Febee R. Louka

Synthesis, structure and magnetic characterization of dinuclear copper( ii ) complexes bridged by bicompartmental phenolate

The reaction of Cu(II) salts with the bicompartmental 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenol (LCl-OH) ligand afforded four new dinuclear bridged phenoxido Cu(II) complexes. Three doubly bridged complexes namely [Cu2(μ-LCl-O)(μ-X)](ClO4)2 (1: X = OH−, 3: X = O2P(OC6H5)2−) and 2: [Cu2(μ-LCl-O)(μ-pz)(ClO4)]ClO4 (2) where pz = pyrazolyl anion, and one singly bridged-phenoxido, [Cu2(μ-LCl-O)(dca)2]PF6·2CH3CN (4·2CH3CN) (dca = dicyanamide anion). A complex similar to 4 was also obtained with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol (LMe-OH), [Cu2(μ-LMe-O)(dca)2]PF6·2CH3CN (5·2CH3CN) where in both cases dca are acting as terminal monodentate ligands. The complexes were structurally characterized by various spectroscopic techniques (IR, UV-VIS and ESI-MS) and by single crystal crystallography. Magnetic susceptibility measurements at variable temperature revealed strong to very strong antiferromagnetic coupling (AF) in the doubly bridged complexes 1–3 and very weak AF interaction in the dicyanamido compounds 4 and 5. The DFT calculations for the coupling constants, J were in agreement with the experimentally observed behavior. The trend in magnetic properties was attributed to the strength of overlap between the orbitals (dx2−y2/dx2−y2vs. dz2/dx2−y2vs. dz2/dz2) resulting from trigonal bipyramidal (TBP) or square pyramidal (SP) geometries.

Magneto-structural properties of carbonato-bridged copper(II) complexes: fixation of atmospheric CO2

Two carbonato-bridged Cu(II) complexes, [Cu3(dmMePEA)3(μ3-CO3)(ClO4)3]ClO4 (1) and [Cu2(iptren)2(μ2-CO3)](ClO4)2·H2O (2), (dmMePEA = N-methyl(2-(2-pyridyl)ethyl)-(4-methoxy-3,5-dimethyl-2-pyridylmethyl)amine, iptren = tris[2-(isopropylamino)ethyl]amine) were synthesized through the atmospheric fixation of CO2. The complexes were structurally and magnetically characterized. Tris(bidentate) and bis(monodentate) carbonato-bridge bonding modes were found in the two complexes. Variable temperature magnetic susceptibility (2–300 K) revealed weak bulk ferromagnetic coupling in complex 1 (J = 1.1 cm−1) and very strong antiferromagnetic coupling in 2 (J = −167.7 cm−1). The magnetic properties of the two complexes are discussed as a function of their structure parameters and in relation to those of other related complexes of similar carbonato-bridging bonding modes.

Polynuclear and polymeric squarato-bridged coordination compounds

The coordination properties of 3,4-dihydroxycyclobut-3-ene-1,2-dionate, C4O42− (squarate dianion) ligand, in relation to its ability to form different bonding bridging modes with metal ions are explored. These bonding modes led to the formation of a wide range of polynuclear and polymeric coordination compounds. The magnetic properties of the structurally characterized bridged-squarato compounds with Cu(II) and Ni(II) are reported as a function of the structural parameters of the complexes.

Cobalt(III) complexes of tripod amines. Kinetics of aquation of dichloro(N-(2-aminoethyl)-N,N-bis- (3-aminopropyl)amine)cobalt(III) ion

A new series of six-coordinate cobalt(III) complexes containing tripod tetradentate-N donors (N4), [Co(abap)Cl2]ClO4 · H2O, [Co(abap)(H2O)Cl]Cl(ClO4) and [Co(N4)X2]ClO4 (N4 = abap, X = N3, NO2; N4 = TPA, X = Cl, NO2) where abap = N-(2-aminoethyl)-N,N-bis(3-aminopropyl)amine and TPA = tris(2-pyridylmethyl)amine were synthesized and characterized by elemental analyses, UV–Vis, and IR. The kinetics of the primary aquation of the complex ion [Co(abap)Cl2]+ to [Co(abap)(H2O)Cl]2+ was followed spectrophotometrically in 50/50 (v/v) CH3CN/aqueous HClO4 (16–37°C and I = 0.50 M NaClO4). Rate constants (k 1) evaluated under pseudo first-order conditions, were found to be independent of the [H3O+] over the range of 0.10–0.50 M HClO4 and of the initial complex concentration. At 25°C, the k 1 value was found to be 1.65 × 10−3 s−1 indicating that this process is, unexpectedly, slightly slower than the corresponding reaction in [Co(tren)Cl2]+ (k 1 = 2.96 × 10−3 s−1). The activation parameters were calculated (  = 61.9 ± 1.8 kJ mol−1 and  = −91.0 ± 6.1 J K−1mol−1), and the results are discussed in relation to other closely related systems with a dissociative I d mechanism.

Copper(II) complexes based on tripodal pyrazolyl amines: Synthesis, structure, magnetic properties and anticancer activity

The Cu(II) complexes [Cu(bpdmpz)Cl]ClO4 (1), [Cu(bdmpzp)Cl]ClO4 (2-ClO4), [Cu(bdmpzp)Cl]PF6 (2-PF6) and [Cu(tdmpza)Cl]ClO4 (3), bpdmpzp=[bis[((2-pyridylmethyl)-di(3,5-dimethyl-1H-pyrazolyl)methyl)]amine, bdmpzp=[bis((di(3,5-dimethyl-1H-pyrazolyl)methyl)-(2-pyridylmethyl)]amine and tdmpza=tris[di(3,5-dimethyl-1H-pyrazolyl)-methyl)]amine were synthesized and characterized by elemental analysis, magnetic and conductivity measurements, electrospray-ionization mass spectrometry, infrared and electronic spectroscopy, and X-ray crystallography. The magnetic properties of the complexes, measured at variable temperature, revealed weak antiferromagnetic intermolecular interactions. The cytotoxicity of the complexes 1, 2-ClO4, 3, and 4 ([Cu(bedmpzp)Cl]PF6, where bedmpzp=[bis(3,5-dimethyl-1H-pyrazol-1-yl-1-ethyl)-(2-pyridylmethyl)]amine), was investigated against four human cancer cell lines: A2780 (ovarian), A2780R (cisplatin-resistant variant), HOS (aggressive bone tumors), CaCo2 (epithelial colorectal adenocarcinoma) and on healthy human hepatocytes. The complex 4 was the most cytotoxic one, with IC50=1.4μM (A2780), 8.3μM (A2780R), 4.7μM (HOS) and 10.8μM (CaCo2). The mass spectrometry-based interaction studies, involving selected sulfur-containing biomolecules and small model proteins, revealed pro-oxidant effects of complexes 1 and 4 and differences in stability of both complexes in the mixtures containing the model protein cytochrome c after 24h incubation, complex 1 formed 1:1 adduct, the formation of which was accompanied by the loss of one dimethylpyrazole pendant arm from the bpdmpz ligand, while the complex 4 composition remained intact and the complex formed both 1:1 and 1:2 adducts (cytochrome c vs. Cu(II)-complex).

Croconato-bridged copper(II) complexes: synthesis, structure and magnetic characterization

Three croconato-bridged Cu(II) complexes were synthesized and structurally characterized including dinuclear [Cu2(Et4dien)2(μ1,2,3,4-C5O5)](ClO4)2·3H2O (1) and [Cu2(pmap)2(μ1,2,3,4-C5O5)](ClO4)2·2H2O (2) and the 1D coordination polymer {[Cu(dmpzp)(μ1,2,3,4-C5O5)]·H2O}n (3), where Et4dien = N,N′,N′′,N′′-tetraethylethylenetriamine, pmap = bis(2-(2-pyridyl)ethyl)-(2-pyridylmethyl)amine and dmpzp = 1-(2-methylpyridyl)-3,5-dimethyl-1-H-pyrazole. The synthesized complexes were further characterized by a single crystal X-ray analysis which revealed the bis-bidentate chelating nature of the μ1,2,3,4-croconato ligand with the intra-dimer Cu⋯Cu bond distances ranging from 6.79 to 7.69 A across the bridged croconate. The magnetic susceptibility measurements at varying temperatures (1.9–300 K) showed that the complexes exhibit a weak antiferromagnetic (AF) coupling with J values = −2.67 cm−1 for 1 and 2, and −4.05 cm−1 for 3. The weak AF coupling was also predicted based on the DFT calculations. The magnetic properties of the complexes are discussed in light of their structures and compared with the previously reported croconato-bridged Cu(II) complexes.