Jose Maria Moreno

Synthesis and characterization of novel palladium(II) complexes of bis(thiosemicarbazone). Structure, cytotoxic activity and DNA binding of Pd(II)-benzyl bis(thiosemicarbazonate).

The preparation of palladium(II) complexes of 3,5-diacyl-1,2,4-triazole bis(thiosemicarbazone) (H2L2), 2,6-diacylpyridine bis(thiosemicarbazone) (H2L3) and benzyl bis(thiosemicarbazone) (H2L4) is described. The new complexes [PdCl2(H2L2)] (1), [PdCl2(H2L3)] (2) and [PdL4].DMF (3) have been characterized by elemental analyses and spectroscopic studies (IR, 1H NMR and UV-Vis). The crystal and molecular structure of PdL4.DMF (L = bideprotonated form of benzyl bis(thiosemicarbazone)) has been determined by single-crystal X-ray diffraction: green triclinic crystal, a = 10.258(5), b = 10.595(5), c = 11.189(5) A, alpha = 97.820(5), beta = 108.140(5), gamma = 105.283(5) degrees, space group P1, Z = 1. The palladium atom is tetracoordinated by four donor atoms (SNNS) from L4 to form a planar tricyclic ligating system. The testing of the cytotoxic activity of compound 3 against several human, monkey and murine cell lines sensitive (HeLa, Vero and Pam 212) and resistant to cis-DDP (Pam-ras) suggests that compound 3 might be endowed with important antitumor properties since it shows IC50 values in a microM range similar to those of cis-DDP [cis-diamminedichloroplatinum(II)]. Moreover, compound 3 displays notable cytotoxic activity in Pam-ras cells resistant to cis-DDP (IC50 values of 78 microM versus 156 microM, respectively). On the other hand, the analysis of the interaction of this novel Pd-thiosemicarbazone compound with DNA secondary structure by means of circular dichroism spectroscopy indicates that it induces on the double helix conformational changes different from those induced by cis-DDP.

SINGLY ANTI-ANTI CARBOXYLATE-BRIDGED ZIG-ZAG CHAIN COMPLEXES FROM A CARBOXYLATE-CONTAINING TRIDENTATE SCHIFF BASE LIGAND AND M(HFAC)2 M = MNII, NIII, AND CUII : SYNTHESIS, CRYSTAL STRUCTURE, AND MAGNETIC PROPERTIES

The reaction of M(hfac)2 with the tridentate Schiff base H2L (where H2L stands for the 1:1 condensation product of 2-imidazolecarboxaldehyde with β-alanine) leads to the complexes [M(HL)(hfac)]n [M = MnII, NiII, and CuII; hfac = hexafluoroacetylacetonate anion] (1–3). The structures of the complexes 1 and 3 have been solved by X-ray crystallographic methods. The structures are very similar and consist of infinite zig-zag chains, running parallel to the b axis, in which the metal ions are bridged sequentially by anti-anti carboxylate groups with intrachain metal–metal distances of 6.134 A for 1 and 6.239 A for 3. Each monodeprotonated HL ligand acts as a tridentate one to a metal(II) ion and as a monodentate one to a neighbouring metal(II) centre. Metal atoms exhibit distorted octahedral coordination spheres comprised of two oxygen atoms from the hexafluoroacetylacetonate ligand, three donor atoms from the HL ligand and the oxygen atom belonging to the carboxylate group of an adjacent molecule. The complexes 1–3 have been confirmed to be isomorphous and isostructural on the basis of X-ray powder diffraction and IR spectra. The magnetic properties of the three compounds were studied by susceptibility measurements as a function of the temperature and successfully analyzed in terms of the isotropic spin Hamiltonian for one-dimensional infinite chain systems to give the coupling parameters J = –0.91 cm−1, g = 2.03 (1); J = –13.2 cm−1, g = 2.24 (2); and J = 0.40 cm−1, g = 2.11 (3). The magnetic behaviour for all three complexes can be satisfactorily explained in terms of the conformation of the bridge and the interaction between the d orbitals of the metal centre and the bridge.

Spectroscopic and magnetic properties, and crystal structure of a dimer copper(II) complex via hydrogen bonding with a weak ferromagnetic interaction

The preparation, spectroscopic and magnetic properties, and crystal structure of [Cu(Cl)(HL)(H2O)]2·6H2O (HL stands for the monodeprotonated form of 4-methyl-amino-1,3-dimethyl-5((2′-carboxyphenyl)azo)uracil) are reported. Crystals are monoclinic, of space group P21/n, with cell constants a = 7.358(1), b = 20.542(4) and c = 13.130(3) A, β = 93.23(3)° and Z = 4. The structure was solved and refined to R = 0.059 (Rw = 0.047). The structure consists of Cl···HO hydrogen- bonded dinuclear units, which are also coupled via hydrogen bonds to form the tridimensional network. The geometry of each CuNO3Cl chromophore is almost that corresponding to an ideal square-pyramid. The magnetic results indicate a ferromagnetic ground state. The nature of the magnetic interaction is discussed on the basis of structural data.

Synthesis of polynuclear copper(II) complexes by controlling the conformation (cis or trans) of N,N′-bis(3-aminopropyl) oxamidate and the coordination mode of 2,2′-bipyrimidine

The synthesis, molecular structure and magnetic properties of three new polynuclear copper(II) complexes, [Cu( cis -oxpn)Cu(bpm)]- (ClO 4 ) 2 ·CH 3 OH ( 1 ), [Cu 2 ( trans -oxpn) (bpm) 2 ](ClO 4 ) 2 ·2H 2 O ( 2 ) and [Cu 2 ( trans -oxpn)( μ -bpm)](ClO 4 ) 2 ·2.5H 2 O ( 3 ) are reported. The compounds were prepared by controlling the conformation ( cis or trans ) of oxpn ( N , N ′-bis(3-aminopropyl)oxamidate and the coordination mode (bi- or bisbidentate) of bpm (2,2′-bipyrimidine). Complex 1 is a dinuclear complex in which the copper(II) ions are bridged by a cis -oxamidate group and where bpm acts as a bidentate terminal ligand. 2 is a trans -oxamidate-bridged dinuclear copper(II) complex with two bidentate terminal bpm molecules. In 3, a bisbidentate bpm molecule connects the dinuclear Cu 2 ( trans -oxpn) units to generate an alternating oxamidate-bpm polynuclear copper(II) chain complex. Magnetic susceptibility measurements reveal the occurrence of strong antiferromagnetic exchange couplings for the three compouns with J values of −386.0 and −328.9 cm −1 for 1 and 2 , respectively, and J = −340.0 cm −1 , with an alternation parameter α = 0.24, for 3 . Magnetic parameters are discussed on the basis of the structural results and compared with those of related complexes.

Alkali cation influence on copper cyanide solid-state architecture: two self-assembled copper(I)-sodium and copper(I)-potassium complexes showing 2D and 3D structures

Abstract Two new alternating cyano-bipyrimidine-bridged copper(I) polymers of formula [Cu2(bpm)2(CN)3Na] and [Cu(bpm)(CN)2K] (bpm=bipyrimidine) have been synthesized and their structures solved by X-ray diffraction. The structure of [Cu2(bpm)2(CN)3Na] consists of trinuclear Cu–bpm–Na–bpm–Cu units interconnected through cyanide groups to afford a 2D network, whereas that of [Cu(bpm)(CN)2K] is a 3D structure formed by interconnected cyanide-bridged copper(I)–potassium 2D honeycomb-like layers. In both structures the alkali cations play a templating role which is responsible of the final 2D and 3D network constructions.

A pro-chiral bis-imidazolyl-containing copper(II) complex as precursor of a self-assembled polymer and a heterodinuclear copper(II)–nickel(II) complex

Abstract A bis-imidazolyl tetradentate Schiff base ligand, H2L, was prepared from the condensation of imidazole-2-carbaldehyde and 1,3-diamine-2-propanol. A 1D 1H and 2D 1H COSY NMR spectroscopic study established the non-symmetry of the ligand and the existence of an asymmetric carbon atom. The ligand reacts with copper(II) perchlorate in neutral medium to yield the mononuclear complex [Cu(H2L)(H2O)](ClO4)2. As expected, X-ray crystal study confirms that the copper(II) ion occupies the inner N4 site of the non-deprotonated ligand. In basic medium the complex [Cu(H2L)(H2O)](ClO4)2 polymerises by a self-assembly reaction to [Cu(L)]n. This process is reversible and, at acid pH, the polymer structure dissociates into mononuclear units. In basic medium and in the presence of an excess of nickel(II)bishexafluoracetylacetonate, [Ni(hfa)2], a complex with two available coordination sites, it is possible to avoid the self-assembly reaction and to obtain a heterobimetallic copper(II)–nickel(II) system by the coordination of one of the imidazolate groups to the nickel(II) ion. The fact that only one of the two imidazolate groups coordinates a nickel(II) ion reveals the chemical asymmetry of the copper(II) complex.

Structural and magnetic studies of a zigzag chain copper(II) complex and a dipolar spin-coupled copper(II) dimer with the versatile ligand 5-[(2-carboxyphenyl)azo]-1,3-dimethylbarbituric acid

On treating H2L {5-[(2-carboxyphenyl)azo]-1,3-dimethylbarbituric acid} with Cu(NO3)2·3H2O in ethanol–water (4 : 1) the tetranuclear complex [{CuL(H2O)}4]1 is obtained. When 1 is dissolved in pyridine(py)–ethanol (1 : 1) the complex [{CuL(py)·3H2O}n]2 is isolated. Both complexes in pyridine solution yield [CuL(py)2]3. A magnetic study of 1 points to a ferromagnetic ground state (ST= 2). The structures of 2 and 3 have been determined by X-ray crystallographic methods. The structure of 2 consists of infinite zigzag chains running along the b axis, in which copper ions are sequentially bridged by the barbituric ring. The copper presents a distorted square-pyramidal environment. In the basal plane, four bonds are formed with the ligand and the molecule of pyridine, while the apical position is occupied by an oxygen atom belonging to the barbituric ring of an adjacent fragment; the ligand then acts in a tetradentate fashion. The copper–copper intrachain distance is 6.322(3)A. The structure of 3 consists of discrete [CuL(py)2] molecules in which the ligand acts in a tridentate fashion. The copper co-ordination is distorted square-pyramidal. The complex packs in the crystal lattice as symmetry-related pairs of molecules, with a Cu ⋯ Cu separation of 5.410(3)A. From magnetic susceptibility measurements, complex 2 is found to exhibit ferromagnetic intrachain interactions with an exchange coupling of J/2k= 1.7, whereas a Curie–Weiss law is observed for 3. Even though 3 lacks any close contact between molecules which may be regarded as bonding interactions, the polycrystalline EPR spectrum at 90 K exhibits a half-field signal, which is indicative of a spin-coupling process.

Crystal structure of a novel tertiary phosphine coordination complex: dichlorobis(tribenzylphosphine)nickel(II)

AbstractThe title compound dichlorobis(tribenzylphosphine)nickel(II), Ni[P(CH2C6H5)3]2Cl2, belongs to a type of tertiary phosphine coordination complex, M(PR3)2X2. There are two molecules in the unit cell which do not appear to interact chemically. Both molecules have a trans-square planar configuration with each nickel atom on a center of symmetry. Three benzyl groups are bonded to each phosphorus atom as rotors in a propeller, and the threefold axis is along the P—Ni bond, which has a mean length of 2.23(1) Å. Crystal data: C42H42Cl2NiP2, Triclinic, space group

Copper (II) complexes of two new oxamidate bis-tetradentate Schiff-base ligands

P\bar 1