New Au(III), Pt(II) and Pd(II) complexes with glycyl-containing homopeptides

Twelve new Au(III), Pt(II) and Pd(II) complexes with glycyl-containing homopeptides glycyl-glycine (G2), glycyl-glycyl-glycine (G3), glycyl-glycyl-gycyl-glycine (G4), glycyl-glycyl-glycyl-glycyl-glycine (G5) and glycyl-glycyl-glycyl-glycyl-glycyl-glycine (G6) have been synthesized, isolated and characterized spectroscopically and structurally by means of solid-state linear-dichroic infrared (IR-LD) spectroscopy of oriented colloids in nematic liquid crystal host, ¹H- and ¹³C-NMR, TGA and DSC, UV–Vis spectroscopy, EPR, ESI- and FAB mass spectrometry and HPLC tandem mass spectrometry (HPLC-MS/MS). Quantum chemical calculations are carried out with a view to obtain the structures and spectroscopic properties of the ligand and newly synthesized metal complexes.     

Computational Studies of Au(I) and Au(III) Anticancer MetalLodrugs: A Survey

Owing to the growing hardware capabilities and the enhancing efficacy of computational methodologies, computational chemistry approaches have constantly become more important in the development of novel anticancer metallodrugs. Besides traditional Pt-based drugs, inorganic and organometallic complexes of other transition metals are showing increasing potential in the treatment of cancer. Among them, Au(I)- and Au(III)-based compounds are promising candidates due to the strong affinity of Au(I) cations to cysteine and selenocysteine side chains of the protein residues and to Au(III) complexes being more labile and prone to the reduction to either Au(I) or Au(0) in the physiological milieu. A correct prediction of metal complexes’ properties and of their bonding interactions with potential ligands requires QM computations, usually at the ab initio or DFT level. However, MM, MD, and docking approaches can also give useful information on their binding site on large biomolecular targets, such as proteins or DNA, provided a careful parametrization of the metal force field is employed. In this review, we provide an overview of the recent computational studies of Au(I) and Au(III) antitumor compounds and of their interactions with biomolecular targets, such as sulfur- and selenium-containing enzymes, like glutathione reductases, glutathione peroxidase, glutathione-S-transferase, cysteine protease, thioredoxin reductase and poly (ADP-ribose) polymerase 1.     

Synthesis, characterisation and electrochemical behaviour of Cu(II), Co(II), Ni(II) and Zn(II) complexes derived from acetylacetone and p -anisidine and their antimicrobial activity

Neutral tetradentate N₂O₂ type complexes of Cu(II), Ni(II), Co(II) and Zn(II) have been synthesised using the Schiff base formed by the condensation of acetylacetone andp-anisidine. Microanalysis, molar conductance, magnetic susceptibility, IR, UV-Vis,¹ H NMR, CV and EPR studies have been carried out to determine the structure of the complexes. From the data, it is found that all the complexes possess square-planar geometry. The EPR spectrum of the copper complex in DMSO at 300 K and 77 K was recorded and its salient features are reported. All the title complexes were screened for antimicrobial activity by the well diffusion technique using DMSO as solvent. The minimum inhibitory concentration (MIC) values were calculated at 37°C for a period of 24 h. It has been found that all the complexes are antimicrobially active and show higher activity than the free ligand.     

Kinetics and mechanism of electroreduction of Pd(II) complexes

The kinetics and mechanism of processes of reduction of Pd(II) complexes with a number of inorganic (NH₃ , Cl^– , etc.) and organic (ethylenediamine, glycine, -alanine, etc.) ligands on a dropping-mercury electrode and a Pd electrode in solutions with various concentrations of ligands, hydrogen ions, and supporting electrolytes are reviewed. The nature of electrochemical and chemical steps of processes of reduction of various complexes of Pd(II) is discussed.Translated from Elektrokhimiya, Vol. 40, No. 12, 2004, pp. 1494–1502.Original Russian Text Copyright © 2004 by Kravtsov.     

Rhodium(III), palladium(II) and platinum(II) complexes of Bis(o-aminobenzenesulfonyl)ethylenediamine

New complexes of the formulae K₃[RhL ₃]·2 H₂O, [PdL]·H₂O and [M(LH₂)Cl₂] [whereM = Pd, Pt andLH₂ = bis(o-aminobenzenesulfonyl)ethylenediamine] have been prepared and characterized by conductivity measurements, thermogravimetric analysis, X-ray powder patterns and IR, Ligand Field and¹H-NMR spectroscopy.

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Rhodium(III), Palladium(II)- und Platin(II)-Komplexe mit Bis(o-aminobenzolosulfonyl)ethylendiamin (Kurze Mitteilung)

Zusammenfassung Neue Komplexe der allgemeinen Formeln K₃[RhL ₃]·2H₂O, [PdL]·H₂O und [M(LH₂)Cl₂] mitM = Pd, Pt undLH₂ = Bis(o-aminobenzolosulfonyl)ethylendiamin wurden dargestellt und mit Konduktionsmessungen, thermogravimetrischen Analysen, Röntgenstrukturanalysen, IR, Ligandfeld- und¹H-NMR-Spektroskopie charakterisiert.

     

三价金配合物抗肿瘤活性研究*

三价金配合物具有潜在的抗肿瘤活性,是目前金属药物领域的研究热点。本文按配位原子的不同总结了稳定三价金配合物的结构特征,按其生物活性的构效关系、生物靶点和作用机制综述了三价金配合物抗肿瘤活性研究的最新成果：配体的结构特点以及离去基团对三价金配合物的体外细胞毒性影响较大;介绍了用于检测三价金配合物与可能的生物靶分子之间的相互作用的多种物理和生物学方法,重点关注了相互作用的模式,如嵌入/静电吸引/共价结合等,并解释了三价金配合物抗肿瘤活性的原因。最后提出了一些研究新思路,以期有助于设计得到靶标明确的具有良好药理活性的抗肿瘤药物。     

The excited states of bipyridyl and phenanthroline complexes of Fe(III), Ru(II) and Ru(III): A molecular orbital study

The semiempirical zero-differential-overlap molecular orbital model which was shown in earlier papers in this series to give a good account of the charge transfer and -* spectra of Fe(II) complexes with conjugated ligands such as 2,2-bipyridyl and 1,10-phenanthroline is extended to complexes having openshell ground states, such as those of Fe(III), and to complexes of Ru(II) and Ru(III). The results are used to assign the observed charge transfer and intra-ligand absorption bands to specific orbital transitions. Observed and calculated intensities are in good agreement: reasons are advanced for the much lower intensity of the charge transfer bands in Ru(III) compared to Ru(II) complexes.     

Synthesis, spectral and structural studies of 1-ethoxycarbonyl-piperazine-4-carbodithioate and its Co(III), Zn(II) and Cd(II) complexes

The new complexes [Co(ecpzdtc)₃] (2) [Zn(ecpzdtc)₂(py)] (3) and [Cd(ecpzdtc)₂(py)]·H₂O (4) have been synthesized from sodium 1-ethoxycarbonyl-piperazine-4-carbodithioate [(Na⁺(ecpzdtc)⁻]. The ligand and the complexes have been characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. The [Zn(ecpzdtc)₂(py)] and [Cd(ecpzdtc)₂(py)]·H₂O complexes contain pyridine as the co-ligand. [Co(ecpzdtc)₃] (2) crystallizes in the monoclinic system, whereas [Zn(ecpzdtc)₂(py)] (3) and [Cd(ecpzdtc)₂(py)]·H₂O (4) crystallize in the triclinic system. The sulfur donor sites of the bidentate ligand chelate the metal center, forming a four-membered CS₂M ring. The cobalt complex has a distorted octahedral geometry, the zinc complex is almost between trigonal bipyramidal and square pyramidal, whereas the cadmium complex is square pyramidal. The crystal structures of all the complexes are stabilized by various types of inter and intramolecular hydrogen bonding.     

Kinetics and mechanism of the substitution reactions of some monofunctional Pd(II) complexes with different nitrogen-donor heterocycles

Substitution reactions of five monofunctional Pd(II) complexes, [Pd(terpy)Cl]⁺ (terpy = 2,2′;6′,2″-terpyridine), [Pd(bpma)Cl]⁺ (bpma = bis(2-pyridylmethyl)amine), [Pd(dien)Cl]⁺ (dien = diethylenetriamine or 1,5-diamino-3-azapentane), [Pd(Me₄dien)Cl]⁺ (Me₄dien = 1,1,7,7-tetramethyldiethylenetriamine), and [Pd(Et₄dien)Cl]⁺ (Et₄dien = 1,1,7,7-tetraethyldiethylenetriamine), with unsaturated N-heterocycles such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr), 1,2,4-triazole, pyrazole, pyrazine, and imidazole were investigated in aqueous 0.10 M NaClO₄ in the presence of 10 mM NaCl using variable-temperature stopped-flow spectrophotometry. The second-order rate constants k₂ indicate that the reactivity of the Pd(II) complexes decrease in the order [Pd(terpy)Cl]⁺ > [Pd(bpma)Cl]⁺ > [Pd(dien)Cl]⁺ > [Pd(Me₄dien)Cl]⁺ > [Pd(Et₄dien)Cl]⁺. The most reactive nucleophile of the heterocycles is pyrazine, while the slowest reactivity is with pyrazole. Activation parameters were determined for all reactions and negative entropies of activation, ΔS^≠, supporting an associative mode of substitution. The reactions between [Pd(bpma)Cl]⁺ and 1,2,4-triazole, pzI, and pzBr were also investigated by ¹H NMR to define the manner of coordination. These results could be useful for better explanation of structure-reactivity relationships of Pd(II) complexes as well as for the prediction of potential targets of Pd(II) complexes toward common N-heterocycles, constituents of biomolecules and different N-bonding pharmaceutical agents.     

Thermal and spectroscopic studies of terbium(III) and dysprosium(III) complexes with piperidin-4-ones

Terbium(III) and dysprosium(III) nitrate complexes with variously substituted 2,6-diphenylpiperidin-4-ones (L¹)-(L¹⁰) of general formula [Ln(L)(NO₃)₂(H₂O)₂]NO₃ have been synthesized. These complexes have been characterized by analytical, spectral and thermal studies. Molar conductance data show that these complexes are 1:1 electrolytes. The presence of two coordinated water molecules is confirmed by thermal and infrared spectral studies. IR spectral data indicate that piperidin-4-ones, in spite of having two coordinating sites, are monodentate, coordinating only through ring nitrogen. The IR and conductance data reveal the presence of two bidentate and one ionic nitrate groups. The nephelauxetic ratio (β), covalency factor (b^1/2) and Sinha’s parameter (δ) evaluated from electronic spectral data of dysprosium(III) complexes indicate a little covalency in metal-ligand bonding.     

Thermogravimetric and spectroscopic studies on La(III) and Ce(III) complexes with some thio-schiff bases

Solid complexes of five derivatives of thio-Schiff bases with La(III) and Ce(III) ions were prepared and characterized by elemental and thermogravimetric analyses. The suggested general formula of the solid complexes is [ML₂(H₂O)X]·2H₂O, whereM=trivalent lanthanide ion,L=Schiff base andX=Cl^? or ClO ₄ ^? . Information about the water of hydration, the coordinated water molecules, the coordination chemistry and the thermal stability of these complexes was obtained and is discussed. Additionally, a general scheme of thermal decomposition of the lanthanide-Schiff base complexes is proposed.     

Au(III) interaction with Methionine- and Histidine-containing peptides

Mononuclear Au(III) complexes of the peptides H-His-Met-OH (D) and H-Gly-Gly-Met-OH (T) and their N-protected forms Ac-His-Met-OH (Ac-D) and Ac-Gly-Gly-Met-OH (Ac-T) were structurally characterized by means of IR, MS and NMR. In the complexes with dipeptides [AuLCl₂]Cl (L = D or Ac-D), Au(III) is coordinated through S and imidazole N atoms from methionine and histidine fragments of the ligands forming macrochelate rings at mol ratio Au?:?L = 1?:?1. Additionally, Au(III) is coordinated by two terminal chloride ions in a square-planar arrangement. In complexes with the tripeptides [AuL′Cl] (L′ = T or Ac-T), however, the metal ion is coordinated in a tridentate fashion, through S and two N atoms, also at mol ratio M?:?L = 1?:?1. The fourth position of Au(III) is occupied by a Cl^? ligand.     

Heteroleptic half-sandwich Ru(II), Rh(III) and Ir(III) complexes based on 5-ferrocenyldipyrromethene

The synthesis and characterization of heteroleptic complexes with the formulations [(η⁶-arene)RuCl(fcdpm)] (η⁶-arene = C₆H₆, C₁₀H₁₄) and [(η⁵-C₅Me₅)MCl(fcdpm)] (M = Rh, Ir; fcdpm = 5-ferrocenyldipyrromethene) have been reported. All the complexes have been characterized by elemental analyses, IR, ¹H NMR and electronic spectral studies. Structures of [(η⁶-C₆H₆)RuCl(fcdpm)] and [(η⁶-C₁₀H₁₄)RuCl(fcdpm)] have been determined crystallographically. Chelating monoanionic linkage of fcdpm to the respective metal centres has been supported by spectral and structural studies. Further, reactivity of the representative complex [(η⁶-C₁₀H₁₄)RuCl(fcdpm)] with ammonium thiocyanate (NH₄SCN) and triphenylphosphine (PPh₃) have been examined.     

Synthesis and spectroscopic characterization of cobalt(II) thiosemicarbazone complexes

Thiosemicarbazone derivatives are formed on reaction between acetophenone, salicylaldehyde, benzophenone and/or 2-hydroxy-4-methoxybenzophenone and thiosemicarbazide or its N⁴H substituents (ethyl-, phenyl-, and p-chlorophenyl-). The ligands were investigated by elemental analysis and spectral (IR, ¹H?NMR and MS) studies. The formulas of the prepared complexes have been suggested by elemental analyses and confirmed by mass spectra. The coordination sites of each ligand were elucidated using IR spectra revealing bidentate and tridentate coordination. Different geometries for the complexes were proposed on the basis of electronic spectra and magnetic measurements. The complexes have been analyzed thermally (TG and DTG) and the kinetic parameters for some of their degradation steps were calculated.     

Modelling the use of lanthanides(III) as probes at calcium(II) binding sites in biological systems: Preparation and characterization of neodymium(III) and calcium(II) malonamato(-1) complexes

A bioinorganic approach into the problem of the isomorphous substitution of calcium(II) by lanthanide(III) ions in biological systems is discussed. Reactions of malonamic acid (H₂malm) with Ca^II and Nd^III sources under similar conditions yielded the compounds [Ca(Hmalm)₂]_n (1), [Nd(Hmalm)₂(H₂O)₂]_n(NO₃)_n (2) and [Nd(Hmalm)₂(H₂O)₂]_nCl_n·2nH₂O (3·2nH₂O). Their X-ray crystal structure data show that the malonamate(-1) ligand presents two different ligation modes and coordinates through the two carboxylate and the amide-O atoms, thus bridging three Ca^II ions in 1 and two Nd^III ions in 2 and 3·2nH₂O. Complex 1 is a 3D coordination polymer based on neutral repeating units, whereas 2 and 3·2nH₂O are 1D coordination polymers based on the same cationic repeating unit. Hydrogen bonding interactions further stabilize the 3D framework structure of 1 and assemble the 1D chains of 2 and 3·2nH₂O into 3D networks. The three complexes were characterized spectroscopically (IR, far-IR, and Raman) and the thermal decomposition of 2 and 3·2nH₂O was monitored by TG/DTA and TG/DTG measurements. Variable-temperature magnetic susceptibility data for 2 are also reported. The bioinorganic chemistry relevance of our results is discussed.     

Synthesis and characterization of Ni(II), Pd(II) and Pt(II) complexes of 2,4-diamino-5-(3, 4, 5-trimethoxybenzyl)pyrimidine complexes

The Ni(II), Pd(II) and Pt(II) complexes of 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (trimethoprim) have been synthesized and characterized by elemental analysis, electronic and IR spectroscopy, and magnetic susceptibility measurements. The single-crystal X-ray structure of the Ni(II) complex is reported. Ni(II) is coordinated to the N(1) atoms of two trimethoprim molecules that act as monodentates. Octahedral coordination around the nickel atom is completed by coordination to two molecules of methanol and two acetate ions. Pd(II) and Pt(II) complexes are square planar and the metal ions coordinate one molecule of trimethoprim, two chloride ions and a molecule of water.     

Complexation of niobium(V) with some bis-(β-diketones)

The complexes of niobium(V) with 2-phenyl-1,1,3,3-tetraacetylpropane and 2-phenyl-1,3-diacetyl-1,3-dibenzoylpropane were investigated by IR, UV,¹H-NMR, and magnetic measurements. Together with analytical data and determination of molecular weights a trimeric structure is proposed for both 1:1 complexes.

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Komplexierung von Niob(V) mit einigen Bis(-diketonen)

Zusammenfassung Es wurden die Komplexe von Niob(V) mit 2-Phenyl-1,1,3,3-tetraacetylpropan und 2-Phenyl-1,3-diacetyl-1,3-dibenzoylpropan untersucht. IR-, UV- und¹H-NMR-Spektren sowie magnetische Messungen zusammen mit analytischen Daten und Molekulargewichtsbestimmungen ergaben für beide 1:1 Komplexe eine trimere Struktur.

     

Six-membered ring chelate complexes of Pd(II) and Pt(II) derived from di-(2-pyridyl)pyrimidin-2-ylsulfanylmethane

Cis-[MLCl₂] complexes of di-(2-pyridyl)pyrimidin-2-ylsulfanylmethane ligand (L), where M = Pd (1), and M = Pt (2) have been synthesized. Reaction of 1 with L in presence of Na[BF₄] and hot acetonitrile produced the complex [PdL₂](BF₄)₂ (3). Complexes 1-3 and ligand L have been characterized by elemental analyses, IR and NMR spectroscopy. Crystal structures of 1, 3 and L were determined by single crystal X-ray diffraction analyses, showing nonplanar structures with the pyridinic rings twisted around the bridging carbon and the ipso carbon bonds. 1 and 3 displayed a bidentate coordination of L to the palladium atom with the formation of six-membered chelate rings, where the local geometry at palladium atom was distorted square planar. In 3 the palladium atom was coordinated to two dipyridyl ligands through two of the pyridinic nitrogen atoms to form a cationic complex stabilized by two tetrafluoroborate counter-ions.     

Synthesis,characterization and cytotoxicity of Pt(II), Pd(II), Cu(II) and Zn(II) complexes with 4’‐substituted terpyridine

Eight novel Pt(II), Pd(II), Cu(II) and Zn(II) complexes with 4’‐substituted terpyridine were synthesized and characterized by elemental analysis, UV, IR, NMR, electron paramagnetic resonance, high‐resolution mass spectrometry and molar conductivity measurements. The cytotoxicity of these complexes against HL‐60, BGC‐823, KB and Bel‐7402 cell lines was evaluated by MTT assay. All the complexes displayed cytotoxicity with low IC₅₀ values (<20 μm ) and showed selectivity. Complexes 3 , 5 , 7 and 8 exerted 9‐, 5‐, 12‐ and 7‐fold higher cytotoxicity than cisplatin against Bel‐7402 cell line. The cytotoxicity of complexes 3 , 5 , 6 , 7 and 8 was higher than that of cisplatin against BGC‐823 cell line. Complexes 3 , 7 and 8 showed similar cytotoxicity to cisplatin against KB cell line. Complex 7 exhibited higher cytotoxicity than cisplatin against HL‐60 cell line. Among these complexes, complex 7 demonstrated the highest in vitro cytotoxicity, with IC₅₀ values of 1.62, 3.59, 2.28 and 0.63 μm against HL‐60, BGC‐823, Bel‐7402 and KB cells lines, respectively. The results suggest that the cytotoxicity of these complexes is related to the nature of the terminal group of the ligand, the metal center and the leaving groups. Copyright © 2013 John Wiley & Sons, Ltd.     

Chalcone-derived thiosemicarbazones and their zinc(II) and gallium(III) complexes: spectral studies and antimicrobial activity

Chalcone-derived 3-phenyl-1-pyridin-2-ylprop-2-en-1-one thiosemicarbazone (HPyCTPh) (1), 3-(4-chlorophenyl)-1-pyridin-2-ylprop-2-en-1-one thiosemicarbazone (HPyCT4ClPh) (2), 3-(4-bromophenyl)-1-pyridin-2-ylprop-2-en-1-one thiosemicarbazone (HPyCT4BrPh) (3), and 3-(4-nitrophenyl-1-pyridin-2-ylprop-2-en-1-one thiosemicarbazone (HPyCT4NO₂Ph) (4) were obtained as well as their gallium(III) and zinc(II) complexes [Ga(PyCTPh)₂]NO₃ (Ga1), [Ga(PyCT4ClPh)₂]NO₃ (Ga2), [Ga(PyCT4BrPh)₂]NO₃ (Ga3), [Ga(PyCT4NO₂Ph)₂]NO₃ (Ga4), [Zn(PyCTPh)₂] (Zn1), [Zn(PyCT4ClPh)₂] (Zn2), [Zn(PyCT4BrPh)₂] (Zn3), and [Zn(PyCT4NO₂Ph)₂] (Zn4). The chalcones, thiosemicarbazones, and zinc(II) complexes were not active against Pseudomonas aeruginosa. The thiosemicarbazones proved to be more active than the parent chalcones against Staphylococcus aureus and Candida albicans. Coordination to zinc(II) resulted in activity improvement of most thiosemicarbazones against S. aureus. Coordination to gallium(III) significantly improved the antimicrobial activity of all thiosemicarbazones against the studied micro-organisms, suggesting this to be an effective strategy for antimicrobial activity enhancement.