Complex compounds of Pd(II), Pt(II), Ni(II), Hg(II) and Cu(I) with 1-benzylidene-2-phenazinoylhydrazine

Synthesis and physical-chemistry characterization of five new genuine complex compounds of 1-Benzylidine-2-phenazinoylhydrazine with Pd(II), Pt(II), Ni(II), Hg(II) and Cu(I) are presented. The chemical structure for these complexes is suggested by the elemental chemical analysis, molecular mass measurements, electric conductivities as well as by IR and UV-VIS spectra. The metal:ligand molar ratio is found 1:1, the obtained complexes belonging to the square planar geometry D4h.     

Synthesis, characterization and biological activity evaluation of Pt(II), Pd(II), Co(III) and Ni(II) complexes with N-heteroaromatic selenosemicarbazones

Five new complexes of Pt(II), Pd(II), Co(III) and Ni(II) with 2-pyridine(quinoline)carboxaldehyde selenosemicarbazones were synthesized and characterized. Crystal structures of Pt(II) complex with the pyridine derivative and Co(III) complex with the quinoline derivative were determined. In all complexes the ligands were coordinated through N₂Se donor atom set forming either square-planar (Pt, Pd) or octahedral (Co, Ni) geometry. All complexes showed biological activity.     

Computational molecular characterization of the flavonoid Morin and its Pt(II), Pd(II) and Zn(II) complexes

In this work, we make use of a model chemistry within density functional theory (DFT) recently presented, which is called M05-2X, to calculate the molecular structure of the flavonoid Morin and its Pt(II), Pd(II) and Zn(II) complexes, as well to predict their IR and UV-Vis spectra, the dipole moment and polarizability, the free energy of solvation in different solvents as an indication of solubility, the HOMO and LUMO orbitals, and the chemical reactivity parameters that arise from Conceptual DFT. The calculated values are compared with the available experimental data for these molecules.     

Mixed complexes of Pt(II) and Pd(II) with ethylsarcosinedithiocarbamate and 2-/3-picoline as antitumor agents

The [M(ESDT)Cl](n) (M=Pt(II), Pd(II); ESDT=EtO(O)CCH(2)N(CH(3))CS(2)(-), ethylsarcosinedithiocarbamate ion) species have been reacted with 2- or 3-picoline in dichloromethane in order to obtain mixed ligand complexes of the type [M(ESDT)(L)Cl] (L=2-picoline, 3-picoline). The synthesized compounds have been isolated, purified and characterized by means of elemental analyses, (1)H-/(13)C-/(1)H(13)C-HMBC (heteronuclear multiple bonding coherence) NMR and FT-IR spectroscopy. The biological activity of the compounds reported here has been then determined in terms of cell growth inhibition, DNA synthesis inhibition, detection of interstrand cross-links and DNA-protein cross-links, and micronuclei (MN) detection on a panel of tumor cell lines both sensitive and resistant to cisplatin. On the basis of the experimental results, coordination in the above mentioned complexes takes place in a near square-planar geometry, the dithiocarbamate moiety acting as a chelating agent, whereas the two remaining coordination sites are occupied by a chlorine atom and an amino ligand. Above all, [Pt(ESDT)(2-picoline)Cl] complex has shown very encouraging cytotoxicity levels higher or, at least, comparable to those exerted by cisplatin in the same experimental conditions.     

Preparation, characterization and pH-metric measurements of 4-hydroxysalicylidenechitosan Schiff-base complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(III), Rh(III), Pd(II) and Au(III)

The 4-hydroxysalicylidenechitosan Schiff-base (2CS-Hdhba) was prepared by the condensation of 2,4-dihydroxybenzaldehyde with chitosan, and its metal complexes, [M(2CS-dhba)Cl₂(H₂O)₂] (M(III) = Fe, Ru, Rh), [M′(2CS-dhba)(AcO)(H₂O)₂] (M′(II) = Co, Ni, Cu, Zn), [Pd(2CS-dhba)Cl(H₂O)] and [Au(2CS-dhba)Cl₂], are reported. These complexes were characterized by elemental analysis, by spectral data (FTIR, solid-phase ¹³C NMR, UV–vis and ESR spectroscopy), by morphological observations (SEM and XRD), and by magnetic and thermal measurements. The Schiff base (2CS-Hdhba) behaves as a bidentate chelate with a single negative charge. The azomethine nitrogen and the deprotonated 2-hydroxy centres with the pendant glucosamine hydroxy functionality play no role in coordination. The dissociation constants of 2CS-Hdhba and the stability constants of some of its metal complexes have been determined pH-metrically.     

Coordination versatility of 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane: Co(II) and Ni(II) complexes

The ligand 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane (L⁸) has afforded six-coordinate monomeric and dimeric complexes [(L⁸)Co^II(H₂O)₂][ClO₄]₂ (1), [(L⁸)Ni^II(MeCN)₂][BPh₄]₂ (2), [(L⁸)Ni^II(O₂CMe)][BPh₄] (3), and . The crystal structures of 1, 2 · MeCN, 3, and 4 revealed that the ligand L⁸ is flexible enough to expand its coordinating ability by fine-tuning the angle between the chelating fragments and hence folds around cobalt(II)/nickel(II) centers to act as a tetradentate chelate, allowing additional coordination by two trans-H₂O, cis-MeCN, and a bidentate acetate affording examples of distorted octahedral , , and coordination. The angles between the two CoN₂/NiN₂ planes span a wide range 23.539(1)° (1), 76.934(8)° (2), and 69.874(14)° (3). In contrast, complex 4 is a bis-μ-1,3-acetato-bridged (syn-anti coordination mode) dicobalt(II) complex [Co?Co separation: 4.797(8) Å] in which L⁸ provides terminal bidentate pyridylpyrazole coordination to each cobalt(II) center. To our knowledge, this report provides first examples of such a coordination versatility of L⁸. Absorption spectral studies (MeCN solution) have been done for all the complexes. Complexes 1-3 are uniformly high-spin. Temperature-dependent (2-300 K) magnetic studies on 4 reveal weak ferromagnetic exchange coupling between two cobalt(II) (S = 3/2) ions. The best-fit parameters obtained are: Δ (axial splitting parameter) = −765(5) cm⁻¹, λ (spin-orbit coupling) = −120(3) cm⁻¹, k (orbital reduction factor) = 0.93, and J (magnetic exchange coupling constant) = +1.60(2) m⁻¹.     

Cu, Pt, and Pd complexes of the 3-deoxy-1,2-bis(thiosemicarbazone) derived from D-glucose

3-Deoxy-D-erythro-hexos-2-ulose bis(thiosemicarbazone) (1) acts as a tetradentate ligand of the N2S2 type which forms stable coordination complexes with metal(II) cations. The Cu(II), Pt(II), and Pd(II) chelates (2, 4, and 6, respectively) of 1 were synthesized and characterized by elemental analysis and NMR spectroscopy. The NMR spectra of the Pt complex (4) showed the coupling of H-1 and C-1, C-2 of the bis(thiosemicarbazone) with 195Pt (33.7% naturally occurring), which supports the structure proposed for the chelate. The complexes 2, 4, and 6 were acetylated to give the corresponding tri-O-acetyl derivatives 3, 5, and 7. Elimination of Cu(II) from 3 with hydrogen sulfide afforded 8, the tri-O-acetyl derivative of 1. Preliminary studies have shown antiviral activity of chelates 2, 4, and 6 against poliovirus type 1.     

Complex compounds of Pd(II), Pt(II), Cu(I) and Hg(II) with tertiary thioamides

Synthesis and chemical and physical characterization of four new complex compounds of thiobenzpyrolidide [1-(pyrolidine)-thiobenzoyl] with Pd(II), Pt(II), Cu(I) and Hg(II) are presented. The purposed chemical structure for these complexes is suggested by the elemental chemical analysis, molecular mass measurements, electric conductivities as well as by UV-VIS and IR spectra. The obtained compounds may in principle be used as enzyme inhibitors having a pronounced insecticidal action.     

Antiproliferative activity of Pt(II) and Pd(II) phosphine complexes with thymine and thymidine

Oxidative addition reactions between [M(PPh(3))(4)] (M=Pt and Pd) and N1-methylthymine (t)/3',5'-di-O-acetylthymidine (T) were carried out to give [M(II)(PPh(3))(2)Cl t (or T)] complexes, in which the metal is coordinated to the N3 of the base. All complexes were characterized by spectroscopic analyses (IR, NMR) and Fast Atom Bombardment mass spectrometry (FAB-MS); X-ray data for the thymine complexes and elemental analysis for the thymidine complexes are reported. The antiproliferative activity of the complexes was tested on human chronic myelogenous leukaemia K562 cells. Arrested polymerase-chain reaction analysis was carried on to correlate antiproliferative activity and inhibition of DNA replication. All Pd and Pt complexes exhibit antiproliferative activity, Pd complexes resulting always more active than Pt complexes. Arrested PCR data are strongly in agreement with the effects on cell growth, suggesting that inhibition of the DNA replication by the synthesized compounds is the major basis for their in vitro antiproliferative activity.     

N-benzoyl-N'-alkylthioureas and their complexes with Ni(II), Co(III) and Pt(II) - crystal structure of 3-benzoyl-1-butyl-1-methyl-thiourea: activity against fungi and yeast

The thiourea derivatives of N-butylmethylamine (3-benzoyl-1-butyl-1-methyl-thiourea) (1), N-ethylisopropylamine (3-benzoyl-1-ethyl-1-isopropyl-thiourea) (2) and the corresponding complexes of 1 and 2 with Ni(II), Co(III) and Pt(II) have been synthesized. The compounds obtained were characterized by elemental analysis, spectroscopic methods (FT-IR, UV-Vis and NMR) and mass spectrometry. Compound 1, crystallized in the triclinic space group. The antifungal activities of compounds 1 and 2 and their corresponding complexes against the fungus Penicillium digitatum and against the yeast Saccharomyces cerevisiae were investigated. In general, fungal growth inhibition was higher with compound 1 and its complexes than with compound 2, except for the Co(III) complex of 2.     

Preparation, separation and characterisation of two regioisomers of a N-hydroxyalkylpyridylpyrazole ligand: A structural investigation of their coordination to Pd(II), Pt(II) and Zn(II) centres

The reaction of the β-diketone 1-phenyl-3-(pyridyn-2-yl)propane-1,3-dione, and the monosubstituted hydrazine 2-hydroxyethylhydrazine has been investigated. Two regioisomers were identified, 2-(3-phenyl-5-(pyridyn-2-yl)-1H-pyrazol-1-yl)ethanol (pzol.1) and 2-(5-phenyl-3-(pyridyn-2-yl)-1H-pyrazol-1-yl)ethanol (pzol.2) in 57:43 ratio. The separation of the regioisomers was done by silica column chromatography using ethyl acetate as eluent.Palladium(II) and platinum(II), [MCl₂(pzol.1)₂], [MCl₂(pzol.2)], and zinc(II), [ZnCl₂(pzol.1)], [ZnCl₂(pzol.2)] complexes were synthesised and characterised. The crystals and molecular structures of [PdCl₂(pzol.2)]·H₂O and [ZnCl₂(pzol.2)] were solved by X-ray diffraction, and consist of mononuclear complexes. In complex [PdCl₂(pzol.2)]·H₂O, the Pd(II) centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine atoms in cis disposition. The pzol.2 ligand acts as a bidentate chelate forming a five-membered metallocycle ring. In complex [ZnCl₂(pzol.2)], the Zn(II) is five-coordinated with two Zn-N bonds (Zn-N_pz and Zn-N_py), one Zn-OH bond and two Zn-Cl bonds. The coordination geometry is intermediate between a trigonal bipyramid and a square pyramid. In this complex, the ligand pzol.2 is tridentated and forms two metallocycle rings.     

Crystal structures of Pt(II) and Pd(II) complexes with the free radical 4-aminoTEMPO

Pt(II) and Pd(II) compounds containing the free radical 4-aminoTEMPO (4amTEMPO) were synthesized and characterised by X-ray diffraction methods. The disubstituted complexes cis- and trans-Pt(4amTEMPO)₂I₂ were studied. The trans isomer was prepared from the isomerisation of the cis analogue. The two Pd(II) compounds trans-Pd(4amTEMPO)₂X₂ (X = Cl and I) were also characterised by crystallographic methods. A mixed-ligand complex cis-Pt(DMSO)(4amTEMPO)Cl₂ was synthesized from the isomerisation of the trans isomer in hot water. Its crystal structure was also determined. In all the complexes, the 4amTEMPO ligand is bonded to the metal through the -NH₂ group, since the nitroxide O atom is not a good donor atom for the soft Pt(II) and Pd(II) metals. The conformation of the 4-aminoTEMPO ligand was compared to those of the few reported structures in the literature.     

Equilibrium and structural studies on Co(II), Ni(II), Cu(II) and Zn(II) complexes with N-(2-benzimidazolyl)methyliminodiacetic acid: crystal structures of Ni(II) and Cu(II) complexes

Combined pH-metric, UV-Vis, ¹H NMR and EPR spectral investigations on the complex formation of M(II) ions (M=Co, Ni, Cu and Zn) with N-(2-benzimidazolyl)methyliminodiacetic acid (H₂bzimida, hereafter H₂L) in aqueous solution at a fixed ionic strength, I=10⁻¹ mol dm⁻³, at 25 ± 1 °C indicate the formation of M(L), M(H₋₁L)⁻ and M₂(H₋₁L)⁺ complexes. Proton-ligand and metal-ligand constants and the complex formation equilibria have been elucidated. Solid complexes, [M(L)(H₂O)₂] · nH₂O (n=1 for M = Co and Zn, n=2 for M = Ni) and {Cu (μ-L) · 4H₂O}_n, have been isolated and characterized by elemental analysis, spectral, conductance and magnetic measurements and thermal studies. Structures of [Ni(L)(H₂O)₂] · 2H₂O and {Cu(μ-L) · 4H₂O}_n have been determined by single crystal X-ray diffraction. The nickel(II) complex exists in a distorted octahedral environment in which the metal ion is coordinated by the two carboxylate O atoms, the amino-N atom of the iminodiacetate moiety and the pyridine type N-atom of the benzimidazole moiety. Two aqua O atoms function as fifth and sixth donor atoms. The copper(II) complex is made up of interpenetrating polymeric chains of antiferromagnetically coupled Cu(II) ions linked by carboxylato bridges in syn-anti (apical-equatorial) bonding mode and stabilized via interchain hydrogen bonds and π-π stacking interactions.     

Metal complexes of cyclic hydroxamates. Synthesis and crystal structures of 3-hydroxy-2-methyl-3H-quinazolin-4-one (ChaH) and of its Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes

The attempted acetylation of anthranilic hydroxamic acid (2-aminobenzohydroxamic acid) as a possible dual inhibitor of the catalytic sites in prostaglandin-H-synthase (PGHS) gave the cyclic hydroxamic acid 3-hydroxy-2-methyl-3H-quinazolin-4-one (ChaH) which was characterised by spectroscopy and X-ray crystallography. The length of the hydroxamic acid C-N bond, 1.3998(17) Å, in ChaH is longer than normal (∼1.33 Å) indicative of reduced delocalisation of the nitrogen lone pair of electrons into the hydroxamic acid π system. This is confirmed by the appearance of the ν(CO) band at a considerably higher wavenumber in the IR spectrum than normal. The complexes Fe(Cha)₂(Cl)(H₂O)·⁷/₂H₂O, Co(Cha)₂(EtOH)₂, Ni(Cha)₂(EtOH)₂, Cu(Cha)(H₂O)(Cl) and Zn(Cha)₂(H₂O), have been synthesised and their structures determined by X-ray crystallography. The X-ray data confirmed coordination by Cha^- through the carbonyl and deprotonated hydroxamate oxygen in all cases. The M-O (hydroxamate) bonds are shorter than the M-O (carbonyl) bonds by between 0.0930 Å for the Co(II) complex and 0.0448 Å for the Ni(II) complex. The geometries of all complexes conform to the coordination requirements of the particular metal ion involved. Speciation studies for ChaH and its complexes with Ni(II) and Zn(II) were carried out using pH-metric methods. The results show that ChaH is much more acidic than related acyclic hydroxamic acids and that its metal complexes are correspondingly less stable.     

Transition metal-saccharide chemistry: d-glucose complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

Metal complexes of d-glucose (d-Glc) from large cation containing dibromo-dichloro salts of dipositive metals [NEt₄]₂[MBr₂Cl₂] (M = Mn, Co, Ni, Cu and Zn) and the disodium salt of glucose were synthesized from a MeOH:MeCN mixture. The complexes were characterized by UV-vis absorption, circular dichroism, IR and proton magnetic resonance spectroscopies, and by elemental analysis, and were found to be Na[M(d-Glc)(OMe)Cl]. Cyclic voltammetric studies of these complexes, in the acidic to neutral pH range, indicated no dissociation, even in highly acidic conditions.This paper is dedicated to Professor Richard H. Holm (Harvard University) on the occasion of his 60th birthday.     

Synthesis and characterisation of Pd(II) allyl complexes derived from the diterpene carvone

A series of cationic allyl complexes of Pd(II) derived from the diterpene carvone have been synthesised and characterised using the chelating ligands, bipyridine, 1,8-phenanthroline, neocuproin, S,S (-)-Chiraphos and R (+)-Binap as co-ligands. These complexes can be readily converted to new organic products in which one C---H bond of the allyl methyl has been substituted. The structure of a bipyridyl complex as its tetraphenyl borate salt has been determined via X-ray diffraction. 2-D NOESY studies on the Chiraphos and Binap complexes are reported. The Binap, but not the Chiraphos, complex reveals η³-η³η³ isomerisation at ambient temperature.     

Pd(II) and Pt(II) complexes with aromatic diamines: study of their interaction with DNA

Pd(II) and Pt(II) new complexes with simple aromatic diamines were synthesised and characterised with the aim of studying their possible antitumour activity. The aromatic diamines chosen were 2,3-diaminotoluene (2,3 dat), 3,4-diaminotoluene (3,4 dat), 4,5-diaminoxylene (4,5 dax) and 2,3-diaminophenol (2,3 dap). The complexes, of formulae cis-[MCl(2)(diamine)], were characterised by elemental analysis, conductivity measurements, 1H, 13C(1H) and 195Pt NMR spectroscopy. The X-ray crystal structure was also resolved for the palladium complexes with 2,3-diaminotoluene and 4,5-diaminoxylene. The DNA adduct formation of the eight new complexes synthesised was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the complexes on plasmid DNA pBR322 were also obtained. Values of IC50 were also calculated for the four platinum complexes against the cisplatin resistant tumour cell line A2780cisR.     

Synthesis, spectroscopic properties and structural characterisation of Pd(II) and Pt(II) complexes with 1,3,5-pyrazole derived ligands. Rotation around the metal-N bond

Reactions of ligands 1-ethyl-5-methyl-3-phenyl-1H-pyrazole (L¹) and 5-methyl-1-octyl-3-phenyl-1H-pyrazole (L²) with [PdCl₂(CH₃CN)₂ and K₂PtCl₄ gave complexes trans-[MCl₂(L)₂] (L = L¹, L²). The new complexes were characterised by elemental analyses, conductivity measurements, infrared, ¹H and ¹³C{¹H} NMR spectroscopies and X-ray diffraction. The NMR study of the complex [PdCl₂(L¹)₂], in CDCl₃ solution, is consistent with a very slow rotation of ligands around the Pd-N bond, so that two conformational isomers can be observed in solution (syn and anti). Different behaviour is observed for complexes [PdCl₂(L²)₂] and [PtCl₂(L)₂] (L = L¹, L²), which present an isomer in solution at room temperature (anti). The crystal structure of [PdCl₂(L¹)₂] complex is described, where the Pd(II) presents a square planar geometry with the ligands coordinated in a trans disposition.     

Pd(II)- and Pt(II)-cimetidine complexes. Crystal structure of trans-[Pt(N,S-cimetidine)(2)]Cl(2)(*)12H(2)O

The influence of cimetidine on patients under cisplatin treatment for cancer is controversial. It has moderate or no effects on several types of cancer and its effects on the nephrotoxicity induced by cisplatin are uncertain. To examine the binding properties and antiproliferative effects of the known anticancer noble metals, cimetidine (cim) was complexed to platinum(II) and palladium(II). The crystal structure of the Pt-cim compound shows two molecules of cimetidine coordinated to the metal through thioether sulfur and imidazolic nitrogen whereas spectroscopic studies in solution for Pd-cim reveal that the ratio of the metal to cimetidine is 1:1 with identical coordination environments. To determine the antitumor activity of the drugs, the interaction of the metallic complexes and free cimetidine with DNA was assessed. Their cytotoxic activity was compared with that of cisplatin.