Oscar V. Quinzani

Structural and spectroscopic characterization of two new Cd(II) complexes: bis(thiosaccharinato)bis(imidazole) cadmium(II) and tris(thiosaccharinato)aquacadmate(II)

Abstract The crystal structures of [Cd(tsac)2(im)2] (1) (tsac=anion of thiosaccharine; im=imidazole) and of (Him)[Cd(tsac)3(H2O)] (2) (Him=imidazolium cation) have been determined at 120 K by single crystal X-ray diffractometry. Complex 1 crystallises in the monoclinic space group P21/a with Z=4 whereas compound 2 is triclinic, space group P(−1) and Z=2. In both compounds, Cd(II) is in a distorted tetrahedral environment. In the neutral complex 1 the metal is coordinated to the S-atom of the two thiosaccharinato ligands and to the N-atom of the imidazole molecules. In the anionic complex 2, Cd(II) is coordinated to three thiosaccharinato S-atoms and to the O-atom of the water molecule. The FTIR spectra of both compounds were also recorded and briefly discussed.

Significant anti-inflammatory properties of a copper(II) fenoprofenate complex compared with its parent drug: Physical and chemical characterization of the complex

The synthesis, physicochemical characterization, anti-inflammatory properties and catecholase mimetic activity of the dinuclear complex of copper(II) with the non-steroidal anti-inflammatory drug Fenoprofen [2-(3-phenoxyphenyl)propionic acid] with formula [Cu2(fen)4(dmf)2] (fen = fenoprofenate anion, dmf = N,N-dimethylformamide) have been investigated. Results of spectroscopic analysis (FTIR and EPR) as well as thermogravimetric and differential thermal analysis data obtained for the solid complex are in good agreement with its dinuclear structure. Electronic spectra of the product are also reported and discussed. The complex was tested for anti-inflammatory properties in comparison to the parent drug, Fenoprofen calcium salt. Oral administration of the dinuclear compound inhibited development of carrageenan-induced oedema in mice; this inhibition was higher than that observed for the parent drug. The kinetic study of the catecholase mimetic activity was carried out spectrophotometrically by monitoring the oxidative transformation of 3,5-di-tert-butylcatechol into the corresponding light-absorbing o-quinone. Kinetic parameters were determined employing the Michaelis-Menten model, showing that the new complex presents catechol oxidase mimetic activity.

Pd(thiosaccharinato)2·H2O, the first thiosaccharinato complex of a platinum-group metal

A Pd(II) complex of the thiosaccharinato (tsac) anion, of stoichiometry Pd(tsac)2·H2O was prepared by interaction of Na2PdCl4 with thiosaccharin in methanol and characterized by infrared and 1H and 13C NMR spectroscopy. These spectral studies confirmed interaction of the metal center with the thiosaccharinate acting as a bidentate ligand through its thiol group and the N-atom. NMR measurements also confirmed that in solution thiosaccharin is mainly present in its thiolate tautomeric form.

Reversible S−S Bond Breaking and Bond Formation in Disulfide-Containing Dinuclear Complexes of MnI

Disulfide-containing compounds are of considerable biological[1] and technological relevance,[2] and the mechanisms by which the sulfurÿsulfur bond in these compounds can be reversibly broken and formed has attracted a great deal of interest.[3] We have recently reported that nucleophilic degradation of cyclooctasulfur by the diphosphanylmethanide complex of manganese(i) [Mn(CO)4{(PPh2)2CH}] allows the formation of the hexasulfur-bridged bis(diphosphanylmethanide) dimetallic derivative [(CO)4Mn{(PPh2)2CÿS6ÿC(PPh2)2}Mn(CO)4]. In this complex the polysulfur chain can be progressively shortened by treatment with PPh3 leading finally to the disulfide compound 1, which does not undergo further sulfur extrusion processes.[5] We have now explored the chemistry of this disulfide derivative with regard to the controlled scission and formation of the sulfurÿsulfur bond, promoted either by redox processes or by combined redox and acid-base treatments. This has led to a number of scarce functionalities such as diphosphanylthioketone, sulfenyl iodide, and thioxophosphorane ylide, as parts of the corresponding carbonyl complex of manganese(i).

New approach to the chemistry of polysulfides using diphosphanylmethanide complexes of manganese(I).

The study of the nucleophilic degradation of S8 by the methanide complex [Mn(CO)4[(PPh2)2CH]] (2) has led to the preparation of a unique class of polysulfide derivatives of formula [(CO)4Mn[(PPh2)2C-Sn-C(PPh2)2]-Mn(CO)4]. The structures of 3 (n = 6), 4 (n = 2), and 7 (n = 1) have been determined by X-ray crystallography, whereas those polysulfides with the sulfur chains S7, S5, S4, and S3 have been detected by spectroscopic methods. The polysulfides with n > 2 lose sulfur spontaneously, a process that can be accelerated by treatment with PPh3 or Na/Hg. Complexes 3, 4, and 7 were protonated at the two methanide carbon atoms to give the cationic dinuclear derivatives [(CO)4Mn[(PPh2)2C(H)-Sn-C(H)-(PPh2)2]Mn(CO)4]2+ (8, n=6; 9, n=2; 10, n = 1). The 1H NMR spectrum of 9 suggests the existence of intramolecular C-H...S interactions, in agreement with the X-ray structural determination of this complex. By treatment of 4 and 7 with one equivalent of HBF4 it is possible to selectively protonate just one methanide carbon atom, which allows the isolation of the mixed cationic derivatives R(CO)4Mn[(PPh2)2C(H)-Sn-C(PPh2)2]Mn(CO)4]+ (11, n = 2; 6, n = 1). Additionally, heterometallic complexes containing a bridging disulfide unit, of general formula [(CO)4Mn[(PPh2)2C(AuPPh3)S-SC-(AuPPh3)(PPh2)2]Mn(CO)4]2+ (12) and [(CO)4Mn[(PPh2)2C(H)S-SC(AuPPh3)-(PPh2)2]Mn(CO)4]+ (13), were prepared by reaction of 4 and 11, respectively, with [AuCl(PPh3)] in the presence of TlPF6.

Poly[(μ3-1,1-dioxo-1,2-benzoisothiazole-3-thiolato-κ3N:S3:S3)silver(I)]

The centrosymmetric title compound, [Ag(C(7)H(4)NO(2)S(2))]n, consists of dinuclear units in which two thiosaccharinate anions each bridge two Ag atoms via an endocyclic N atom and an exocyclic S atom across a crystallographic centre of inversion midway between the Ag atoms. The dimeric units are connected via Ag-S(exo) interactions to create two-dimensional networks. The thiosaccharinate anions bridge in a mu3-S:S:N manner. The Ag...Ag distance can be considered a strong argentophilic interaction.

Dinuclear copper(II) complexes of Fenoprofen: synthesis, spectroscopic, thermal, and SOD-mimic activity studies

Three dinuclear copper(II) complexes with the anti-inflammatory drug Fenoprofen [Hfen, 2-(3-phenoxyphenyl)propionic acid] and nitrogen donors of general formula [Cu2(fen)4(L)] n were prepared from [Cu2(fen)4(dmf)2]·2H2O (1) [dmf = N,N′-dimethylformamide; L = 4,4′-bipyridine (2), pyrazine (3), and 2,5-dimethylpyrazine (4)]. The new complexes were characterized by chemical analysis, spectroscopic, and thermogravimetric techniques. Antioxidant properties of 1–4 were evaluated for superoxide-dismutase-mimic activity employing the XTT method. Complex 2 presented the highest antioxidant activity (IC50 = 0.260 µmol L−1). Anti-inflammatory properties of 2 were evaluated employing carrageenan-induced paw edema in mice, revealing that the Fenoprofen–copper(II) complex containing 4,4′-bipyridine does not present enhanced anti-inflammatory activity compared to the uncomplexed parent drug Fenoprofen calcium salt.

Tetra­kis[μ-2-(3-phenoxy­phen­yl)propionato-κ2O:O′]bis­[(dimethyl­formamide-κO)copper(II)]

The title compound, [Cu2(C15H13O3)4(C3H7NO)2], is formed by the chelate coordination of four racemic fenoprofenate (fenoprofenate is 2,3-phenoxyphenyl propionate) anions and two dimethylformamide molecules to two copper(II) ions, building a paddle-wheel dinuclear molecule. The distorted square-pyramidal coordination of each CuII atom is made up of four O atoms of the four fenoprofenate units and another O atom from a dimethylformamide molecule. The two enantiomeric forms of the fenoprofenate anions are present in the complex, in an optically inactive centrosymmetric arrangement.

THERMAL BEHAVIOUR OF COPPER(II) COMPLEXES OF HALOASPIRINATES

Complexes of Cu(II) with substituted o-acetoxy benzoic acids (5-haloaspirines, X-asp) with and without pyridine (py), of composition [Cu2(X-asp)4] and [Cu(X-asp)2(py)2 ] have been synthesized and characterized. Electronic and vibrational spectroscopic data of these complexes are reported. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. In all complexes, the haloaspirinate ligands decompose in two or three steps, starting with the break up of the coordinated acetoxy groups. CuO is obtained as the final pyrolysis residue in all cases.