Aqua substitution from mononuclear Pt(II) complexes with 2-(pyrazol-1-ylmethyl)quinoline non-leaving ligands

The rates of aqua substitution from [Pt{2-(pyrazol-1-ylmethyl)quinoline}(H₂O)₂](ClO₄)₂, [Pt(H₂Qn)], [Pt{2-(3,5-dimethylpyrazol-1-ylmethyl)quinoline}(H₂O)₂](ClO₄)₂, [Pt(dCH₃Qn)], [Pt{2-[(3,5-bis(trifluoromethyl)pyrazol-1-ylmethyl]quinoline}(H₂O)₂](ClO₄)₂, [Pt(dCF₃Qn)], and [Pt{2-[(3,5-bis(trifluoromethyl)pyrazol-1-ylmethyl]pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCF₃Py)], with three sulfur donor nucleophiles were studied. The reactions were followed under pseudo-first-order conditions as a function of nucleophile concentration and temperature using a stopped-flow analyzer and UV/visible spectrophotometry. The substitution reactions proceeded sequentially. The second-order rate constants for substituting the aqua ligands in the first substitution step increased in the order Pt(dCH₃Qn) < Pt(dCF₃Qn) < Pt(H₂Qn) < Pt(dCF₃Py), while that of the second substitution step was Pt(dCH₃Qn) < Pt(dCF₃Qn) < Pt(dCF₃Py) < Pt(H₂Qn). The reactivity trends confirm that the quinoline substructure in the (pyrazolylmethyl)quinoline ligands acts as an apparent donor of electron density toward the metal center rather than being a π-acceptor. Measured pK_a values from spectrophotometric acid–base titrations were Pt(H₂Qn) (pK_a1 = 4.56; pK_a2 = 6.32), Pt(dCH₃Qn) (pK_a1 = 4.88; pK_a2 = 6.31), Pt(dCF₃Qn) (pK_a1 = 4.07; pK_a2 = 6.35), and Pt(dCF₃Py) (pK_a1 = 4.76; pK_a2 = 6.27). The activation parameters from the temperature dependence of the second-order rate constants support an associative mechanism of substitution.     

Characterization of new Pt(IV)–thiazole complexes: Analytical,spectral, molecular modeling and molecular docking studies and applications in two opposing pathways

New thiazole derivatives were synthesized and fully characterized, then coordinated with PtCl₄ salt. Also, the newly synthesized Pt(IV) complexes were investigated analytically (elemental and thermogravimetric analyses), spectrally (infrared, UV–visible, mass, ¹H NMR, ¹³C NMR, X‐ray diffraction) as well as theoretically (kinetics, modeling and docking). The data extracted led to the establishment of the best chemical and structural forms. Octahedral geometry was the only formula proposed for all complexes, which is favorable for d⁶ systems. The molecular ion peaks from mass spectral analysis coincide with all analytical data, confirming the molecular formula proposed. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) allowed discrimination of features between crystalline particles and other amorphous morphology. By applying Gaussian09 as well as HyperChem 8.2 programs, the best structural forms were obtained, as well as computed significant parameters. Computed parameters such as softness, hardness, surface area and reactivity led us towards application in two opposing pathways: tumor inhibition and oxidation activation. The catalytic oxidation for CO was conducted over PtO₂, which was yielded from calcination of the most reactive complex. The success of catalytic role for synthesized PtO₂ was due to its particulate size and surface morphology, which were estimated from XRD patterns and SEM images, respectively. The antitumor activity was tested versus HCT‐116 and HepG‐2 cell lines. Mild toxicity was recorded for two of the derivatives and their corresponding complexes. This degree of toxicity is more favorable in most cases, due to exclusion of serious side effects, which is coherently attached with known antitumor drugs.     

Synthesis and characterization of binuclear manganese(IV,IV) and mononuclear cobalt(II) complexes based on 2-(2-hydroxyphenyl)-1H-benzimidazole

The bidentate benzimidazolic hpbm (1), [2-(2-hydroxyphenyl)-1H-benzimidazole], was obtained under mild conditions, and its corresponding metal complexes, di-µ-oxo dimanganese(IV,IV) [Mn₂O₂(hpbm)₄ · 2Py · 5H₂O] (2), and mononuclear complex [Co(hpbm)₂] (3), were prepared and characterized. The crystal structures of 2 and 3 have been established by X-ray diffraction. Complex 2 consists of two six-coordinate manganese(IV) coordinated to two hpbm ligands and bridged by two O^2? with a Mn–Mn distance of 2.777 Å. For 3, a Co(II) is coordinated to two deprotonated hpbm in a nearly tetrahedral environment. Hydrogen bonds play pivotal roles in constructing the dimensional structures of both the compounds.     

Studies on monocyclopentadienyl titanium(IV) dithiocarbamato complexes

Titanium(IV) dithiocarbamato complexes of the typesCpTi(S₂CNHR)Cl₂ andCpTi(S₂CNHR)₂Cl, whereR=C₈H₅N₂S, C₉H₅N₂SCl₂ and C₉H₇N₂S, have been prepared by the reaction of monocyclopentadienyl titanium(IV) trichloride with the potassium salt of the appropriate dithiocarbamic acid in anhydrous dichloromethane. Conductance and infrared studies indicate that these complexes are non-electrolytes in which all dithiocarbamate ligands are bidentate. Therefore, 5 and 6 coordinate structures can be assigned toCpTi(S₂CNHR)Cl₂ andCpTi(S₂CNHR)₂Cl complexes, respectively.¹H-NMR spectra indicate that there is rapid rotation of the cyclopentadienyl ring about the metal ring axis.

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Untersuchungen von Monocyclopentadienyl-titan(IV)-dithiocarbamat-Komplexen

Zusammenfassung Es wurden Titan(IV)-dithiocarbamat-Komplexe vom TypCpTi(S₂CNHR)Cl₂ undCpTi(S₂CNHR)₂Cl mitR=C₈H₅N₂S, C₉H₅N₂SCl₂ und C₉H₇N₂S mittels der Reaktion von Monocyclopentadienyltitan(IV)trichlorid mit dem Kaliumsalz der entsprechenden Dithiocarbaminsäure in wasserfreiem Dichlormethan dargestellt. Leitfähigkeitsmessungen und IR-Untersuchungen zeigen, daß diese Komplexe Nichtelektrolyte sind, bei denen alle Dithiocarbamat-Liganden zweizähnig sind. Demnach können 5-, bzw. 6-koordinierte Strukturen für die Komplexe des TypsCpTi(S₂CNHR)Cl₂, bzw.CpTi(S₂CNHR)₂Cl angenommen werden. Die¹H-NMR Spektren zeigen eine rasche Rotation des Cyclopentadienylrings um die Metall-Ring Achse an.

     

Synthesis,characterization, reactivity,and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂]?·?nH₂O (where A?=?py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN?=?bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.     

The in vitro antifungal activity of some dithiocarbamate organotin(IV) compounds on Candida albicans— a model for biological interaction of organotin complexes

The in vitro antifungal activity of the dithiocarbamate organotin complexes [Sn{S₂CN(CH₂)₄}₂Cl₂] ( 1 ), [Sn{S₂CN(CH₂)₄}₂Ph₂] ( 2 ), [Sn{S₂CN(CH₂)₄}Ph₃] ( 3 ), [Sn{S₂CN(CH₂)₄}₂n‐Bu₂] ( 4 ), [Sn{S₂CN(CH₂)₄}Cy₃] {Cy = cyclohexyl} ( 5 ), [Sn{S₂CN(C₂H₅)₂}₂Cl₂] ( 6 ), [Sn{S₂CN(C₂H₅)₂}₂Ph₂] ( 7 ), [Sn{S₂CN(C₂H₅)₂}Ph₃] ( 8 ), [Sn{S₂CN(C₂H₅)₂}₃Ph] ( 9 ) and [Sn{S₂CN(C₂H₅)₂}Cy₃] ( 10 ) has been screened against Candida albicans (ATCC 18804), Candida tropicalis (ATCC 750) and resistant Candida albicans collected from HIV‐positive Brazilian patients with oral candidiasis. All compounds exhibited antifungal activities and complexes 3 and 8 displayed the best results. We have investigated the effect of compounds 1–10 on the cellular activity of the yeast cultures. Changes in mitochondrial function have not been detected. However, all drugs reduced ergosterol biosynthesis. Preliminary studies on DNA integrity indicated that the compounds do not cause gross damage to yeast DNA. The data suggest that these compounds share some mechanisms of action on cell membranes similar to that of polyene but not with azole drugs, normally used in Candida infections. Copyright © 2008 John Wiley & Sons, Ltd.     

Accurate determination of the CO coverage at saturation on a cyanide-modified Pt(1 1 1) electrode in cyanide-free 0.5 M H2SO4

We have used the CO charge-displacement method, in combination with a thermodynamic cycle, to obtain the double-layer correction necessary to determine accurately, using the charge in the corresponding CO-stripping voltammograms, the maximum amount of CO that can adsorb on a cyanide-modified Pt(1 1 1) electrode. The resulting CO coverage at saturation is θ_CO=0.25, and corresponds to a mixed CN–CO adlayer where some Pt atoms are still free and consequently can adsorb hydrogen. The hydrogen adsorption charge for the mixed adlayer, obtained from the corresponding cyclic voltammogram, agrees very well with that estimated from the CO and CN coverages, assuming that one hydrogen atom adsorbs on every free Pt atom. Taking into account these data, we propose a structural model for the mixed CN–CO adlayer on Pt(1 1 1).     

Molecular and Supramolecular Structures of 1‐Phenyl‐4‐phenylacetyl‐2‐thiosemicarbazide (H2L) and its Complexes with Diphenyllead(IV) Chloride and Acetate

Reaction of 1‐phenyl‐4‐phenylacetyl‐2‐thiosemicarbazide (H₂L) with diphenyllead(IV) dichloride and acetate afforded the complexes [PbPh₂Cl₂(H₂L)₂] and [PbPh₂L]. The ligand and the complexes were characterized by elemental analyses, ¹H and ¹³C NMR spectroscopy and X‐ray crystallography. In the asymmetric unit of crystals of the ligand there are four independent molecules of H₂L and four molecules of water, which associate in the lattice as two independent sheets. The complex [PbPh₂Cl₂(H₂L)₂]·4MeOH has slightly distorted all‐trans octahedral geometry around the lead atom, and the fact that the ligand is S‐bound rather than O‐bound suggests that PbPh₂Cl₂ behaves as a “soft” Lewis acid. Hydrogen bonds involving NH groups, Cl atoms and MeOH molecules form a three‐dimensional supramolecular structure. In [PbPh₂L]·Me₂CO, the L^2? anion bridges between two metal centres, binding to one strongly via the N and S atoms and weakly via the O atom, and to the other via the O atom, thus creating polymeric chains along the b axis. The double deprotonation and metallation of H₂L induce significant changes in its configuration and lengthen the C‐S and C‐O bonds, suggesting an evolution of the dianion towards a thiol‐enol form.     

Synthesis and Biological Studies on (KLAKLAK)2-NH2 Analog Containing Unnatural Amino Acid β-Ala and Conjugates with Second Pharmacophore

(1) Background: Peptides are good candidates for anticancer drugs due to their natural existence in the body and lack of secondary effects. (KLAKLAK)₂ is an antimicrobial peptide that also shows good anticancer properties. (2) Methods: The Solid Phase Peptide Synthesis (Fmoc-strategy) was used for the synthesis of target molecules, analogs of (KLAKLAK)₂-NH₂. The purity of all compounds was monitored by HPLC, and their structures were proven using mass spectrometry. Cytotoxicity and antiproliferative effects were studied using 3T3 NRU and MTT tests, respectively. For determination of antimicrobial activity, the disc-diffusion method was used. Hydrolytic stability at three pH values, which mimic the physiological pH in the body, was investigated by means of the HPLC technique. (3) Results: A good selective index against MCF-7 tumor cell lines, combined with good cytotoxicity and antiproliferative properties, was revealed for conjugates NphtG-(KLAKLAK)₂-NH₂ and Caf-(KLAKLAK)₂-NH₂. The same compounds showed very good antifungal properties and complete hydrolytic stability for 72 h. The compound Caf-(KLβ-AKLβ-AK)₂-NH₂ containing β-Ala in its structures exhibited good antimicrobial activity against Escherichia coli K12 407 and Bacillus subtilis 3562, in combination with very good antiproliferative and cytotoxic properties, as well as hydrolytic stability. (4) Conclusions: The obtained results reveal that all synthesized conjugates could be useful for medical practice as anticancer or antimicrobial agents.     

In Vitro Evaluation of Antiproliferative Properties of Novel Organotin(IV) Carboxylate Compounds with Propanoic Acid Derivatives on a Panel of Human Cancer Cell Lines

The synthesis of novel triphenyltin(IV) compounds, Ph₃SnLn (n = 1–3), with oxaprozin (3-(4,5-diphenyloxazol-2-yl)propanoic acid), HL1, and the new propanoic acid derivatives 3-(4,5-bis(4-methoxylphenyl)oxazol-2-yl)propanoic acid, HL2, and 3-(2,5-dioxo-4,4-diphenylimidazolidin-1-yl)propanoic acid, HL3, has been performed. The ligands represent commercial drugs or their derivatives and the tin complexes have been characterized by standard analytical methods. The in vitro antiproliferative activity of both ligands and organotin(IV) compounds has been evaluated on the following tumour cell lines: human prostate cancer (PC-3), human colorectal adenocarcinoma (HT-29), breast cancer (MCF-7), and hepatocellular cancer (HepG2), as well as on normal mouse embryonic fibroblast cells (NIH3T3) with the aid of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-12 diphenyltetrazolium bromide) and CV (crystal violet) assays. Contrary to the inactive ligand precursors, all organotin(IV) carboxylates showed very good activity with IC₅₀ values ranging from 0.100 to 0.758 µM. According to the CV assay (IC₅₀ = 0.218 ± 0.025 µM), complex Ph₃SnL1 demonstrated the highest cytotoxicity against the caspase 3 deficient MCF-7 cell line. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated a two-fold lower concentration of tin in MCF-7 cells in comparison to platinum. To investigate the mechanism of action of the compound Ph₃SnL1 on MCF-7 cells, morphological, autophagy and cell cycle analysis, as well as the activation of caspase and ROS/RNS and NO production, has been performed. Results suggest that Ph₃SnL1 induces caspase-independent apoptosis in MCF-7 cells.     

1-Ethylthio-2-[2-thienyltelluro]ethane (L) a new (Te, S) ligand: Synthesis and complexation with Ag(I), Cu(I), Pd(II) and Pt(II) – Single crystal structures of [PdCl2(L)] and bis(thienyl) tellurium(IV) chloride

Lithium 2-thienyltellurolate, generated from 2-thienyl lithium, reacts at −78 °C in THF with chloroethyl ethyl sulfide to give a (Te, S) ligand 1-ethylthio-2-[2-thienyltelluro]ethane (L) as a red oil. The complexes [PdCl₂(L)] (1), [PtCl₂(L)] (2), [Ag(L)₂][ClO₄] (3) and [CuBr(L)]₂ (4) were synthesized. The complex [HgCl₂(L)] on crystallization decomposed giving Th₂TeCl₂ (5) [where Th = 2-thienyl], which was characterized by X-ray diffraction on its single crystals. The ligand L and complexes 1–4 exhibit proton and carbon-13 NMR spectra, which are characteristic. The coordination through Te in 1–4 is indicated by downfield coordination shifts in the position of the TeCH₂ signal of L. Complex 1 was characterized by X-ray diffraction on its single crystals. The geometry around Pd is square planar. The Pd–Te, Pd–S and Pd–Cl bond lengths are 2.5040(4), 2.273(1) and 2.322(1)/2.380(1) Å, respectively. There are intermolecular interactions between Te (coordinated to Pd) and Cl, and sulfur and Cl. The Te–Cl and S–Cl distances, 3.401 and 3.488 Å, respectively, are shorter than the sum of the van der Waal’s radii (3.81 and 3.55 Å, respectively). The Pd–Pd distance between the two molecules is 3.4156(6) Å, greater than the sum of van der Waal’s radii (3.26 Å). The structure of 5 is typical of that of a tellurium(IV) compound (saw-horse type). The two Te–Cl bond lengths are identical, 2.480(1) Å. The geometry around Te in 5 can be best described as pseudo tetrahedral (trigonal bipyramidal with a lone pair on one corner of the triangle).     

Chemistry of oxovanadium(IV) bound to tetradentate ONNO donors: Influence of axial coordination on the V-O(1)bond

Chelating behaviour of some tetradenate ONNO donors derived fromq - aminobenzoylhydrazide and some diketones toward oxo-vanadium(IV) ion is reported. The donors react with oxometal cation depending on the pH of the reaction medium. The product containing the neutral keto and the binegative enol form of the donors have the formulae [VO(H₂L)(SO₄)] (at pH 3.0)(┘1) and [VO(L)(H₂O)] (at pH 6.0)(┘2) respectively [H₂L = (2-NH₂)C₆H₄CONH: C(R) (CH₂)_mC(R): NNH CO C₆H₄(2−NH₂); H₂L = H₂DA(R= CH₃,m = 0), H₂BA(R = C₆H₅,m = 0), H₂AA(R = CH₃,m = 2)]. Both (┘1) and (┘2) react with a neutral monodentate donor B(B = pyridine, aniline etc.) yielding mixed-ligand complexes [VO(L)(B)]. Influence of the axial coordination on the V-O₍₁₎ bond is discussed and a monomeric distorted octahedral donor environment for the oxovanadium(IV) ion has been suggested     

New insights on the Lewis acidity of diorganolead(IV) compounds: Diphenyllead(IV) complexes with N,O,S-chelating ligands

The reactions of PbPh₂(OAc)₂ with alkylglyoxylate thiosemicarbazones (HRGTSC, R = Et, Bu) afforded complexes of the type [PbPh₂(GTSC)] · H₂O, [PbPh₂(RGTSC)₂] and [PbPh₂Cl(BuGTSC)]. The structures of HRGTSC (R = Me, Et, Bu), [PbPh₂(OAc)(RGTSC)](R = Me, Et, Bu), [PbPh₂Cl(BuGTSC)] and [PbPh₂(GTSC)] · H₂O have been studied by X-ray diffraction. [PbPh₂(OAc)(RGTSC)] and [PbPh₂(GTSC)] · H₂O have [PbC₂NO₃S] kernels and the coordination sphere of the metal is pentagonal bipyramidal. [PbPh₂Cl(BuGTSC)] has a [PbC₂NOSCl] kernel and the coordination geometry around lead is pentagonal bipyramidal with one vacant site. Analysis of the bond distances in [PbPh₂(GTSC)] · H₂O suggests a significant affinity between diphenyllead(IV) and carboxylate donor groups, supporting a borderline acidic character for this organometallic cation. ¹H and ¹³C NMR spectra in DMSO-d₆ suggest the partial dissociation of the acetate in [PbPh₂(OAc)(RGTSC)] solutions and indicate some differences in the coordination mode of the two RGTSC⁻ ligands in [PbPh₂(RGTSC)₂] complexes.     

Magneto-structural study on a series of rhenium(IV) complexes containing biimH2, pyim and bipy ligands

Three rhenium(IV) mononuclear compounds of formulae [ReCl₄(biimH₂)] · 2DMF (1), [ReCl₄(pyim)] · DMF (2) and [ReCl₄(bipy)] (3) (biimH₂ = 2,2′-biimidazole, pyim = 2-(2′-pyridyl)imidazole, bipy = 2,2′-bipyridine and DMF = N,N-dimethylformamide) have been prepared and characterized. The crystal structure of 2 was determined by single crystal X-ray diffraction. Compound 2 crystallizes in the monoclinic system with P2₁/c as space group. The rhenium atom is six-coordinated by four Cl atoms and two nitrogen atoms from a bidentate pyim ligand [average values of Re–Cl and Re–N bonds lengths being 2.330(2) and 2.117(4) Å, respectively]. The magnetic properties were investigated from susceptibility measurements performed on polycrystalline samples of 1–3 in the temperature range 1.9–300 K. The magnetic behaviour found is typical of antiferromagnetically coupled systems, and they exhibit susceptibility maxima at 2.8 (1 and 2) and 5.6 K (3). Short Re^IV–Cl?Cl–Re^IV contacts through space account for the antiferromagnetic behaviour observed.     

Synthesis, structural and spectral studies of Cu(II) and V(IV) complexes of a novel Schiff base derived from pyridoxal. Antimicrobial activity

A novel Schiff base, N-(4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one)pyridoxaldimine (HL·HCl), was prepared and structurally characterized on the basis of elemental analyses, ¹H and ¹³C NMR, and IR spectral data. The synthesis and characterization of several Cu(II) (1-6) and V(IV) (7) complexes with N-(4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one)pyridoxaldimine are reported. The composition and structures of the copper(II) and vanadium(IV) complexes were proposed based on elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic and EPR spectroscopy. In addition, the structures of the ligand and the complex [CuL(H₂O)₂]NO₃·2.25H₂O (1) have been determined by single-crystal X-ray diffraction, showing that the Cu(II) center has a distorted square-pyramidal geometry. The ligand and the complexes were also tested for their in vitro antibacterial activity.     

In vitro binding studies of organotin(IV) complexes of 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol with CT-DNA and nucleotides (5′-GMP and 5′-TMP): Effect of the ancillary ligand on the binding propensity

The chiral benzimidazole ligand, 1,2-Bis(1H-benzimidazol-2-yl)ethane-1,2-diol, L, exhibiting coordination mode with an oxygen atom of alcohol group directed towards the metal ion and another -OH group with different molecular axis directed away from the metal center was utilized as a building block for organotin complexes [C₁₈H₁₉N₄O₂SnCl], [C₂₈H₂₃N₄O₂SnCl] and [C₅₂H₄₂N₄O₂Sn₂] (1-3). Complexes 1 and 3 exhibit a pentacoordinate geometry while the complex 2 reveals hexacoordinated environment around the Sn(IV) metal ions as evidenced by ¹¹⁹Sn NMR studies. The DNA binding ability of benzimidazole ligand and their organotin(IV) complexes 1-3 were examined by employing different biophysical methods. The absorption titration of the complexes with CT-DNA reveal significant hyperchromic effect together with strong bathochromic shift of 4-5 nm which infer substantial binding of the complexes with CT-DNA. The intrinsic binding constant K_b values of the complexes 1-3 were found to be 2.16 ± 0.04 × 10⁴, 3.47 ± 0.04 × 10⁴ and 4.60 ± 0.04 × 10³ M⁻¹, respectively, suggesting pronounced binding of complex 2 with DNA double helix. The mechanism of binding of the complexes was further ascertained by the interaction studies of these complexes with nucleotides (5′-GMP and 5′-TMP) using absorption spectroscopy suggesting a clear preference for 5′-GMP binding which was further authenticated by NMR (¹H and ³¹P NMR) studies.     

Diphenyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and multinuclear NMR, Sn Mössbauer, electrospray ionization MS, X-ray characterization and assessment of in vitro cytotoxicity

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}diphenyltin(IV) complexes have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The structures of a ligand L⁶H (i.e., 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]quinolin-8-ol) and three diphenyltin(IV) complexes, viz., Ph₂Sn(L¹)₂ · (CH₃)₂CO (1), Ph₂Sn(L⁴)₂ (4) and Ph₂Sn(L⁵)₂ (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = phenyl - (L¹H); 4′-methylphenyl - (L⁴H) and 4′-bromophenyl - (L⁵H)) 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 NMR spectroscopic results. The in vitro cytotoxicity of 1 is reported and compared with Ph₂Sn(Ox)₂ (Ox = deprotonated quinolin-8-ol) against seven well characterized human tumor cell lines.