Aglaia Koutsodimou

Synthesis and spectroscopic studies of diorganotin derivatives with tolfenamic acid. Crystal and molecular structure of the first complex of tolfenamic acid, 1,2:3,4-di-μ2-2-[(3-chloro-2-methylphenyl)amino]-benzoato-O,O-1,3-bis-2-[(3-chloro-2-methylphenyl)amino]benzoato-O-1,2,4:2,3,4-di-μ3-oxo-tetrakis[di-n-butyltin(IV)]

Abstract The complexes [Me2LSnOSnLMe2]2 (1) [Bu2LSnOSnLBu2]2 (2) and Bu2SnL2.H2O (3), where HL is 2-[bis(3-chloro-2-methylphenyl)amino]benzoic acid (tolfenamic acid), have been prepared and characterized structurally by means of 19Sn Mossbauer, vibrational and 1H- and 13C-NMR spectroscopies. The crystal structure of complex 2 has been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxanes of planar ladder arrangement with distorted trigonal-bipyramidal geometry about the five-coordinated tin centers. The structure, which has twofold symmetry, features a central Sn2O2 unit with two additional tin atoms linked at O. Pairs of tin atoms are bridged by bidentate carboxylate ligands and the external tin atoms have their coordination geometry completed by a monodentate carboxylate ligand. The tin atom geometries are similar and are based on a trigonal bipyramidal arrangement. Significant π→π stacking, C–H–π interactions and intrarmolecular hydrogen bonds stabilize this structure. The polar imino hydrogen atom on N(1) and N(2) participate in a bifurcate intramolecular hydrogen bond. In this case complex 2 is self-assembled via C–H–π and π→π stacking interactions. Tin-119 Mossbauer, vibrational and NMR data are discussed in terms of the crystal structure and the proposed structures for 1 and 3. From the variable-temperature Mossbauer effect, the Debye temperatures for 1–3 were determined.

Organotin-Drug Interactions. Organotin Adducts of Tenoxicam: Synthesis and Characterization of the First Organotin Complex of Tenoxicam

The synthesis and spectral characterization of the novel organotin complexes [SnBu2(ten)] (1) and [SnBu2(Hten)2] (2) of the potent and widely used anti-inflammatory drug tenoxicam (H2ten) are reported. A crystal-structure determination of 1 showed that, in this complex, the ligand is doubly deprotonated at the hydroxy O-atom and the amide N-atom and is coordinated to the SnBu2 fragment via four- and six-membered chelate rings. An extended network of Sn−O−Sn, C−H⋅⋅⋅O and C−H⋅⋅⋅π contacts lead to aggregation and a supramolecular assembly. Potentiometric titrations in nonaqueous solutions support the ionization of the drug by removal of the second H-atom, the amide H-atom, in the presence of the diorganotin(IV) fragment. The Ka values of the poorly H2O-soluble drug tenoxicam were obtained spectrophotometrically in aqueous solutions of constant ionic strength.

Transition metal orotic acid complexes

Complexes of orotic acid with transition metals (Cu2+, Mn2+, VO2+, Zn2+, Hg2+, Cd2+, Fe3+, Cr3+, and Ag+) have been prepared and characterized by elemental, conductivity, magnetic measurements, i.r., n.m.r. and diffuse reflectance spectra. The ligand, in its monoanion form, coordinates through the carboxylic group to the metal. The Co2+ complex was also isolated under alkaline conditions and studied.

Organotin(IV) complexes with 2-(2′-pyridyl)quinoxaline (L): The crystal structure of the [SnEt2Cl2L]·0.5 benzene

Abstract Complexes of 2-(2′-pyridyl)quinoxaline (L) with R2SnCl2 (R=Me, Et, Bun) have been synthesized and characterized using IR, far-IR, 119Sn Mossbauer, 1H and 13C spectroscopies. The X-ray crystal structure of Et2SnCl2L shows a bidentate chelating behaviour of L, which is observed in all the diorganotin compounds presented. Interaction of the ligand L with SnCl4 resulted in the formation of a salt with the formula [(LH)2]2+[SnCl6]2−. Solution studies of the complexes R2SnCl2L (R=Me, Et, Bun) revealed partial dissociation of the ligand in chloroform.

Mixed ligand Ru(II) complexes with 2,2′-bipyridine and 2-(2′-pyridyl)quinoxaline

Abstract The synthesis and the physical properties of a new series of Ru(II) mixed ligand tris chelate complexes of the type [LxRu (bpy)3−x], where L=2-(2′-pyridyl) quinoxaline and bpy=2,2′-bipyridine, are reported. The complexes were fully characterized by NMR spectroscopic techniques, Electrospray Mass Spectroscopy, UV–visible spectra and elemental analyses. The complex [RuL3](PF6)2 probably has the mer conformation due to the bulky shape of the L on the side of quinoxaline. The complex [RuL2(bpy)](PF6)2 was isolated as a mixture of all three possible geometric isomers, while the [RuL(bpy)2](PF6)2 in only one isomer as theoretically expected. Photoinduced dissociation of one molecule of the ligand L from the complex [RuL3](PF6)2 upon exposure to room light has been studied by 1H NMR and UV–vis Spectroscopies.

Synthesis and characterisation of two new lanthanide sandwich-type heteropolyoxometalates

The sodium and cesium salts of two new heteropolyoxometalate complexes [{Ln3O3(OH2)2}(PW9O34)2] 15� were synthesized and studied using spectroscopy and cyclic voltammetry. The stoichiometry of the trilacunary Keggin 9-tungstophosphate reaction with Ln(III) ions was determined with the aid of conductometric titrations of aqueous solutions. Ion-exchange as well as ES-MS experiments provided evidence for covalent, inner-sphere bonding of lanthanide cations to the trilacunary a-[PW9O34] 9� heteropolyanion. Cyclic voltammograms of [{Ln3O3(OH2)2}(PW9O34)2] 15� exhibited two pairs of reduction/oxidation waves with negative half-wave potential (E1/2) values. These waves were attributed to redox processes corresponding to the polyoxotungstate framework. The redox processes of the Ce derivativ er evealed the presence of two types of cerium ions. # 2003 Elsevier Ltd. All rights reserved.

Synthesis and characterization of K6[Ti(H2O)P2MoW16O61]·17H2O, a Ti(IV) derivative of monolacunary Wells-Dawson 16-tungsto-molybdo-2-phosphate

Abstract Monolacunary Wells-Dawson 16-tungsto-molybdo-phosphate [P2MoW16O61]10− reacts with [Ti(H2O)6]4+ in aqueous solution to give the [Ti(H2O)P2MoW16O61]6− complex, isolated as the potassium salt. Optimal synthesis conditions were established by spectrophotometric and conductometric studies. The molecular formula of the complex was determined by elemental analysis, thermogravimetric analysis and basicity titration. The Ti(IV) complex was further characterized by UV, FTIR, Raman and 31P NMR spectroscopies as well as cyclic voltammetry. Powder X-ray diffraction was used to obtain the lattice parameters for both ligand and complex. A modified Wells-Dawson structure for the new Ti(IV) polyoxometalate complex was inferred from the results.

Synthesis and Characterization of New Rare‐Earth Sandwich‐Type Tungstoarsenates

Two new sandwich‐type tungstoarsenate complexes [{Ln3O3(OH2)2}(AsW9O34)2]15− (Ln=La, Ce) were synthesized and studied using spectroscopy and cyclic voltammetry. Ion‐exchange experiments provided evidence for covalent, inner‐sphere bonding of the rare‐earth cations to the trilacunary [AsW9O34]9− polyoxometalate. Cyclic voltammograms of [{Ln3O3(OH2)2}(AsW9O34)2]15− exhibited two pairs of waves with negative potential values, which were attributed to the WVI/WV redox processes in the polyoxotungstate framework. Redox studies of the cerium derivative revealed the presence of two types of cerium ions.

DNA BINDING STUDIES OF MAGNESIUM(II), CALCIUM(II), BARIUM(II) AND ATP COMPLEXES

Abstract We have investigated the ways by which magnesium (II), calcium (II) and barium (II) and their ATP complexes bind to B-DNA. Effects on native calf thymus DNA conformation were studied and compared with those involving the uncomplexed metal ions and the polymer. It was found that MgATP−2, CaATP−2 and BaATP−2, interact with the phosphates of the polynucleotide; only BaATP −2 appears to bind also through the bases. ATP complexes cause transitions mainly to the B family. The C form is induced by small amounts of MgATP −2 or CaATP−2. At high complex concentrations (r = 2.5 or 5) the polynucleotide adopts the ψ conformation, while BaATP−2 induces this transition at r = 0.6. A contribution of the A form is observed in the case of CaATP-DNA at r = 0.6 and at the beginning of the reaction in the Ba-DNA system at 22°C, for r = 5. The alkaline earth metal ions induce a stabilization of the B conformation. Structural changes with magnesium (II) at r = 2.5 are interpreted in terms of a B to C transition. Calci...

REACTIONS OF THE RHODIUM TRIFLUOROACETATE DIMER WITH NUCLEOSIDES AND NUCLEOTIDES

Abstract Complexes of rhodium trifluoroacetate with adenosine (ado), adenosine-5′-momophosphate (AMP), cytidine (cyd), guanosine (guo) and inosine (ino) have been prepared from aqueous or methanolic solutions. They were characterized by elemental analysis, magnetic susceptibility measurements, mass spectra, infrared, visible and nuclear magnetic resonance spectroscopies. In some cases their formation was followed by NMR prior to isolation. They all proved to be diamagnetic and in every compound contain two ligand molecules per rhodium dimer except for the ado complex where the ratio is 1:1. In the solid state it was found that adenosine interacts with the metal via the N(1) and N(7) atoms, its nucleotide through N(7), whereas in the case of cyd, guo and ino their exocyclic oxygen atoms take part in coordination. Solution study seem highly interesting since in some cases more than one species appear.