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Quite recently we discovered that copper(II) complexes with isomeric morpholine-thiosemicarbazone hybrid ligands show good cytotoxicity in cancer cells and that the molecular target responsible for this activity might be tubulin. In order to obtain better lead drug candidates, we opted to exploit the power of coordination chemistry to (i) assemble structures with globular shape to better fit the colchicine pocket and (ii) vary the metal ion. We report the synthesis and full characterization of bis-ligand cobalt(III) and iron(III) complexes with 6-morpholinomethyl-2-formylpyridine 4N-(4-hydroxy-3,5-dimethylphenyl)-3-thiosemicarbazone (HL1), 6-morpholinomethyl-2-acetylpyridine 4N-(4-hydroxy-3,5-dimethylphenyl)-3-thiosemicarbazone (HL2), and 6-morpholinomethyl-2-formylpyridine 4N-phenyl-3-thiosemicarbazone (HL3), and mono-ligand nickel(II), zinc(II) and palladium(II) complexes with HL1, namely [CoIII(HL1)(L1)](NO3)2 (1), [CoIII(HL2)(L2)](NO3)2 (2), [CoIII(HL3)(L3)](NO3)2 (3), [FeIII(L2)2]NO3 (4), [FeIII(HL3)(L3)](NO3)2 (5), [NiII(L1)]Cl (6), [Zn(L1)Cl] (7) and [PdII(HL1)Cl]Cl (8). We discuss the effect of the metal identity and metal complex stoichiometry on in vitro cytotoxicity and antitubulin activity. The high antiproliferative activity of complex 4 correlated well with inhibition of tubulin polymerization. Insights into the mechanism of antiproliferative activity were supported by experimental results and molecular docking calculations. [ABSTRACT FROM AUTHOR]

A series of latonduine derivatives, namely 11-nitro-indolo[2,3-d]benzazepine-7-(1-amino-hydantoin) (B), triazole-fused indolo[2,3-d]benzazepine-based Schiff bases HL1 and HL2 and metal complexes [M(p-cymene)(HL1)Cl]Cl, where M = Ru (1), Os (2), and [Cu(HL2)Cl2] (3) were synthesized and characterized by spectroscopic techniques (UV–vis, 1H, 13C, 15N–1H HSQC NMR) and ESI mass spectrometry. The molecular structures of B and HL1 were confirmed by single-crystal X-ray diffraction, while that of 3 by electron diffraction of nanometer size crystalline sample. Molecular docking calculations of species B in the binding pocket of PIM-1 enzyme revealed that the 1-amino-hydantoin moiety is not involved in any hydrogen-bonding interactions, even though a good accommodation of the host molecule in the ATP binding pocket of the enzyme was found. The antiproliferative activity of organic compounds B, HL1 and HL2, as well as complexes 1–3 was investigated in lung adenocarcinoma A549, colon adenocarcinoma LS-174 and triple-negative breast adenocarcinoma MDA-MB-231 cells and normal human lung fibroblast cells MRC-5 by MTT assays; then, the results are discussed. [ABSTRACT FROM AUTHOR]

The proton dissociation processes of two tridentate salicylidene aminoguanidine Schiff bases (SISC, Pro-SISC-Me), the solution stability and electrochemical properties of their Cu(II), Fe(II) and Fe(III) complexes were characterized using pH-potentiometry, cyclic voltammetry and UV-visible, 1H NMR and electron paramagnetic resonance spectroscopic methods. The structure of the proline derivative (Pro-SISC-Me) was determined by X-ray crystallography. The conjugation of L-proline to the simplest salicylidene aminoguanidine Schiff base (SISC) increased the water solubility due to its zwitterionic structure in a wide pH range. The formation of mono complexes with both ligands was found in the case of Cu(II) and Fe(II), while bis complexes were also formed with Fe(III). In the complexes these tridentate ligands coordinate via the phenolato O, azomethine N and the amidine N, except the complex [Fe(III)L2]+ of Pro-SISC-Me in which the (O,N) donor atoms of the proline moiety are coordinated beside the phenolato O, confirmed by single crystal X-ray crystallographic analysis. This binding mode yielded a stronger Fe(III) preference for Pro-SISC-Me over Fe(II) in comparison to SISC. This finding is also reflected in the lower redox potential value of the iron-Pro-SISC-Me complexes. The ligands alone were not cytotoxic against human colon cancer cell lines, while complexation of SISC with Cu(II) resulted in moderate activity, unlike the case of its more hydrophilic counterpart. [ABSTRACT FROM AUTHOR]

A series of five iron(III) complexes, namely [Fe(HL1)Cl2] (1), [Fe(HL2)Cl2]·1.6H2O (2·1.6H2O), [Fe(HL3)(MeOH)Cl2]·0.5H2O (3·0.5H2O), [Fe(HL4)(MeOH)Cl2]·0.5H2O (4·0.5H2O) and [Fe(HL4)(DMF)Cl2]·0.5Et2O·H2O (4′·0.5Et2O·H2O), where H2L1 = l-proline-salicylaldehyde–thiosemicarbazone (l-Pro-STSC), H2L2 = pyrrolidine-substituted l-Pro-STSC, H2L3 = phenyl-substituted l-Pro-STSC, and H2L4 = naphthyl-substituted l-Pro-STSC, have been synthesized. The two ligand precursors (H2L3 and H2L4) and iron complexes were characterized by elemental analysis, spectroscopic methods (UV/Vis, IR, and NMR), ESI mass spectrometry, cyclic voltammetry, and single-crystal X-ray crystallography (1–3 and 4′). Magnetic properties of the five-coordinate complex 2 and six-coordinate complex 4 have also been investigated. The antiproliferative activity of the organic hybrids and their iron(III) complexes have been studied in vitro in five human cell lines and one murine cancer cell line, namely HeLa (cervical cancer), FemX (melanoma), A549 (alveolar basal adenocarcinoma), LS-174 (colon cancer), MDA-MB-453 (breast cancer) and MS1 (transformed murine endothelial), as well as in human noncancerous fetal lung fibroblast cell line (MRC-5). According to the structure–activity relationship, introduction of aromatic groups such as phenyl or naphthyl enhances the cytotoxic potency of the hybrids in the following order H2L1 < H2L2 < H2L3 < H2L4. Coordination of the hybrids to iron(III) improves their antiproliferative activity in the majority of investigated cell lines with exception of H2L3 in LS-174, H2L4 in MS1, and both H2L3 and H2L4 in FemX cell lines, where an opposite effect was observed. [ABSTRACT FROM AUTHOR]

Two water-soluble thiosemicarbazone-proline (H2L1) and thiosemicarbazone-homoproline hybrids (H2L2) were synthesised. By reaction of H2L1 with NiCl2·6H2O, PdCl2 and CuCl2·2H2O in ethanol, the series of square-planar complexes [Ni(H2L1)Cl]Cl·1.3H2O (1·1.3H2O), [Pd(H2L1)Cl]Cl·H2O (2·H2O) and [Cu(H2L1)Cl]Cl·0.7H2O (3·0.7H2O) was prepared, and starting from H2L2 and CuCl2·2H2O in methanol, the complex [Cu(H2L2)Cl2]·H2O (4·H2O) was obtained. The compounds have been characterised by elemental analysis, spectroscopic methods (IR, UV-vis and NMR spectroscopy), ESI mass spectrometry and single crystal X-ray crystallography (H2L1, 1, 2 and 4). As a solid, 1 is diamagnetic, while it is paramagnetic in methanolic solution. The effective magnetic moment of 3.26 B.M. at room temperature indicates the change in coordination geometry from square-planar to octahedral upon dissolution. The in vitro anticancer potency of ligand precursors H2L1 and H2L2 and metal complexes 1–4 was studied in three human cancer cell lines (A549, CH1 and SW480) and in noncancerous murine embryonal fibroblasts (NIH/3T3), and the mechanism of cell death was also assayed by flow cytometry. Clear-cut structure–activity relationships have been established. The metal ions exert marked effects in a divergent manner: copper(ii) increases, whereas nickel(ii) and palladium(ii) decrease the cytotoxicity of the hybrids. The antiproliferative activity of H2L1 and metal complexes 1–3 decreases in all three tumour cell lines in the following rank order: 3 ＞ H2L1 ＞ 1 ＞ 2. The role of square-planar geometry in the underlying mechanism of cytotoxicity of the metal complexes studied seems to be negligible, while structural modifications at the terminal amino group of thiosemicarbazide and proline moieties are significant for enhancing the antiproliferative activity of both hybrids and copper(ii) complexes. [ABSTRACT FROM AUTHOR]

Two water-soluble thiosemicarbazone-proline (H2L1) and thiosemicarbazone-homoproline hybrids (H2L2) were synthesised. By reaction of H2L1 with NiCl2·6H2O, PdCl2 and CuCl2·2H2O in ethanol, the series of square-planar complexes [Ni(H2L1)Cl]Cl·1.3H2O (1·1.3H2O), [Pd(H2L1)Cl]Cl·H2O (2·H2O) and [Cu(H2L1)Cl]Cl·0.7H2O (3·0.7H2O) was prepared, and starting from H2L2 and CuCl2·2H2O in methanol, the complex [Cu(H2L2)Cl2]·H2O (4·H2O) was obtained. The compounds have been characterised by elemental analysis, spectroscopic methods (IR, UV-vis and NMR spectroscopy), ESI mass spectrometry and single crystal X-ray crystallography (H2L1, 1, 2 and 4). As a solid, 1 is diamagnetic, while it is paramagnetic in methanolic solution. The effective magnetic moment of 3.26 B.M. at room temperature indicates the change in coordination geometry from square-planar to octahedral upon dissolution. The in vitro anticancer potency of ligand precursors H2L1 and H2L2 and metal complexes 1–4 was studied in three human cancer cell lines (A549, CH1 and SW480) and in noncancerous murine embryonal fibroblasts (NIH/3T3), and the mechanism of cell death was also assayed by flow cytometry. Clear-cut structure–activity relationships have been established. The metal ions exert marked effects in a divergent manner: copper(ii) increases, whereas nickel(ii) and palladium(ii) decrease the cytotoxicity of the hybrids. The antiproliferative activity of H2L1 and metal complexes 1–3 decreases in all three tumour cell lines in the following rank order: 3 ＞ H2L1 ＞ 1 ＞ 2. The role of square-planar geometry in the underlying mechanism of cytotoxicity of the metal complexes studied seems to be negligible, while structural modifications at the terminal amino group of thiosemicarbazide and proline moieties are significant for enhancing the antiproliferative activity of both hybrids and copper(ii) complexes. [ABSTRACT FROM AUTHOR]

A series of heteropentanuclear oxalate-bridged Ru(NO)-Ln (4d-4f) metal complexes of the general formula ( nBu4N)5[Ln{RuCl3(μ-ox)(NO)}4], where Ln=Y ( 2), Gd ( 3), Tb ( 4), Dy ( 5) and ox=oxalate anion, were obtained by treatment of ( nBu4N)2[RuCl3(ox)(NO)] ( 1) with the respective lanthanide salt in 4:1 molar ratio. The compounds were characterized by elemental analysis, IR spectroscopy, electrospray ionization (ESI) mass spectrometry, while 1, 2, and 5 were in addition analyzed by X-ray crystallography, 1 by Ru K-edge XAS and 1 and 2 by 13C NMR spectroscopy. X-ray diffraction showed that in 2 and 5 four complex anions [RuCl3(ox)(NO)]2− are coordinated to YIII and DyIII, respectively, with formation of [Ln{RuCl3(μ-ox)(NO)}4]5− (Ln=Y, Dy). While YIII is eight-coordinate in 2, DyIII is nine-coordinate in 5, with an additional coordination of an EtOH molecule. The negative charge is counterbalanced by five nBu4N+ ions present in the crystal structure. The stability of complexes 2 and 5 in aqueous medium was monitored by UV/Vis spectroscopy. The antiproliferative activity of ruthenium-lanthanide complexes 2- 5 were assayed in two human cancer cell lines (HeLa and A549) and in a noncancerous cell line (MRC-5) and compared with those obtained for the previously reported Os(NO)-Ln (5d-4f) analogues ( nBu4N)5[Ln{OsCl3(ox)(NO)}4] (Ln=Y ( 6), Gd ( 7), Tb ( 8), Dy ( 9)). Complexes 2- 5 were found to be slightly more active than 1 in inhibiting the proliferation of HeLa and A549 cells, and significantly more cytotoxic than 5d-4f metal complexes 6- 9 in terms of IC50 values. The highest antiproliferative activity with IC50 values of 20.0 and 22.4 μ M was found for 4 in HeLa and A549 cell lines, respectively. These cytotoxicity results are in accord with the presented ICP-MS data, indicating five- to eightfold greater accumulation of ruthenium versus osmium in human A549 cancer cells. [ABSTRACT FROM AUTHOR]

Stoichiometry and stability of GaIII, FeIII, FeIIcomplexes of Triapine and five related α-Nheterocyclic thiosemicarbazones with potential antitumor activity have been determined by pH-potentiometry, UV-vis spectrophotometry, 1H NMR spectroscopy, and spectrofluorimetry in aqueous solution (with 30% DMSO), together with the characterization of the proton dissociation processes. Additionally, the redox properties of the iron complexes were studied by cyclic voltammetry at various pH values. Formation of high stability bis-ligand complexes was found in all cases, which are predominant at physiological pH with FeIII/FeII, whilst only at the acidic pH range with GaIII. The results show that among the thiosemicarbazones with various substituents the N-terminal dimethylation does not exert a measurable effect on the redox potential, but has the highest impact on the stability of the complexes as well as the cytotoxicity, especially in the absence of a pyridine-NH2group in the molecule. In addition the fluorescence properties of the ligands in aqueous solution and their changes caused by GaIIIwere studied. [ABSTRACT FROM AUTHOR]

The macrocyclisation reaction of 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) (1) with S-methylisothiosemicarbazide hydroiodide (H2NNC(SCH3)NH2·HI) in the presence of potassium triflate, followed by addition of M(CH3COO)2·nH2O, where M=Ni, Cu, Zn, afforded [NiLKI3] (2), [NiLK(CF3SO3)] (3), [CuLK(CF3SO3)(CH3OH)] (4) and [(ZnILK)2CH3OH] (5), respectively. Compounds 2–5 have been characterised by X-ray crystallography. IR, electronic, mass, 1H, 13C{1H} and 19F{1H} NMR spectra are reported. Magnetic susceptibility measurements and ESR spectra of 4 indicate weak intermolecular spin–spin interactions, which are mostly dipolar in origin. [Copyright &y& Elsevier]

Abstract: Two p-cymene ruthenium chlorido complexes containing isobutyl (C1) and isoamyl (C2) esters of (S,S)-ethylenediamine-N,N′-di-2-(3-cyclohexyl)propanoic acid as ligands were prepared from p-cymene ruthenium dichloride dimer and corresponding ester. All compounds have been characterized by elemental analysis, IR, ESI-MS, 1H and 13C NMR spectroscopy. Single crystal X-ray structure diffraction analysis of C1 shows the usual piano-stool geometry of complexes, with coordination of ester ligand via nitrogen donor atoms. Ligands exhibit moderate anticancer activity (IC50 > 50 μM), while the complexes were significantly more cytotoxic towards various cancer cell lines, including B16, A375, HCT116, A549 and MCF7 cells (IC50 min.–max. 2.9–8.0 μM). We stress that cisplatin resistant HCT116 cell line was highly sensitive to the treatment with C1 and C2 (IC50 values: 4.4 and 5.5 μM versus IC50 > 120 μM for cisplatin). In parallel, primary fibroblasts-MRC-5 were remarkably less affected by these compounds. [Copyright &y& Elsevier]

Abstract: A group of five phosphino hydrazones with a pendant binaphthyl unit as a chiral modifier has been synthesized from non-racemic 2,2′-bis(bromomethyl)-1,1′-binaphthyl and 3,3′-diiodo-2,2′-bis(bromomethyl)-1,1′-binaphthyl as the key intermediates. Their efficiency as chiral ligands in palladium-catalyzed allylic alkylation reactions has been investigated showing up to 95% ee under optimized conditions. X-ray diffraction structures of mono- and dimeric Pd complexes are also reported. [ABSTRACT FROM AUTHOR]

Three new gallium(III) and iron(III) complexes with l -proline-thiosemicarbazone hybrids, namely [GaCl( l -Pro-FTSC–2H)]·0.7H 2 O·0.5CH 3 OH ( 1 ·0.7H 2 O·0.5CH 3 OH), [GaCl(dm- l -Pro-FTSC–2H)]·0.4H 2 O ( 2 ·0.4H 2 O) and [FeCl( l -Pro-FTDA–H)]Cl ( 3 ) were synthesised and comprehensively characterised by spectroscopic methods ( 1 H, 13 C NMR, UV–vis), ESI mass spectrometry and X-ray crystallography. The complexes are soluble in biological media to allow for assaying their antiproliferative activity. The complexes were tested in three human cancer cell lines, namely HeLa, A549 (non-small cell lung cancer), LS174 and nontumorigenic MRC5. Complex formation equilibrium processes of l -Pro-FTSC with gallium(III), iron(II) and iron(II) ions were investigated in solution. The formation of mono-ligand iron(II) and gallium(III) complexes with pentadentate ligands and relatively low aqueous solution stability was found. Between iron(III) and the ligands, a redox reaction takes place via the oxidative cyclisation of the thiosemicarbazone. [ABSTRACT FROM AUTHOR]

Three new ruthenium(II)–arene halido complexes of general formula [(η 6 - p -cymene)RuX(L)] ( C1 C3 ) were synthesised by reaction of [(η 6 - p -cymene)RuX 2 ] 2 (X − = Cl − , Br − , I − ) with 1 H -benzimidazole-2-carboxylic acid (HL) in ethanol. The complexes were characterised by elemental analysis, mass spectrometry, IR, 1 H and 13 C NMR spectroscopy. The 1 H -benzimidazole-2-carboxylate was found to act as a bidentate N,O–chelating ligand. Single-crystal X-ray diffraction analysis confirmed the “piano-stool” geometry of C3 . The cytotoxic activity of the ligand precursor and ruthenium complexes was tested in human cancer cell lines: cervical carcinoma (HeLa), breast carcinoma (MDA-MB-231), myelogenous leukemia (K562) as well as in one normal human fetal lung fibroblast cell line (MRC-5), by MTT assay. The results show that ruthenium(II)-arene complexes possess enhanced cytotoxicity when compared to that of HL. The latter was devoid of activity in the range of concentrations up to 300 μM. Complex C3 , carrying an iodido leaving ligand, exhibited moderate, but selective cytotoxicity toward HeLa, MDA-MB-231 and K562 cell lines, with IC 50 values: 73.7, 60.9 and 53.9 μM, respectively, being less toxic against MRC-5 cells (IC 50 = 175.9 μM). Complexes C1 and C2 showed moderate to low cytotoxicity in HeLa and K562 cells. [ABSTRACT FROM AUTHOR]

Mononuclear nickel(II), copper(II), and manganese(III) complexes with a noninnocent tetradentate Schiff base ligand containing a disiloxane unit were prepared in situ by reaction of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane followed by addition of the appropriate metal(II) salt. The ligand H2L resulting from these reactions is a 2:1 condensation product of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane. The resulting metal complexes, NiL·0.5CH2Cl2, CuL·1.5H2O, and MnL(OAc)·0.15H2O, were characterized by elemental analysis, spectroscopic methods (IR, UV-vis, X-band EPR, HFEPR, ¹H NMR), ESI mass spectrometry, and single crystal X-ray diffraction. Taking into account the well-known strong stabilizing effects of tert-butyl groups in positions 3 and 5 of the aromatic ring on phenoxyl radicals, we studied the one-electron and two-electron oxidation of the compounds using both experimental (chiefly spectroelectrochemistry) and computational (DFT) techniques. The calculated spin-density distribution and localized orbitals analysis revealed the oxidation locus and the effect of the electrochemical electron transfer on the molecular structure of the complexes, while time-dependent DFT calculations helped to explain the absorption spectra of the electrochemically generated species. Hyperfine coupling constants, g-tensors, and zero-field splitting parameters have been calculated at the DFT level of theory. Finally, the CASSCF approach has been employed to theoretically explore the zero-field splitting of the S = 2 MnL(OAc) complex for comparison purposes with the DFT and experimental HFEPR results. It is found that the D parameter sign strongly depends on the metal coordination geometry. [ABSTRACT FROM AUTHOR]

The acid-base properties of 1,5-bis(2-hydroxybenzaldehyde)carbohydrazone (H 4 L) and its thioanalogue 1,5-bis(2-hydroxybenzaldehyde)thiocarbohydrazone (H 4 L S ) have been studied experimentally by pH-potentiometry and UV-Vis spectrophotometry and theoretically by using DFT methods. Copper(II) complexes [Cu 2 (HL)(DMSO) 2 (H 2 O)]NO 3 ·H 2 O ( 1 ), [{Cu 2 (HL)(DMF)(H 2 O)} n ][{Cu 2 (HL)(DMF)NO 3 } n ](NO 3 ) n ( 2 ), [Cu 2 (HL)(DMF) 2 (H 2 O)]HSO 4 ·H 2 O ( 3 ), [Cu 2 (HL)(DMF) 2 (H 2 O)][Cu 2 (HL)(SO 4 )(H 2 O)(DMF) 2 ]·2H 2 O ( 4 ) and [Cu 4 (HL) 2 (HSO 4 )(DMF) 2 ]HSO 4 ( 5 ), where H 4 L = 1,5-bis(2-hydroxybenzaldehyde)carbohydrazone, have been synthesised. Complexes 1 - 3 have been characterised by elemental analysis, IR spectroscopy, ESI mass spectrometry, cyclic voltammetry, magnetic susceptibility measurements and X-ray diffraction, while 4 and 5 only by X-ray crystallography. X-ray diffraction revealed that the ditopic triply deprotonated ligand possesses two binding sites able to accommodate transition metal ions, namely ONN and ONO. Magnetic measurements showed antiferromagnetic interactions between copper(II) centres. [ABSTRACT FROM AUTHOR]

In this study, the indoloquinoline backbone and piperazine were combined to prepare indoloquinoline-piperazine hybrids and their ruthenium- and osmium-arene complexes in an effort to generate novel antitumor agents with improved aqueous solubility. In addition, the position of the metal-binding unit was varied, and the effect of these structural alterations on the aqueous solubility and antiproliferative activity of their ruthenium- and osmium-arene complexes was studied. The indoloquinoline-piperazine hybrids L1-3 were prepared in situ and isolated as six ruthenium and osmium complexes [(η6-p-cymene)M(L1-3)Cl]Cl, where L¹ = 6-(4-methylpiperazin-1-yl)-N-(pyridin-2-yl-methylene)-11H-indolo[3,2-c]quinolin-2-N-amine, M = Ru ([1a]Cl), Os ([1b]Cl), L² = 6-(4-methylpiperazin-1-yl)-N-(pyridin-2-yl-methylene)-11H-indolo[3,2-c]quinolin-4-N-amine, M = Ru ([2a]Cl), Os ([2b]Cl), L³ = 6-(4-methylpiperazin-1-yl)-N-(pyridin-2-yl-methylene)-11H-indolo[3,2-c]quinolin-8-N-amine, M = Ru ([3a]Cl), Os ([3b]Cl). The compounds were characterized by elemental analysis, one- and two-dimensional NMR spectroscopy, ESI mass spectrometry, IR and UV-vis spectroscopy, and single-crystal X-ray diffraction. The antiproliferative activity of the isomeric ruthenium and osmium complexes [1a,b]Cl-[3a,b]Cl was examined in vitro and showed the importance of the position of the metal-binding site for their cytotoxicity. Those complexes containing the metal-binding site located at the position 4 of the indoloquinoline scaffold ([2a]Cl and [2b]Cl) demonstrated the most potent antiproliferative activity. The results provide important insight into the structure-activity relationships of ruthenium- and osmium-arene complexes with indoloquinoline-piperazine hybrid ligands. These studies can be further utilized for the design and development of more potent chemotherapeutic agents. [ABSTRACT FROM AUTHOR]

Highlights: [•] Quasirelativistic study of electron density topology of Os and Ru complexes. [•] Electron/spin densities and negative Laplacian of electron density presented. [•] Analytic correction of picture change error at IOTC level. [•] Relativistic and spin–orbit effects are considered, IOTC vs. DKH2 compared. [Copyright &y& Elsevier]

Abstract: A series of seven new ruthenium(II)–arene complexes of general formula [Ru(η6-p-cymene)(L1−7)Cl], where L1−7 are fluoro, chloro, bromo or methyl derivatives of picolinic acid or isoquinoline-3-carboxylic acid has been synthesized and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy and ESI mass spectrometry. X-ray diffraction studies of two compounds showed the usual piano-stool geometry, with coordination of picolinato ligands through the pyridine nitrogen and the carboxylic group oxygen atom (N/COO− donor set). Cytotoxicity of complexes in vitro has been evaluated in three human tumor cell lines: cervix carcinoma (HeLa), melanoma (FemX), lung adenocarcinoma (A549) and one normal cell line (MRC-5). Complex with isoqinoline-3-carboxylic acid as ligand, exhibited significantly lower cytotoxic activity in normal cells (MRC-5) against high activity observed in panel of tumor cells and prominent cell type selectivity among tumor cells. [Copyright &y& Elsevier]

Dicopper(II) and dizinc(II) complexes [Cu2(McooCLCo°)-(CH3COO)2] (1) and [Zn2(MeocLcoo)(CH3COO)2] (2) were synthesized by reaction of Cu(CH3COO)2-H2O and Zn(CH3COO)2-2H2O with a new nonsymmetric dinucleating ligand ElOOCHLCOOEt prepared by condensation of 6-hydrazinyl-IIH-indolo[3,2-c]quinoline with diethyl-2,2'-((3-formyl-2-hydroxy-5-methylbenzyl)azanediyl)-diacetate. The design and synthesis of this elaborate ligand was performed with the aim of increasing the aqueous solubility of indolo[3,2-c]quinolines, known as biologically active compounds, and investigating the antiproliferative activity in human cancer cell lines and the cellular distribution by exploring the intrinsic fluorescence of the indoloquinoline scaffold. The compounds have been comprehensively characterized by elemental analysis, spectroscopic methods (IR, UV--vis,¹H and 13C NMR spectroscopy), ESI mass spectrometry, magnetic susceptibility measurements, and UV--vis complex formation studies (for l) as well as by X-ray crystallography (l and 2). The antiproliferative activity of EtOOCHLCOOEt, 1, and 2 was determined by the MTT assay in three human cancer cell lines, namely, A549 (nonsmall cell lung carcinoma), CHI (ovarian carcinoma), and SW480 (colon adenocarcinoma), yielding IC50 values in the micromolar concentration range and showing dependence on the cell line. The effect of metal coordination on cytotoxicity of EtOOCHLCOOEt is also discussed. The subcellular distribution of EtOOCHLCOOEt and 2 was investigated by fluorescence microscopy, revealing similar localization for both compounds in cytoplasmic structures. [ABSTRACT FROM AUTHOR]

Two proline-thiosemicarbazone bioconjugates with excellent aqueous solubility, namely, 3-methyl-(S)-pyrrolidine-2-carboxylate-2-formylpyridine thiosemicarbazone [l-Pro-FTSC or (S)-H2L] and 3-methyl-(R)-pyrrolidine-2-carboxylate-2-formylpyridine thiosemicarbazone [d-Pro-FTSC or (R)-H2L], have been synthesized and characterized by elemental analysis, one- and two-dimensional (1)H and (13)C NMR spectroscopy, and electrospray ionization mass spectrometry. The complexation behavior of l-Pro-FTSC with copper(II) in an aqueous solution and in a 30% (w/w) dimethyl sulfoxide/water mixture has been studied via pH potentiometry, UV-vis spectrophotometry, electron paramagnetic resonance, (1)H NMR spectroscopy, and spectrofluorimetry. By the reaction of copper(II) acetate with (S)-H2L and (R)-H2L in water, the complexes [Cu(S,R)-L] and [Cu(R,S)-L] have been synthesized and comprehensively characterized. An X-ray diffraction study of [Cu(S,R)-L] showed the formation of a square-pyramidal complex, with the bioconjugate acting as a pentadentate ligand. Both copper(II) complexes displayed antiproliferative activity in CH1 ovarian carcinoma cells and inhibited Topoisomerase IIα activity in a DNA plasmid relaxation assay. [ABSTRACT FROM AUTHOR]

Abstract: Six novel ruthenium(II)- and osmium(II)-arene complexes with indoloquinoline modified ligands containing methyl and halo substituents in position 8 of the molecule backbone have been synthesised and comprehensively characterised by spectroscopic methods (1H, 13C NMR, UV–Vis), ESI mass spectrometry and X-ray crystallography. Binding of indoloquinolines to a metal-arene scaffold makes the products soluble enough in biological media to allow for assaying their antiproliferative activity. The complexes were tested in three human cancer cell lines, namely A549 (non-small cell lung cancer), SW480 (colon carcinoma) and CH1 (ovarian carcinoma), yielding IC50 values in the 10−6–10−7 M concentration range after continuous exposure for 96h. Compounds with halo substituents in position 8 are more effective cytotoxic agents in vitro than the previously reported species halogenated in position 2 of the indoloquinoline backbone. High antiproliferative activity of both series of substances may be due at least in part to their potential to act as DNA intercalators. [Copyright &y& Elsevier]

Abstract: In an attempt to combine the ability of indolobenzazepines (paullones) to inhibit cyclin-dependent kinases (Cdks) and that of platinum-group metal ions to interact with proteins and DNA, ruthenium(II) and osmium(II) arene complexes with paullones were prepared, expecting synergies and an increase of solubility of paullones. Complexes with the general formula [MIICl(η 6-p-cymene)L]Cl, where M=Ru (1, 3) or Os (2, 4), and L= L 1 (1, 2) or L 2 (3, 4), L 1 = N-(9-bromo-7,12-dihydroindolo[3,2-d][1]-benzazepin-6(5H)-yliden-N′-(2-hydroxybenzylidene)azine and L 2 = N-(9-bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-yl)-N′-[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl-methylene]azinium chloride (L 2 *HCl), were now investigated regarding cytotoxicity and accumulation in cancer cells, impact on the cell cycle, capacity of inhibiting DNA synthesis and inducing apoptosis as well as their ability to inhibit Cdk activity. The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay yielded IC50 values in the nanomolar to low micromolar range. In accordance with cytotoxicity data, the BrdU assay showed that 1 is the most and 4 the least effective of these compounds regarding inhibition of DNA synthesis. Effects on the cell cycle are minor, although concentration-dependent inhibition of Cdk2/cyclin E activity was observed in cell-free experiments. Induction of apoptosis is most pronounced for complex 1, accompanied by a low fraction of necrotic cells, as observed by annexin V–fluorescein isothiocyanate/propidium iodide staining and flow cytometric analysis. [Copyright &y& Elsevier]

A one-pot synthesis of osmium(IV) complexes with two different tautomers of indazole, 1 H -indazole and 2 H -indazole, namely (H 2 ind)[Os IV Cl 5 (2 H- ind)] ( 1 ) and (H 2 ind)[Os IV Cl 5 (1 H- ind)] ( 2 ) is reported. Both compounds have been comprehensively characterized by NMR spectroscopy, ESI (electrospray ionization) mass spectrometry, electronic absorption spectroscopy, IR spectroscopy, cyclic voltammetry and tested for antiproliferative activity in vitro in three human cancer cell lines, CH1 (ovarian carcinoma), A549 (non-small cell lung cancer) and SW480 (colon carcinoma), as well as in vivo in a Hep3B SCID mouse xeno-transplantation model. 2 H -Indazole tautomer stabilization in 1 has been confirmed by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract: Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone, 3-AP) is currently the most promising chemotherapeutic compound among the class of α-N-heterocyclic thiosemicarbazones. Here we report further insights into the mechanism(s) of anticancer drug activity and inhibition of mouse ribonucleotide reductase (RNR) by Triapine. In addition to the metal-free ligand, its iron(III), gallium(III), zinc(II) and copper(II) complexes were studied, aiming to correlate their cytotoxic activities with their effects on the diferric/tyrosyl radical center of the RNR enzyme in vitro. In this study we propose for the first time a potential specific binding pocket for Triapine on the surface of the mouse R2 RNR protein. In our mechanistic model, interaction with Triapine results in the labilization of the diferric center in the R2 protein. Subsequently the Triapine molecules act as iron chelators. In the absence of external reductants, and in presence of the mouse R2 RNR protein, catalytic amounts of the iron(III)–Triapine are reduced to the iron(II)–Triapine complex. In the presence of an external reductant (dithiothreitol), stoichiometric amounts of the potently reactive iron(II)–Triapine complex are formed. Formation of the iron(II)–Triapine complex, as the essential part of the reaction outcome, promotes further reactions with molecular oxygen, which give rise to reactive oxygen species (ROS) and thereby damage the RNR enzyme. Triapine affects the diferric center of the mouse R2 protein and, unlike hydroxyurea, is not a potent reductant, not likely to act directly on the tyrosyl radical. [Copyright &y& Elsevier]

Abstract: Microemulsion electrokinetic chromatography (MEEKC) offers a valuable tool for the rapid and highly productive determination of lipophilicity for metal-based anticancer agents. In this investigation, the MEEKC technique was applied for estimation of n-octanol–water partition coefficient (log P oct) of a series of antiproliferative complexes of gallium(III) and iron(III) with 4 N-substituted α-N-heterocyclic thiosemicarbazones. Analysis of relationships between the experimental log P oct and the retention factors of compounds showed their satisfactory consistency in the case of single metal sets, as well as for both metals. Since none of available calculation programs allows for evaluating the contribution of central metal ion into log P oct (i.e. Δlog P oct) of complexes of different metals, this parameter was measured experimentally, by the standard ‘shake-flask’ method. Extension of the log P oct programs by adding Δlog P oct data resulted in good lipophilicity predictions for the complexes of gallium(III) and iron(III) included in one regression set. Comparison of metal-thiosemicarbazonates under examination in terms of log P oct vs. antiproliferative activities (i.e. 50% inhibitory concentration in cancer cells) provided evidence that their cytotoxic potency is associated with the ability to cross the lipid bilayer of the cell-membrane via passive diffusion. [Copyright &y& Elsevier]

Abstract: Ru(II)–η 6-p-cymene compounds bearing pyrone-derived ligands, which were obtained by Mannich reaction with piperidine and related analogues, have been synthesized. The compounds were characterized by NMR spectroscopy, mass spectrometry, thermogravimetric analysis and in the case of 2-(2,6-dimethyl-morpholin-4-ylmethyl)-3-hydroxy-6-hydroxymethyl-pyran-4-one by X-ray diffraction analysis. The chlorido complexes are prone to aquation in aqueous solution which results in the formation of dimers. Dimer formation can be inhibited by in situ replacement of the chlorido ligand by imidazole yielding compounds which are significantly more stable in water, as demonstrated by 1H NMR spectroscopy. [Copyright &y& Elsevier]

Abstract: Ruthenium(II)–arene complexes of general formulae [(η6-p-cymene)Ru(L1–3)Cl2], where L1–3 is 3-acetylpyridine (1), 4-acetylpyridine (2) and 2-amino-5-chloropyridine (3), correspondingly, [(η6-p-cymene)Ru(HL4,5)Cl2], where HL4 and HL5 are respectively isonicotinic acid (4) and nicotinic acid (5) and [(η6-p-cymene)Ru(HL6–9)Cl], where H2L6–9 represent 2,3-pyridinedicarboxylic acid (6), 2,4-pyridinedicarboxylic acid (7), 2,5-pyridinedicarboxylic acid (8) and 2,6-pyridinedicarboxylic acid (9), were prepared by the reaction of [(η6-p-cymene)2RuCl2]2 (10) with the corresponding ligand in 1:2 molar ratio in isopropanol. The complexes were characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopies. According to these data the molecules adopt the usual “three-leg piano-stool” geometry which is common for this type of complexes. The structures of 1 and 7 were determined by X-ray crystallography. The complexes revealed low antiproliferative activity in six investigated tumor cell lines (HeLa, B16, FemX, MDA-MB-361, MDA-MB-453 and LS-174). The reaction of 6 with 9-methyladenine was studied by 1H NMR, 1H, 1H COSY and 1H, 1H NOESY spectroscopy. [Copyright &y& Elsevier]

Abstract: Organometallic ruthenium(II)-arene complexes coordinated to maltol-derived ligands were prepared and their anticancer activity against human tumor cell lines was studied. In addition, their hydrolysis behavior and reaction with 5′-GMP was tested and compared to the parent compound chlorido[2-methyl-3-(oxo-κO)-pyran-4(1H)-onato-κO4](η6-p-cymene)ruthenium(II) (Ru-maltol). Improved stability and in vitro anticancer activity at maintained GMP binding capability were observed, in comparison to the Ru-maltol complex. [Copyright &y& Elsevier]