Ana M. García-Deibe

Complexes of 2-acetyl-γ-butyrolactone and 2-furancarbaldehyde thiosemicarbazones: antibacterial and antifungal activity.

Cobalt, nickel, copper and zinc coordination compounds of two thiosemicarbazones with general composition ML(2) (L: monodeprotonated ligand corresponding to 2-acetyl-gamma-butyrolactone thiosemicarbazone, HL(1), and 2-furancarbaldehyde thiosemicarbazone, HL(2)) and also complexes with general composition MCl(2)(HL(2)) were synthesized (except [NiCl(2)(HL(2))] and [Co(L(2))(2)]). The interaction of CuCl(2) with HL(2) gave [CuCl(HL(2))], a copper(I) complex. The ligands and metal complexes were characterized by IR, (1)H and (13)C NMR spectroscopy, and magnetic susceptibility measurements. The crystal structure of [Ni(L(2))(2)]x 2dmso was determined and a trans-square planar coordination of the two kappa(2)-N,S chelate rings forming polymeric strips through H-bonds with dmso was observed. Actually, in all the reported complexes both ligands behaved as kappa(2)-N,S chelates, except in the case of [Co(L(1))(2)] in which HL(1) is tridentate kappa(3)-N,S,O. The antimicrobial properties of all compounds were studied using a wide spectrum of bacterial and fungal strains. The copper complexes of HL(2) were the most active against all strains, including dermatophytes and phytopathogenic fungi. Most of the studied compounds, especially [Cu(L(1))(2)], presented good activity against Haemophilus influenzae, a very harmful bacterium to humans.

Dinuclear nickel complexes with a Ni2O2 core : a structural and magnetic study

The acetylacetonate complexes [Ni(2)L(1)(acac)(MeOH)] x H(2)O, 1 x H(2)O and [Ni(2)L(3)(acac)(MeOH)] x 1.5H(2)O, 2 x 1.5H(2)O (H(3)L(1) = (2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine and H(3)L(3) = (2-(5-bromo-2-hydroxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) were prepared and fully characterised. Their crystal structures show that they are dinuclear complexes, extended into chains by hydrogen bond interactions. These compounds were used as starting materials for the isolation of the corresponding [Ni(2)HL(x)(o-O(2)CC(6)H(4)CO(2))(H(2)O)] x n MeOH and [Ni(2)HL(x)(O(2)CCH(2)CO(2))(H(2)O)]x nH(2)O dicarboxylate complexes (x = 1, 3; n = 1-3). The crystal structures of [Ni(2)HL(1)(o-O(2)CC(6)H(4)CO(2))(H(2)O)] x MeOH, 3 x MeOH, [Ni(2)HL(3)(o-O(2)CC(6)H(4)CO(2))(H(2)O)] x 3 MeOH, 4 x 3 MeOH and [Ni(2)HL(1)(O(2)CCH(2)CO(2))(H(2)O)] x 2.5H(2)O x 0.25 MeOH x MeCN, 5 x 2.5H(2)O x 0.25 MeOH x MeCN, were solved. Complexes 3-5 show dinuclear [Ni(2)HL(x)(dicarboxylate)(H(2)O)] units, expanded through hydrogen bonds that involve carboxylate and water ligands, as well as solvate molecules. The variable temperature magnetic susceptibilities of all the complexes show an intramolecular ferromagnetic coupling between the Ni(II) ions, which is attempted to be rationalized by comparison with previous results and in the light of molecular orbital treatment. Magnetisation measurements are in accord with a S = 2 ground state in all cases.

A direct route to obtain manganese(III) complexes with a new class of asymmetrical Schiff base ligands

A new class of asymmetrically substituted Schiff base ligands has been synthesised incorporating hard amido donor atoms. The single crystal X-ray structure of one of these ligands, H3-amsal, has been determined [H3-amsal=3-aza-4-(2-hydroxyphenyl)-N-(2-hydroxyphenyl)but-3-enamide]. The structure reveals the ligand to be suitable for use as an equatorially co-ordinating ligand in octahedral complexes. A new route to obtaining manganese(III) complexes of these ligands, with high yield and purity, has been designed. Complexes of the form MnIII(amsal-R)(H2O)n (n=1–4) have been prepared by the electrochemical oxidation of a manganese anode in an acetonitrile solution of the ligands. The compounds have been characterised by elemental analyses, IR and 1H NMR spectroscopies, FAB mass spectrometry, magnetic measurements, ΛM and cyclic voltammetry.

Zinc and cadmium complexes with an achiral symmetric helicand. Crystal structure of an enantiomerically pure Λ-Zn(II) monohelicate

Zn(II) and Cd(II) complexes with an N-tosyl substituted N4-donor Schiff base, containing a 2-propanol residue as spacer, have been prepared. The X-ray crystal structure of the monohelicate Λ-Zn(OHPTs)·H2O [H2OHPTs: N,N′-bis(2-tosylaminobenzylidene)-1,3-diamino-2-propanol] has been solved. The Zn(II) ion assumes a distorted tetrahedral coordination geometry, involving the four donor N atoms of the bisdeprotonated ligand. Strong (O–H⋯O) hydrogen bonds between neighbouring complex and lattice water molecules lead to intricate intermolecular interactions that seem to drive the crystal packing. This Zn(II) complex shows an intense blue fluorescence in solution (λ = 430 nm, ϕ = 0.14), which is also observed in the solid state (λ = 490 nm). Cd(OHPTs)·4H2O, although at a lower level (ϕ = 0.08), is also luminescent (λ = 430 nm) in acetonitrile solution.

Dinuclear Co(III)/Co(III) and Co(II)/Co(III) mixed-valent complexes: synthetic control of the cobalt oxidation level

The reactivity of cobalt(II) salts towards H(3)L (2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) was studied in different reaction conditions. Accordingly, the interaction of cobalt(II) acetate with H(3)L in methanol gives rise to the discrete complex [Co(III)(2)L(OAc)(2)(OMe)]*1.5H(2)O.MeOH, 1. Reaction of cobalt(II) acetylacetonate with H(3)L in the presence of dicarboxylic acids was also investigated. Thus, when cobalt(II) acetylacetonate and H(3)L are mixed with terephthalic or malonic acid in 4 : 2 : 1 molar ratios, the mixed valent [Co(II/III)(2)L(acac)(p-O(2)CC(6)H(4)CO(2)H)][Co(II/III)(2)L(acac)(OH)]*2H(2)O*2MeOH, 2 and [Co(II/III)(2)L(acac)(O(2)CCH(2)CO(2)H)][Co(II/III)(2)L(acac)(OH)]*7H(2)O, complexes are isolated. Decreasing the pH of the medium, by addition of a second mol of dicarboxylic acid, leads to [Co(II/III)(2)L(O(2)CCH(2)CO(2))(MeOH)]*2MeOH, 4, while the reaction with terephthalic acid does not proceed. 1, 2 and 4 were crystallographically characterised and all the complexes are dinuclear, with hydrogen bonds that expand the initial nodes. The magnetic characterisation, as well as the NMR spectroscopy, indicates a diamagnetic nature for 1, in agreement with the presence of Co(III), showing the aerial oxidation suffered by the cobalt(II) ions. Nevertheless, are paramagnetic. Temperature variable magnetic measurements were recorded for the crystallographically characterised complexes 2 and 4 and these studies confirm the mixed valence Co(II)/Co(III) nature of the compounds. The best fits of the magnetic data give an axial distortion parameter Delta = 628.7 cm(-1) for 2 and 698.8 cm(-1) for 4, and spin-orbit coupling constant lambda = -117.8 cm(-1) for 2 and -107.0 cm(-1) for 4. Therefore, this study shows that the oxidation degree of the initial cobalt(ii) salt by atmospheric oxygen can be controlled according to the pH of the medium.

The diversity observed in manganese(III) complexes of tetradentate Schiff base ligands: An assessment of structural trends

Abstract A series of manganese(III) complexes of aryl substituted N 2 O 2 donor set Schiff base ligands has been prepared by the aerial oxidation of manganese(II) precursors. The resultants complexes of stoichiometry [MnL]C1O 4 · n H 2 O (where n = 1–3) have been thoroughly characterised by elemental analyses, infrared spectroscopy, fast atom bombardment (FAB) mass spectrometry, magnetic susceptibility measurements and paramagnetic 1 H NMR. The crystal structure of [MnL 7 (H 2 O) 2 ]ClO 4 ·H 4 O, 1 , shows it to consist of a polymeric array of roughly octahedtal [MnL 7 (H 2 O) 2 ] + cations linked via an intricate network of hydrogen bonds between the perchlorate counterion and the lattice water molecule. This hydrogen bonding is further enhanced by π-π stabilisation between the aryl rings of the Schiff base ligands. An attempt is made to rationalise the structural chemistry observed by us for complexes of this type.

New Helical Complexes with a Bis(bidentate) Schiff Base Ligand Containing a Flexible Spacer

Neutral complexes with the general empirical formula M(PTs) [M: Mn, Fe, Co, Cu, Zn, and Cd; H2PTs: N,N′-bis(2-tosylaminobenzylidene)-1,3-diaminopropane] were obtained by means of an electrochemical procedure. All complexes were characterised by elemental analyses, mass spectrometry, IR and 1H NMR spectroscopy, and magnetic measurements, where appropriate. Recrystallisation of the cobalt, copper, and zinc complexes yielded single crystals of [Co(PTs)] (1), [Cu(PTs)]·1.5CH3CN (2) and [Zn(PTs)]2·1.5H2O·CH3CN (3). Their X-ray characterisation shows that 1 and 2 are mononuclear tetrahedral single-stranded helical complexes in the solid state, while 3 is a double-helical compound containing a major and a minor groove, with the Schiff base acting as a bis(bidentate) N4 donor.

Insights into the absorption of carbon dioxide by zinc substrates: isolation and reactivity of di- and tetranuclear zinc complexes

The heptadentate Schiff base H(3)L can react with zinc acetate to form the discrete dinuclear complex Zn(2)L(OAc)(H(2)O), 1.H(2)O. The reaction of 1.H(2)O with NMe(4)OH.5H(2)O both in air and under an argon stream has been investigated. On one hand, this reaction in air yields the tetranuclear complex (Zn(2)L)(2)(CO(3))(H(2)O)(6), 2.5H(2)O, by spontaneous absorption of adventitious carbon dioxide. This process can be reverted in an acetic acid medium, whereas the treatment of 2.5H(2)O with methanoic acid yields crystals of [Zn(2)L(HCOO)].0.5MeCN.1.25MeOH.2H(2)O, 3.0.5MeCN.1.25MeOH.2H(2)O. On the other hand, the interaction under an argon atmosphere of 1.H(2)O with NMe(4)OH.5H(2)O in methanol allows the isolation of the dinuclear complex Zn(2)L(OMe)(H(2)O)(4), 4.4H(2)O. Recrystallisations of 1.H(2)O, 2.5H(2)O and 4.4H(2)O, in different solvents, yielded single crystals of 1.MeCN.2.5H(2)O, 2.4MeOH and 4.3MeOH.H(2)O, respectively. The crystal structure of 2.4MeOH can be understood as resulting from an unusual asymmetric tetranuclear self-assembly from two dinuclear units, and shows three different geometries around the four zinc atoms.

Metallo-helicates with an N4-Schiff base containing a flexible alkyl spacer

Neutral Mn(II), Fe(II) and Co(II) complexes with an N -tosyl substituted N4-Schiff base containing a tetra-methylene spacer have been prepared. The X-ray crystal structures of ligand H2BTs [N ,N ?-bis(2-tosylaminobenzylidene)-1,4-diaminobutane] and helical Co(BTs)/0.5H2BTs have been solved. The Co(II) ion assumes a distorted tetrahedral coordination geometry, involving the four donor N -atoms of the dianionic ligand. Additionally, secondary interactions between the metal centre and one of the O -atoms of each tosyl group were detected. These groups are differently conformed, so that the ligand behaves as a non-symmetric helicand. # 2002 Elsevier Science B.V. All rights reserved.

Discovering the Complex Chemistry of a Simple NiII/H3L System: Magnetostructural Characterization and DFT Calculations of Di- and Polynuclear Nickel(II) Compounds

The simple nickel(II) acetate/H(3)L system (H(3)L = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) presents an unusually complicated reactivity scheme, which strongly depends on the Ni(OAc)(2)/H(3)L molar ratio and on the pH of the medium. Thus, in addition to the formerly reported compounds [Ni(2)L(OAc)(H(2)O)(2)][Ni(2)L(OAc)(H(2)O)(HOAc)].3.25H(2)O, 1.3.25H(2)O; [{Ni(3)L(OAc)(OH)(H(2)O)(MeOH)(2)}(CO(3)){Ni(2)L(OAc)(MeOH)(2)}].2.7H(2)O.1.5MeOH, 2.2.7H(2)O.1.5MeOH; and [Ni(3)L(OAc)(2)(OH)(H(2)O)(MeOH)(2)].3H(2)O.0.5MeOH, 3.3H(2)O.0.5MeOH, this system can also yield some other complexes as [Ni(2)L(o-O-C(6)H(4)-CHO)(H(2)O)].1.75H(2)O, 4.1.75H(2)O; [Ni(2)L(OH)(H(2)O)(MeOH)].3H(2)O.1.5MeOH, 5.3H(2)O.1.5MeOH; [Ni(2)L(OAc)(MeOH)(2)].H(2)O.3MeOH, 6.H(2)O.3MeOH; and [{Ni(2)L(MeOH)}(CO(3)){Ni(2)L(MeOH)(2)}].4.75H(2)O.2MeOH, 7.4.75H(2)O.2MeOH. A detailed study of the reaction scheme that allows obtaining all of these complexes is presented herein, as well as the structural characterization of the novel compounds 4.1.75H(2)O to 7.4.75H(2)O.2MeOH. X-ray analyses show that all of them present stereoisomery in the solid state. In this way, 6.H(2)O.3MeOH appears particularly interesting, as its molecular and supramolecular chirality is only controlled by hydrogen bonds. Magnetic studies of 5.3H(2)O to 7.4.75H(2)O.2MeOH are also discussed, and the complicated magnetic superexchange pathway shown by 7.4.75H(2)O.2MeOH is analyzed in light of DFT calculations.