New mononuclear organotin(IV) 4-benzhydrylpiperazine-1-carbodithioates: Synthesis, spectroscopic characterization, X-ray structures and in vitro antimicrobial activities

A new series of organotin(IV) complexes with 4-benzhydrylpiperazine-1-carbodithioate (L) were synthesised by the metathesis reactions of the ligand-salt with triorganotin(IV) chlorides and diorganotin(IV) dichlorides in the appropriate molar ratio. All the complexes were characterized by elemental analysis, Raman, IR, and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy. Solid-state studies (Raman, IR and X-ray analysis) confirmed the bidentate coordination of the ligand in all cases. Multinuclear NMR spectroscopy suggested that some tri- and diorganotin complexes reduce their geometry by one unit in solution. The τ values, 0.6 and 0.24 for chlorodibutyl- and chlorodiethyltin(IV) derivatives, respectively, authenticated the trigonal bipyramidal geometry for the first complex and distorted square-pyramidal geometry for the latter. The low τ value for the chlorodiethyltin(IV) complex is attributed to the additional Sn···Cl and Sn···S intermolecular interactions. The antimicrobial results indicated the compounds are active biologically.     

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.     

Synthesis, spectroscopic characterization and biological activity on newly synthesized copper(II) and nickel(II) complexes incorporating bidentate oxygen-nitrogen hydrazone ligands

We report the synthesis of the hydrazone ligands, 1-(phenyl-hydrazono)-propan-2-one (PHP), 1-(p-tolyl-hydrazono)-propan-2-one (THP), 1-[(4-chloro-hydrazono)]-propan-2-one (CHP), and their Ni(II) and Cu(II) metal complexes. The structure of the ligands and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, UV, and EPR) measurements. IR spectra indicate that the free ligands exist in the hydrazo-ketone rather than azo-enol form in the solid state. Also, the hydrazo-NH exists as hydrogen bonded to the keto-oxygen either as intra or as intermolecular hydrogen bonding. In all the studied complexes, all ligands behave as a neutral bidentate ligands with coordination involving the hydrazone-nitrogen and the keto-oxygen atoms. The magnetic and spectral data indicate a square planar geometry for Cu²⁺ complexes and an octahedral geometry for Ni²⁺ complexes. The ligands and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. It may be concluded that the antimicrobial activity of the compounds is related to cell wall structure of bacteria.Protonation constant of (PHP) ligand and stability constants of its Cu²⁺ and Ni²⁺ complexes were determined by potentiometric titration method in aqueous solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the hydrazone ligand (PHP) titrated here has one protonation constant. The divalent metal ions Cu²⁺ and Ni²⁺ form with (PHP) 1:1 and 1:2 complexes. The insolubility of (THP) and (CHP) ligands in aqueous medium does not permit the determination of their protonation constants and formation constants of the corresponding complexes in aqueous solution.     

Antimicrobial,spectral, magnetic and thermal studies of Cu(II), Ni(II), Co(II), UO2(VI) and Fe(III) complexes of the Schiff base derived from oxalylhydrazide

The Schiff base ligand, oxalic bis[(2-hydroxybenzylidene)hydrazide], H₂L, and its Cu(II), Ni(II), Co(II), UO₂(VI) and Fe(III) complexes were prepared and tested as antibacterial agents. The Schiff base acts as a dibasic tetra- or hexadentate ligand with metal cations in molar ratio 1:1 or 2:1 (M:L) to yield either mono- or binuclear complexes, respectively. The ligand and its metal complexes were characterized by elemental analyses, IR, ¹H NMR, Mass, and UV-Visible spectra and the magnetic moments and electrical conductance of the complexes were also determined. For binuclear complexes, the magnetic moments are quite low compared to the calculated value for two metal ions complexes and this shows antiferromagnetic interactions between the two adjacent metal ions. The ligand and its metal complexes were tested against a Gram + ve bacteria (Staphylococcus aureus), a Gram -ve bacteria (Escherichia coli), and a fungi (Candida albicans). The tested compounds exhibited high antibacterial activities.     

In-vitro antibacterial,antifungal activity of some transition metal complexes of thiosemicarbazone Schiff base (HL) derived from N4-(7′-chloroquinolin-4′-ylamino) thiosemicarbazide

The synthetic, spectroscopic, and biological studies of Cu(II), Ni(II), Zn(II), Co(II), Mn(II), Fe(III) and Cr(III) complexes of N⁴-(7′-chloroquinoline-4′-ylamino)-N¹-(2-hydroxy-benzylidene)thiosemicarbazone (HL) obtained by the reaction of N⁴-(7′-chloroquinolin-4′-ylamino)thiosemicarbazide with 2-hydroxybenzaldehyde. The structures of the complexes were determined on the basis of the elemental analyses, spectroscopic data (IR, electronic, ¹H and ¹³C NMR and Mass spectra) along with magnetic susceptibility measurements, molar conductivity and thermogravimetric analyses. Electrical conductance measurement revealed the non-electrolytic nature of the complexes. The resulting colored products are mononuclear in nature. On the basis of the above studies, only one ligand was suggested to be coordinated to each metal atom by thione sulfur, azomethine nitrogen and phenolic oxygen to form mononuclear complexes in which the thiosemicarbazone behaves as a monobasic tridendate ligand. The ligand and its metal complexes were tested against Gram + ve bacteria (Staphylococcus aureus), Gram ? ve bacteria (Escherichia coli), fungi (Candida albicans) and (Fusarium solani). The tested compounds exhibited significant activity.     

Synthesis, characterization and biological studies of organotin(IV) complexes with hydrazone ligand

Four organotin(IV) complexes with general formula [RSnCl_n−1(TCB)] [R = Ph₂, n = 2 (2); R = Me, n = 3 (3); R = Bu, n = 3 (4); R = Ph, n = 3 (5)] have been synthesized by direct reaction of thiophene-2-carboxaldehyde benzhydrazone ligand [HTCB, (1)], base and organotin(IV) chloride in absolute methanol under N₂ atmosphere. All organotin(IV) complexes were characterized by elemental analyses, molar conductivity, UV-Vis, FT-IR, ¹H and ¹³C NMR spectral studies. Among them, diphenyltin(IV) complex (2) has also been characterized by X-ray crystallography diffraction analyses. The cytotoxicity of the hydrazone ligand as well as its organotin(IV) complexes (2-5) were determined with Artemia salina. While no-choice bioassay was employed on Coptotermes sp. to evaluate the termiticidal effect of all the complexes. Besides, the ligand (1) and its organotin(IV) complexes (2-4) were also tested against five types of bacteria namely Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi.     

Novel bis(carboxylato)dichlorido(ethane-1,2-diamine)platinum(IV) complexes with exceptionally high cytotoxicity

(OC-6-33)-Dichlorido(ethane-1,2-diamine)dihydroxidoplatinum(IV) (1) was carboxylated using succinic- or 3-methylglutaric anhydride. The resulting bis(carboxylato)platinum(IV) complexes display free, uncoordinated carboxylic acid groups which were further derivatized with primary aliphatic alcohols. The complexes were characterized in detail by elemental analysis, ESI-MS, FT-IR, as well as multinuclear (¹H, ¹³C, ¹⁵N, ¹⁹⁵Pt) NMR spectroscopy. Cytotoxic properties were evaluated in four human tumor cell lines originating from ovarian carcinoma (CH1, SK-OV-3), cervical carcinoma (HeLa) and colon carcinoma (SW480) by means of the MTT assay (MTT = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide). Structure-activity relationships showed that the cytotoxicity increased with increasing lipophilicity of the alcoholate moiety yielding IC₅₀ values in the low micromolar or even low nanomolar range.     

Sensitivity to vinyl phenol derivatives produced by phenolic acid decarboxylase activity in Escherichia coli and several food-borne Gram-negative species

Ferulic, p-coumaric, and caffeic acids are phenolic acids present in soil, food, and gut, which have antimicrobial effects. Some Gram (+) bacteria metabolize these phenolic acids into vinyl derivatives due to phenolic acid decarboxylase activity (PAD) involved in the phenolic acid stress response (PASR). In this study, the antimicrobial activity of phenolic acids and their vinyl derivatives was tested on a panel of desirable and undesirable food-borne bacteria, especially Gram (?) species of Salmonella, Enterobacter, Klebsiella, and Pseudomonas, most of them without PAD activity. Native and engineered Escherichia coli strains either expressing or not PAD activity were included. Gram (?) bacteria of the panel were not significantly inhibited by phenolic acids at 3 mM, but were dramatically inhibited by the corresponding vinyl derivatives. On the contrary, Gram (+) bacteria displaying the PASR face the toxicity of phenolic acids by PAD activity and are not inhibited by vinyl phenols. In E. coli, the genes aaeB and marA, encoding efflux pumps for antimicrobial compounds, are upregulated by the addition of p-coumaric acid, but not by its derivative 4-vinyl phenol (p-hydroxystyrene). These results suggest that phenolic acids and their vinyl phenol derivatives produced by PAD (+) species could have a significant impact on undesirable or pathogenic food-borne Gram (?) bacteria in complex microbial ecosystems.     

Synthesis, characterization and antimicrobial activity of new silver complexes with N-heterocyclic carbene ligands

Synthesis, structure, and antimicrobial studies of silver complexes of N-heterocyclic carbene (NHC) are reported. All the silver-NHC complexes (1a-f) were prepared from the benzimidazolium salts by the reactions with Ag₂O in dichloromethane as a solvent at room temperature. The new compounds characterized by ¹H NMR, ¹³ C NMR, IR and elemental analysis techniques which support the proposed structures. Chloro[1-(2,4,6-trimethylbenzyl)-3-(methoxyethyl)benzimidazol-2-ylidene]silver(I) complex was structurally characterized by single-crystal X-ray diffraction. A series of new Ag-NHC complexes were screened for their in vitro antimicrobial activity against a variety of Gram-positive and Gram-negative bacteria as well as for their antifungal activity against a Candida albicans and Candida tropicalis.     

7-Alkyl-N(2)-substituted-3-deazaguanines. Synthesis, DNA polymerase III inhibition and antibacterial activity

Several 2-anilino- and 2-benzylamino-3-deaza-6-oxopurines [3-deazaguanines] and selected 8-methyl and 8-aza analogs have been synthesized. 7-Substituted N²-(3-ethyl-4-methylphenyl)-3-deazaguanines were potent and selective inhibitors of Gram+ bacterial DNA polymerase (pol) IIIC, and 7-substituted N²-(3,4-dichlorobenzyl)-3-deazaguanines were potent inhibitors of both pol IIIC and pol IIIE from Gram+ bacteria, but weakly inhibited pol IIIE from Gram− bacteria. Potent enzyme inhibitors in both classes inhibited the growth of Gram+ bacteria (MICs 2.5-10 μg/ml), and were inactive against the Gram− organism Escherichia coli. Several derivatives had moderate protective activity in Staphylococcus aureus-infected mice.     

Preparation and spectroscopic properties of oxovanadium(IV) and dioxomolybdenum(VI) complexes with tetraaza[14]annulenes containing pyridine rings

The reaction of 5,14-dihydro-7,16-diethyl-(E)- or -(Z)-dipyrido [b, i] [ 1,4,8,11 ] tetraazacyclotetradecine with vanadium(III) chloride led to the corresponding oxovanadium(IV) complexes, while reaction with tetracarbonylbis(piperidine)molybdenum(O) gave the corresponding dioxomolybdenum(VI) complexes. The oxovanadium(IV) complexes showed mass spectra with prominent parent peaks in the El mode. On the other hand the FD mass spectra for the dioxomolybdenum(VI) complexes exhibited the expected parent and parent-O peaks. A VO stretching band was observed at ca. 970 cm⁻¹ for the oxovanadium(IV) complexes. The dioxomolybdenum(VI) complexes had strong bands at 855 and 885 cm⁻¹ in the NaCl region, which are attributable to the MoO symmetric and asymmetric stretching modes. The absorption bands observed above 20 000 cm⁻¹ range were attributed to the CT and π→π^* transitions. Judging from the spin Hamiltonian parameters, the oxovanadium(IV) complexes are of square-planar types with an unpaired electron in the d_xy orbital. The downfield shifts for the dioxomolybdenum(VI) complexes are much larger in magnitude than those observed for the corresponding oxochromium(IV) complexes. This is primarily dependent on the fact that the magnitude of the positive charge fed by molybdenum(VI) is greater than that by chromium(IV).     

Synthesis and Antimicrobial Evaluation of Novel Chiral 2‐Amino‐4,5,6,7‐tetrahydrothieno[2,3‐c]pyridine Derivatives

New N‐substituted‐2‐amino‐4,5,6,7‐tetrahydrothieno[2,3‐c]pyridine derivatives were synthesized employing a convenient one‐pot three‐component method and their structures were characterized by ¹H‐NMR and single crystal X‐ray diffraction analysis. All the synthesized compounds were in vitro screened for antimicrobial activity against Gram‐positive (Sarcina lutea) and Gram‐negative bacteria (Escherichia coli). In this work, we introduced a chiral residue on the tetrahydropyridine nitrogen, the hitherto the less investigated position on this pharmacophore in order to explore the effect. The antibacterial results showed that the synthesized compounds were active only against Gram‐positive bacteria and the (R)‐enantiomers displayed a greater antimicrobial potency than their (S)‐counterparts. The structure–activity relationship here investigated may provide some interesting clues for future development of tetrahydrothienopyridine derivatives with higher antimicrobial activity.     

An in vitro comparative assessment with a series of new triphenyltin(IV) 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoates endowed with anticancer activities: structural modifications, analysis of efficacy and cytotoxicity involving human tumor cell lines

Four new triphenyltin(IV) complexes of composition Ph₃SnLH (where LH = 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoate) (1-4) were synthesized and characterized by spectroscopic (¹H, ¹³C and ¹¹⁹Sn NMR, IR, ¹¹⁹Sn Mössbauer) techniques in combination with elemental analysis. The ¹¹⁹Sn NMR spectroscopic data indicate a tetrahedral coordination geometry in non-coordinating solvents. The crystal structures of three complexes, Ph₃SnL¹H (1), Ph₃SnL³H (3), Ph₃SnL⁴H (4), were determined. All display an essentially tetrahedral geometry with angles ranging from 93.50(8) to 124.5(2)°; ¹¹⁹Sn Mössbauer spectral data support this assignment. The cytotoxicity studies were performed with complexes 1-4, along with a previously reported complex (5) in vitro across a panel of human tumor cell lines viz., A498, EVSA-T, H226, IGROV, M19 MEL, MCF-7 and WIDR. The screening results were compared with the results from other related triphenyltin(IV) complexes (6-7) and tributyltin(IV) complexes (8-11) having 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoates framework. In general, the complexes exhibit stronger cytotoxic activity. The results obtained for 1-3 are also comparable to those of its o-analogs i.e. 4-7, except 5, but the advantage is the former set of complexes demonstrated two folds more cytotoxic activity for the cell line MCF-7 with ID₅₀ values in the range 41-53 ng/ml. Undoubtedly, the cytotoxic results of complexes 1-3 are far superior to CDDP, 5-FU and ETO, and related tributyltin(IV) complexes 8-11. The quantitative structure-activity relationship (QSAR) studies for the cytotoxicity of triphenyltin(IV) complexes 1-7 and tributyltin(IV) complexes 8-11 is also discussed against a panel of human tumor cell lines.     

In vitro activity of novel in silico‐developed antimicrobial peptides against a panel of bacterial pathogens

Antimicrobial‐peptide‐based therapies could represent a reliable alternative to overcome antibiotic resistance, as they offer potential advantages such as rapid microbicidal activity and multiple activities against a broad spectrum of bacterial pathogens. Three synthetic antimicrobial peptides (AMPs), AMP72, AMP126, and also AMP2041, designed by using ad hoc screening software developed in house, were synthesized and tested against nine reference strains. The peptides showed a partial β‐sheet structure in 10‐mM phosphate buffer. Low cytolytic activity towards both human cell lines (epithelial, endothelial, and fibroblast) and sheep erythrocytes was observed for all peptides. The antimicrobial activity was dose dependent with a minimum bactericidal concentration (MBC) ranging from 0.17 to 10.12 μM (0.4–18.5 µg/ml) for Gram‐negative and 0.94 to 20.65 μM (1.72‐46.5 µg/ml) for Gram‐positive bacteria. Interestingly, in high‐salt environment, the antibacterial activity was generally maintained for Gram‐negative bacteria. All peptides achieved complete bacterial killing in 20 min or less against Gram‐negative bacteria. A linear time‐dependent membrane permeabilization was observed for the tested peptides at 12.5 µg/ml. In a medium containing Mg²⁺ and Ca²⁺, the peptide combination with EDTA restores the antimicrobial activity particularly for AMP2041. Moreover, in combination with anti‐infective agents (quinolones or aminoglycosides) known to bind divalent cation, AMP126 and AMP2041 showed additive activity in comparison with colistin. Our results suggest the following: (i) there is excellent activity against Gram‐negative bacteria, (ii) there is low cytolytic activity, (iii) the presence of a chelating agent restores the antimicrobial activity in a medium containing Mg²⁺ and Ca²⁺, and (iv) the MBC value of the combination AMPs–conventional antibiotics was lower than the MBC of single agents alone. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Preparation and characterization of oxochromium(IV) and nickel(II) complexes with 5,14-dihydro-7,16-diethyl-(E)- or -(Z)-dipyrido[b,i][1,4,8,11]tetraazacyclotetradecine

The reaction of 5,14-dihydro-7,16-diethyl-(E) or -(Z)-dipyrido[b,i][1,4,8,11]tetraazacyclotetradecine with chromium hexacarbonyl produced the corresponding oxochromium(IV) complexes. These compounds had intense bands in the infrared region at 985 cm⁻¹, which are attributed to the CrO stretching modes. The two complexes gave mass spectra with prominent parent and parent-O peaks. On the other hand the mass spectra for the nickel(II) complexes showed parent and parent-CH₃ peaks. The absorption bands appearing in the energy range greater than 19 000 cm⁻¹ were attributable to the π→π* and CT transitions. Consistent with their diamagnetism, the oxochromium complexes gave well-resolved proton NMR and carbon-13 NMR spectra. The magnitude of downfield shifts for the oxochromium(IV) complex is much larger than that observed for the corresponding nickel(II) complex. This is due to the fact that the positive charge provided by chromium(IV) is greater in magnitude than that by nickel(II).     

Synthesis,characterization and antimicrobial activities of novel silver(I) complexes with coumarin substituted N-heterocyclic carbene ligands

Eight new coumarin substituted silver(I) N-heterocyclic carbene (NHC) complexes were synthesized by the interaction of the corresponding imidazolium or benzimidazolium chlorides and Ag₂O in dichloromethane at room temperature. Structures of these complexes were established on the basis of elemental analysis, ¹H NMR, ¹³C NMR, IR and mass spectroscopic techniques. The antimicrobial activities of carbene precursors and silver NHC complexes were tested against standard strains: Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungi Candida albicans and Candida tropicalis. Results showed that all the compounds inhibited the growth of the all bacteria and fungi strains and some complexes performed good activities against different microorganisms. Among all the compounds, the most lipophilic complex bis[1-(4-methylene-6,8-dimethyl-2H-chromen-2-one)-3-(naphthalene-2-ylmethyl)benzimidazol-2-ylidene]silver(I) dichloro argentate (5e) was found out as the most active one.     

Metal-based biologically active azoles and β-lactams derived from sulfa drugs

Metal complexes of Schiff bases derived from sulfamethoxazole (SMZ) and sulfathiazole (STZ), converted to their β-lactam derivatives have been synthesized and experimentally characterized by elemental analysis, spectral (IR, ¹H NMR, ¹³C NMR, and EI-mass), molar conductance measurements and thermal analysis techniques. The structural and electronic properties of the studied molecules were investigated theoretically by performing density functional theory (DFT) to access reliable results to the experimental values. The spectral and thermal analysis reveals that the Schiff bases act as bidentate ligands via the coordination of azomethine nitrogen to metal ions as well as the proton displacement from the phenolic group through the metal ions; therefore, Cu complexes can attain the square planner arrangement and Zn complexes have a distorted tetrahedral structure. The thermogravimetric (TG/DTG) analyses confirm high stability for all complexes followed by thermal decomposition in different steps. In addition, the antibacterial activities of synthesized compounds have been screened in vitro against various pathogenic bacterial species. Inspection of the results revealed that all newly synthesized complexes individually exhibit varying degrees of inhibitory effects on the growth of the tested bacterial species, therefore, they may be considered as drug candidates for bacterial pathogens. The free Schiff base ligands (1–2) exhibited a broad spectrum antibacterial activity against Gram negative Escherichia coli, Pseudomonas aeruginosa, and Proteus spp., and Gram positive Staphylococcus aureus bacterial strains. The results also indicated that the β-lactam derivatives (3–4) have high antibacterial activities on Gram positive bacteria as well as the metal complexes (5–8), particularly Zn complexes, have a significant activity against all Gram negative bacterial strains. It has been shown that the metal complexes have significantly higher activity than corresponding ligands due to chelation process which reduces the polarity of metal ion by coordinating with ligands.     

Palladium(II) complexes of quinolinylaminophosphonates: synthesis, structural characterization, antitumor and antimicrobial activity

Three types of palladium(II) halide complexes of quinolinylaminophosphonates have been synthesized and studied. Diethyl and dibutyl [α-anilino-(quinolin-2-ylmethyl)]phosphonates (L1, L2) act as N,N-chelate ligands through the quinoline and aniline nitrogens giving complexes cis-[Pd(L1/L2)X₂] (X═Cl, Br) (1-4). Their 3-substituted analogues [α-anilino-(quinolin-3-ylmethyl)]phosphonates (L3, L4) form dihalidopalladium complexes trans-[Pd(L3/L4)₂X₂] (5-8), with trans N-bonded ligand molecules only through the quinoline nitrogen. Dialkyl [α-(quinolin-3-ylamino)-N-benzyl]phosphonates (L5, L6) give tetrahalidodipalladium complexes [Pd₂(L5/L6)₃X₄] (9-12), containing one bridging and two terminal ligand molecules. The bridging molecule is bonded to the both palladium atoms, one through the quinoline and the other through the aminoquinoline nitrogen, whereas terminal ligand molecules are coordinated each only to one palladium via the quinoline nitrogen. Each palladium ion is also bonded to two halide ions in a trans square-planar fashion. The new complexes were identified and characterized by elemental analyses and by IR, UV-visible, ¹H, ¹³C and ³¹P nuclear magnetic resonance and ESI-mass spectroscopic studies. The crystal structures of complexes 1-4 and 6 were determined by X-ray structure analysis. The antitumor activity of complexes in vitro was investigated on several human tumor cell lines and the highest activity with cell growth inhibitory effects in the low micromolar range was observed for dipalladium complexes 11 and 12 derived from dibutyl ester L6. The antimicrobial properties in vitro of ligands and their complexes were studied using a wide spectrum of bacterial and fungal strains. No specific activity was noted. Only ligands L3 and L4 and tetrahalidodipalladium complexes 9 and 11 show poor activities against some Gram positive bacteria.     

Synthesis, crystal structures, cytotoxicity and qualitative structure-activity relationship (QSAR) of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes, (n)Bu2Sn(L)2

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes has been synthesized and characterized by ¹H-, ¹³C-, ¹¹⁹Sn NMR, ESI-MS (electrospray ionization mass spectrometry), IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The structures of four di-n-butyltin(IV) complexes, viz., ⁿBu₂Sn(L³)₂ (3), ⁿBu₂Sn(L⁴)₂ (4), ⁿBu₂Sn(L⁵)₂ (5) and ⁿBu₂Sn(L⁷)₂ · 0.5C₆H₆ (7) (LH = 5-[(E)-2-(aryl)-1-diazenyl)quinolin-8-ol) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by ¹¹⁹Sn and ¹³C NMR spectroscopic results. The in vitro cytotoxicity of di-n-butyltin(IV) complexes (3-8) is reported against seven well characterized human tumour cell lines. The basicity of the two quinolinolato donor N and O atoms of the ligands are discussed in relation to the cytotoxicity data.