoline (4-pic) gives [MoVIO2LD] (D = py, 3-pic or 4-pic) (Type 1). Further, the reaction of [MoO2L] or [MoO2LD] with PPh3 or reaction of [MoO2L] with PPh3 (plus bpy or phen, D) in the presence of donor reagents D gives [MoIVOL] or [MoIVOLD] (Type 2). On the other hand, the reaction of [MoO2L] with hydrazides (zdhH3) such as benzoylhydrazine (bhH3), isonicotinoylhydrazine (inhH3), nicotinoylhydrazine (nhH3), salicyloylhydrazine (slhH3) and thiosemicarbazide (tscH3) produced non-oxo–diazenido complexes [MoL(zdh)] (Type 3). The complexes have been characterized by elemental analyses, molar conductance, magnetic moment, electronic, i.r. and e.s.r. spectroscopic measurements.

New ruthenium(II) complexes with 2-hydroxybenzophenone N(4)-substituted (Me, Ph and/or piperidyl) thiosemicarbazones have been prepared and characterised by elemental analysis, molar conductivity, thermal analysis, spectroscopy (i.r., 1H-n.m.r. and u.v.–vis.) and by cyclic voltammetry. The thiosemicarbazones coordinate to ruthenium(II) as mononegative tridentate ligands via the deprotonated hydroxyl group, N1 nitrogen and thione sulphur centres. The redox properties, nature of the electrode processes and the stability of the complexes towards oxidation in CH2Cl2 are discussed. The change in the E 1/2 values of the complexes can be related to the basicity of the N(4)-substituents. All the complexes display an irreversible one-electron charge-transfer couple in the potential range studied.

New picoline adducts with carbamic acid [(furan-2-yl)methylene]hydrazide–CuII (CFMH) (1); thiocarbamic acid [(furan-2-yl)methylene]hydrazide–CuII (TFMH) (2); carbamic acid [(furan-2-yl)ethylidene]hydrazide–CuII (CFEH) (3), thiocarbamic acid [(furan-2-yl)ethylidene]hydrazide–CuII (TFEH) (4); carbamic acid [(thiophene-2-yl) methylene]hydrazide–CuII (CTMH) (5), thiocarbamic acid [(thiophene-2-yl)methylene]hydrazide–CuII (TTMH) (6), carbamic acid [(thiophene-2-yl)ethylidene]hydrazide–CuII (CTEH) (7), thiocarbamic acid [(thiophene-2-yl)ethylidene]hydrazide–CuII (TTEH) (8) have been prepared and characterized by analytical, i.r., electronic, e.s.r. and c.v. spectral data. The electronic spectra suggest distorted octahedral geometry for all the picoline adducts. E.s.r. g ∥ values lie between 2.251–2.286 at l.n.t. All the adducts undergo a quasi-reversible one-electron reduction in the range +0.47 to +0.51 V versus s.c.e., attributable to the CuIII/CuII redox couple. The electron transfer is much faster in the semicarbazone complexes than in the thiosemicarbazone complexes. All adducts showed increased nuclease activity in the presence of oxidant; the nuclease activity is compared with that of the parent copper(II) complexes.

Cobalt(II), nickel(II) and copper(II) complexes of two new bis(di-2-pyridyl ketone) dithiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. The bis(di-2-pyridyl ketone) dithiosemicarbazones were prepared from dithiosemicarbazides derived from piperazine and N,N′-dimethylethylenediamine. N.m.r., i.r., and electronic spectra of the dithiosemicarbazones and their complexes along with e.s.r. spectra of the copper(II) complexes have been recorded. The complexes are bi-, tri- and tetranuclear and involve the dithiosemicarbazones coordinating as dianionic, anionic and neutral ligands.

Copper(II) Schiff base complexes derived from furan-2-carboxaldehyde, 2-furylmethyl ketone, thiophene-2-carboxaldehyde and methyl-2-thienyl ketone with semicarbazide and thiosemicarbazide have been prepared and characterized by analytical, i.r., electronic, e.s.r. and c.v. spectral data. The electronic spectral d–d band position varies from 744–415 nm in pyridine and 872–371 nm in DMF. E.s.r. g∥ values lie between 2.1439 and 2.3149 at LNT. All complexes undergo quasi-reversible one-electron electrochemical reduction (CuIII/CuII) in the 0.42–0.52 V potential range. The electron transfer is much faster in thiosemicarbazone complexes compared to semicarbazone complexes. All these copper(II) complexes showed increased nuclease activity in presence of oxidant.

New iron(III) complexes of 5-methyl-3-formylpyrazole thiosemicarbazone (HMPzTS) and 5-methyl-3-formylpyrazole-4-phenylthiosemicarbazone (HMPzPTS), namely [Fe(MPzTS)2]X and [Fe(MPzPTS)2]X respectively, where X=Cl, NO3, SCN and ClO4, have been synthesised and physico-chemically characterised by magnetic measurements (polycrystalline state), electronic, i.r., e.s.r. and Mossbauer spectra. All are cationic complexes containing two monoprotonic tridentate ligands with NNS donor sites and an anionic counterpart; they behave as 1:1 electrolytes in MeOH/DMF. Coordination to central iron(III) via the pyrazolyl nitrogen (2N), the azomethine nitrogen and the thiolato sulphur atom is confirmed in the complexes from i.r. data. E.s.r. data (RT & LNT) reveal the presence of a spin-paired iron(III) cation with d2xyd2yzd1xy configuration. The 57Fe Mossbauer spectral data (RT) are commensurate with the presence of two iron(III) spin states, the percentage of each being dependent upon the counterion of the species.

The synthesis and characterization of CoII, NiII, CuII and CdII complexes with 2-furfuralsemicarbazone (FSC) and 5-methyl 2-furfuralsemicarbazone (MFSC) are reported. These ligands lead to the complexes: [ML2X2] or [MLX2] (L = FSC or MFSC) whose structures were determined using elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra as well as by n.m.r. FSC and MFSC act as bidentate ligands in most of the CoII, NiII, CuII and CdII complexes. MFSC is a monodentate ligand in [NiBr2(MFSC)4].

Cobalt(II) complexes with 2-aminoacetophenone thiosemicarbazone and three N(4)-substituted thiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. I.r. and electronic spectra of the thiosemicarbazones and their complexes, along with physical properties of the complexes, have been obtained. The 2-aminoacetophenone thiosemicarbazones coordinate both as neutral and anionic ligands via the thiosemicarbazone moiety's imine nitrogen and thione/thiolato sulfur [on loss of the N(2) hydrogen].

Nickel(II) complexes with five 4-acetamidobenzaldehyde N(4)- substituted thiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. N.m.r., i.r. and electronic spectra of the thiosemicarbazones and their complexes, along with physical properties of the complexes, have been recorded. These thiosemicarbazones coordinate as anionic ligands via the thiosemicarbazone moiety's azomethine nitrogen and thiolate sulfur [upon loss of the N(2) hydrogen] when reacted with NiCl2 in the presence of Et3N or with Ni(OAc)2.

Seven platinum(II) complexes isolated from thiosemicarbazones derived from 2-, 3- and 4-formylpyridine and 2-, 3-, and 4-acetylpyridine have been characterised by microanalyses, molar conductivities and by their i.r. and 1H-n.m.r. spectra.

Nickel(II), copper(II), zinc(II), and cadmium(II) complexes of 1-phenylglyoxal bis{N(4)-ethylthiosemicarbazone} have been synthesized and characterized spectroscopically. The bis(thiosemicarbazone) and its diamagnetic complexes have been characterized by their melting points, i.r., electronic, mass and 1H n.m.r. spectra. The four-coordinate copper(II) complex was also studied by e.s.r. spectroscopy. Upon coordination, the loss of a proton from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazone) coordinates to nickel(II) and copper(II) as a dianionic, tetradentate N2S2 ligand; but for zinc(II) and cadmium(II), mass spectral results suggest the formation of binuclear complexes.

The proton–ligand stability constants of α-pyridoin thiosemicarbazone, α-pyridoin 2–methylthiosemicarbazone, α-pyridoin 4–methylthiosemicarbazone and α-pyridoin (4–phenylthiosemicarbazone) as well as the formation constants of their chelates with CuII, NiII, CoII, ZnII and MnII have been determined. The Calvin–Bjerrum pH titration techniques, as modified by Irving and Rossotti, were employed in aqueous media at different ionic strengths and temperatures. The stability constants of the complexes follow the order: CuII > NiII > CoII > ZnII >MnII which is in accord with the Irving–Williams series. The chelates derived from α-pyridoin 4–phenylthiosemicarbazone have relatively higher stability constants, which may be attributed to the presence of the benzene ring in the chain.

Mononuclear copper(II) complexes with 2-aminoacetophenone thiosemicarbazone and three N(4)-substituted thiosemicarbazones have been prepared in ethanolic solution and characterized by physical and spectral methods. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic, and 1H- and 13C-n.m.r. spectra of the thiosemicarbazones, have been obtained. The 2-aminoacetophenone thiosemicarbazones coordinate as neutral ligands via the thiosemicarbazone moiety's azomethine nitrogen and thione sulfur, except for the piperidylthiosemicarbazone, which undergoes deprotonation and coordinates via the thiolato sulfur, as well as through the azomethine nitrogen. Complexes formed in the presence of triethylamine also form complexes with the anionic form of these thiosemicarbazones.

Copper(II) and nickel(II) complexes of glyoxaldehyde bis{N(3)-methyl-, bis{N(3)-ethyl-, bis{N(3)-dimethyl-, bis{piperidyl- and bis{hexamethyleneiminylthiosemicarbazone} have been prepared and studied spectroscopically. The five bis(thiosemicarbazones) have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The four-coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by a number of the spectroscopic techniques mentioned above. Upon formation of these complexes, loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands.

Copper(II) and nickel(II) complexes of phenylglyoxal and phenylpropane-1,2-dione bis{N(3)-methyl-, bis{N(3)-dimethyl-, bis{piperidylthiosemicarbazone} have been prepared and studied spectroscopically. The six bis(thiosemicarbazones) have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The four-coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by spectroscopic techniques mentioned above. Upon formation of these complexes, the loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands.

Cobalt(III) complexes of acetyl- and formylpyrazine N(4)-substituted thiosemicarbazones have been synthesized and characterized by spectral and physical techniques. The crystal structure of the bis{formylpyrazine N(4)-methylthiosemicarbazone}cobalt(III) complex shows the two ligands coordinated in a mer-configuration, and the orientation of the thiosemicarbazone moiety's N(4)-methyl is Z with respect to the thiolato sulfur in both ligands. Included is the crystal structure of the bis- {2-acetylpyridineN(4)-propylthiosemicarbazone}cobalt(III) complex in which the two thiosemicarbazone ligands are also in the mer-configuration, but one ligand has the propyl group oriented Z with respect to the thiolato sulfur and the other E. Both complexes' bond lengths and bond angles are compared with other cobalt(III) thiosemicarbazone complexes.

Copper(II) complexes between three 4-formylantipyrine N(4)-substituted thiosemicarbazones and four copper(II) salts have been prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic and 1H and 13C-n.m.r. spectra of the thiosemicarbazones, have been obtained. Both mononuclear and binuclear complexes have been formed with bridging ligands for the latter, being either chloro or acetato. The stoichiometries of the complexes are dependent on both the steric requirements of the thiosemicarbazone ligands and the electronic effects of their N(4)-substituents.

Ruthenium(II) heptacoordinate complexes containing the pentadentate SNNNS chelating ligand 2,6–diacetylpyridine bis(4–(p-tolyl)thiosemicarbazone) (L1H2) have been prepared. The compounds were of the type Ru(L1H2)X2 [X=Cl (1);Br (2); SCN (3)],[Ru(L1H2)- (Y)Cl]Cl [Y=imidazole (4); pyridine-N-oxide (5)] and [Ru(L1H2)(PPh3)X]Y, [X=Cl (6), (7);Br (8); Y=ClO4/ PF6]. The complexes were characterised by i.r., u.v.–vis. and n.m.r. spectroscopy and their electrochemical behaviour was examined by cyclic voltammetry. They exhibit a reversible to quasi-reversible RuII/RuIII couple in MeCN solution at a glassy carbon working electrode using an Ag/AgCl electrode as the reference.

Heterocyclic base adducts of salicylaldehyde N(4)- cyclohexylthiosemicarbazone(H2L) copper(II) complexes have been synthesized and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic and 1H- and 13C-n.m.r. spectra of the thiosemicarbazone have been obtained. Based on e.s.r. studies, all possible parameters have been calculated. The g values, calculated for all the complexes in frozen solution, indicate the presence of the unpaired electron in the dx2−y2 orbital. The metal–ligand bonding parameters evaluated showed strong in-plane σ- and in-plane π-bonding. The magnetic and spectroscopic data indicate a square-planar geometry for the four-coordinate and a distorted square-pyramidal structure for the five-coordinate complexes. From cyclic voltammetric data quasireversible copper(II)/copper(I) couples are observed for the complexes.

Copper(II) complexes of 6-methyl-2-formylpyridine thiosemicarbazone, and its 4N-methyl-, 4N-ethyl-, 4N-phenyl-,4 N-dimethyl-, 4N-diethyl-, 4N-dipropyl-, 3-pyrrolidinyl, 3-piperidinyl- and 3-hexamethyleneiminylthiosemicarbazone derivatives were prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as 1H and 13C n.m.r. spectra of the thiosemicarbazones, were obtained. The thiosemicarbazones and their copper(II) complexes show either modest or no growth inhibitory activity against Aspergillus niger, but the 4N-dialkyl- and 3-azacyclo-derivatives exhibit considerable activity against Paecilomyces variotii.

The preparation and spectral properties of five copper(II) complexes of semicarbazones, derived from 2-hydroxy-naphthaldehyde (NPSCZ), benzoin (BZSCZ) and isatin (ISSCZ) are described. I.r., electronic, e.s.r. 1H and 13C n.m.r. spectra show that the semicarbazone's coordination is distorted trigonal bipyramidal for [Cu(BZSCZ-2H)(H2O)], distorted tetragonal pyramidal for [Cu(NPSCZ)2](ClO4)2 and dimeric for the other three complexes.