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Two new six-coordinated high-spin Co(II) complexes have been synthesized through the reactions of Co(II) salts with dipyridylamine (dpamH) and 5-nitro-salicylaldehyde (5-NO2-saloH) or 3-methoxy-salicylaldehyde (3-OCH3-saloH) under argon atmosphere: [Co(dpamH)2(5-NO2-salo)]NO3 (1) and [Co(dpamH)2(3-OCH3-salo)]NO3·1.3 EtOH·0.4H2O (2). According to the crystal packing of compound 1, two coordination cations are linked with two nitrate anions into a cyclic dimeric arrangement via N-H···O and C-H···O hydrogen bonds. In turn, these dimers are assembled into (100) layers through π-π stacking interactions between inversion-center related pyridine rings of the dpamH ligands. The crystal packing of compound 2 reveals a 1D assembly consisting solely from the coordination cations, which is formed by π-π stacking interactions between pyridine rings of one of the dpamH along the [010] and another 1D assembly of the coordination cations and nitrate anions through the N-H···O hydrogen-bonding interactions along the [001] direction. All complexes were magnetically characterized, and a new approximation method was used to fit the magnetic susceptibility data in the whole temperature range 2-300 K on the basis of an empirical expression which allows the treatment of each cobalt(II) ion in axial symmetry as an effective spin S(eff) = 1/2. In zero-field, dynamic magnetic susceptibility measurements show slow magnetic relaxation below 5.5 K for compound 2. The slow dynamics may originate from the motion of broad domain walls and is characterized by an Arrhenius law with a single energy barrier Δr/k(B) = 55(1) K for the [10-1488 Hz] frequency range. In order to reveal the importance of the crystal packing in the SCM behavior, a gentle heating process to 180 °C was carried out to remove the solvent molecules. The system, after heating, undergoes a major but not complete collapse of the network retaining to a small percentage its SCM character.

An iron(III) complex with the hexadentate ligand 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate (1,3-pddadp) was prepared, chromatographically isolated as its isomer trans(O5O6)-Cs[Fe(1,3-pddadp)] · 2H2O, and characterized. The trans(O5O6) configuration of the iron(III) compound was found to dominate and this geometry was established by means of IR spectroscopy and Density Functional Theory (DFT). Structural data correlating the octahedral geometry of the [Fe(1,3-pddadp)]− unit and an extensive strain analysis are discussed in relation to the information obtained for similar complexes. Antibacterial activities of the free ligand and its corresponding iron(III) complex towards common Gram-negative and Gram-positive bacteria are reported as well.

Novel N-N-N-O-type of tetradentate ligands H(3)obap (H(3)obap = oxamido-N-aminopropyl-N'-benzoic acid) and H(3)maeb (H(3)maeb = malamido-N-aminoethyl-N'-benzoic acid) and the corresponding square-planar copper(H) complexes have been prepared and characterized. The obap(3)- and maeb(3)- ligands coordinate to the copper(II) ion via four ligating atoms (three deprotonated atoms: one carboxylate oxygen and two deprotonated amide nitrogens; one amine nitrogen) with in-plane square chelation. A four coordinate, square-planar geometry has been established crystallographically for the binuclear Na-2[Cu(obap)](2)center dot 2H(2)O complex. Structural data correlating the square-planar geometry of the [Cu(obap)](-) unit and an extensive strain analysis are discussed in relation to the information obtained for similar complexes. The infrared and electronic absorption spectra of the complexes are discussed in comparison to the related complexes of known geometries. Antibacterial activity of ligands and copper(H) complexes towards common Gram-negative and Gram-positive bacteria are reported as well. (c) 2005 Elsevier B.V. All rights reserved.

The preparation and resolution of the two hexadentate Co(III) complexes containing unsymmetrical edta-type ligands, [Co(ed3ap)]− (A) and [Co(u-eddadp)]− (B) (ed3ap = ethylenediamine-N,N,N′-triacetate-N′-3-propionate ion; u-eddadp = ethylenediamine-N-diacetate-N′-di-3-propionate ion) have been reexamined. The X-ray data are reported for the Λ-(−)546-trans(O)5-Li[Co(ed3ap)]·H2O for which the same (Λ) absolute configuration was predicted from the CD sign pattern of the lowest energy band. The complex crystallizes in the space group P21 (#4) of the monoclinic crystal system with a = 6.523(4), b = 15.025(7), c = 7.464(3) A, β = 105.40(4)°, and Z = 2. The conformations of the chelate rings are found to be envelope for the glycinates and skew-boat (half-chair) for the β-alaninate ring. Structural parameters and strain analysis of [Co(edta-type)]− chelates are discussed in relation to the structure of the ligand and octahedral distortion of complexes. The CD and IR (carboxylate region) spectra of complexes A and ...

The crystal structure of Krans(O6)-[Co(1,3-pddadp)] · 3H2O(1,3-pddadp = 1,3-propanediamine-N,N'-diacetate-N,N'-di-3- propionate ion) was determined by single crystal X-ray diffraction techniques. The complex anion is a trans(O6) isomer in which the cobalt(III) ion is surrounded octahedrally by the two nitrogen and four oxygen atoms of 1,3-pddadp with the two-six-membered β-alaninate chelate rings in trans positions. This result confirms the assignment made on the basis of electronic absorption, circular dichroism and NMR spectroscopy. The complex Ktrans(O6)-[Co(1,3-pddadp)]·3H2O crystallizes in the space group P2 1 c of the monoclinic crystal system with unit cell parameters a = 9.298(2), b = 11.780(4), c = 16.771(5) A , β = 90.97(2)° and Z = 4 . The structure converged to R = 0.031 for 3019 reflections. Considerations of strains favor the trans(O6) isomer of [Co(1,3-pddadp)]−.

The reactions of N,N,N′,N′-tetramethylthiuram disulfide (tmtds) with gold(III) complexes of the [Au(L)X3] type [L = N-methylimidazole (N-Melm), 2-methylbenzoxazole (2-MeBO) and 2,5-dimethylbenzoxazole (2,5-diMeBO), X = Cl, Br or I] are reported, and yielded two main types of product - [Au(Me2dtc)X2] (A) and [Au(Me2dtc)2]X (B) (Me2dtc = N,N-dimethyldithiocarbamato anion). The ratio of the product yields (B/A) depends upon the nature of the ligand (L) and halogen (X). The ratio B/A for the reaction: [Au(L)Cl3] + tmtds = A + B, increases in the sequence N-MeIm < 2- MeBO < 2,5-diMeBO, which correlates well with the level of cytotoxic activity exhibited by the [Au(L)Cl3] complexes. A and B were characterized by their i.r., u.v-vis. and 1-n.m.r. spectra. The magnetic measurements were also recorded. The data support a squareplanar geometry for gold(III) complexes with the Me2dtc ligand bonded in a bidentate fashion; a conjecture has been verified crystallographically for [Au(Me2NCS2)2]-Br·2H2O. The X-ray analysis confirmed that the complex is composed of ionic units: [Au(Me2dtc)2] + and Br− and H2O molecules. The Au—S distances are markedly similar, falling in the 2.343(4)–2.350(3) ∘A range.

The O-N-N-O-type tetradentate ligands H2S,S-eddp (H2S,S-eddp stands for S,S-ethylenediamine-N,N'-di-2-propionic acid) and H(2)edap (H(2)edap stands for ethylenediamine-N-acetic-N'-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. N2O2 ligands coordinate to the nickel(II) ion via four donor atoms (two deprotonated carboxylate atoms and two amine nitrogens) affording octahedral geometry in the case of all investigated Ni(II) complexes. A six coordinate, octahedral geometry has been verified crystallographically for the s-cis-[Ni(S,S-eddp)(H2O)(2)] complex. Structural data correlating similarly chelated Ni(II) complexes have been used to carry out an extensive configuration analysis. Molecular mechanics and Density Functional Theory (DFT) have been used to model the most stable geometric isomer, yielding, at the same time, significant structural and spectroscopic (TDDFT) data. The results from density functional studies have been compared to X-ray data. Natural Bond Orbital (NBO) and Natural Energetic Decomposition Analysis (NEDA) have been done for the [Ni(edda-type)(H2O)(2-n)] and nH(2)O fragments. Molecular orbital analysis (MPA) is given as well. The infra-red and electronic absorption spectra of the complexes are discussed in comparison to the related complexes of known geometries.

The whole set of the nickel(II) complexes with no derivatized edta-type hexadentate ligands has been investigated from their structural and electronic properties. Two more complexes have been prepared in order to complete the whole set: trans(O(5))-Mg[Ni(ed3ap)]center dot 8H(2)O and trans(O(5)O(6))-Ba[Ni(eda3p)]center dot 4H(2)O complexes. trans(O(5)) geometry has been verified crystallographicaly and trans(O(5)O(6)) geometry of the second complex has been predicted by the DFT theory and spectral analysis. Mutual dependance has been established between: the number of the five-membered carboxylate rings, octahedral/tetrahedral deviation of metal-ligand/nitrogen-neighbour-atom angles, charge-transfer energies (CTE) calculated by the Morokuma's energetic decomposition analysis and energy of the absorption bands and HOMO-LUMO gap. (C) 2009 Elsevier B.V. All rights reserved.