M.A. Romero-Molina

Transition metal complexes with monodeprotonated isoorotic and 2-thioisoorotic acids: Crystal structure, spectral and magnetic study, and antimicrobial activity

Abstract The reaction, in ethanol or water medium, of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), and Pt(II) ions with isoorotic and 2-thioisoorotic acids (H 3 L) has allowed the isolation of complexes with the general formula M II (H 2 L) 2 ·2H 2 O. These were characterized by means of elemental analysis, spectral techniques (UV-Vis-NIR, IR, EPR, 13 C and 1 H NMR), magnetic moments, and conductivity measurements. The molar conductivities in dimethylsulphoxide indicate the non-ionic nature of isolated compounds. The most common coordination mode of uracil monoanions seems to be a O4-OCO bidentate scheme which leads to a six-membered chelate ring. Complexes of first row transition ions display an octahedral structure, whereas for Pd(II) and Pt(II) compounds a square-planar structure is suggested. The MO 6 octahedral structure has been corroborated from the single crystal x-ray study of bis-isoorotato-diaquazinc(II). This compound is monoclinic, space group P2 1 /c, with a = 5.067(5) A, b = 15.072(4) A, c = 11.239(8) A, β = 125.80(9)°, V = 696(1) A 3 , and Z = 2. The structure was solved by means of the heavy atom method from the zinc special position. Full matrix refinements based on F o were performed to R = 0.060 for 1884 data. The structure consists of discrete [Zn(H 2 CU) 2 (H 2 O) 2 ] units in which the Zn(II) ion is octahedrally MO 6 coordinated by two bidentate O4-OCO isoorotato ligands (Mue5f8O, 2.033 and 2.039 A) and two water molecules occupying the axial positions (Mue5f8O w , 2.170 A). Likewise, a previous study of biological activity of these complexes against several bacteria and yeasts was carried out. In general, complexes with the 2-thioisoorotato ligand possess greater antimicrobial activity than those with the isoorotate ligand, specially in the case of cobalt(II) complexes.

Thermal studies on purine complexes. III. Palladium complexes of xanthine and some xanthine derivatives

Abstract Some complexes |PdL 2 Cl 2 | (where L = xanthine, theophylline, theobromine, 3,8-dimethylxanthine, caffeine and 1,3,8-trimethylxanthine) have been prepared in acid medium. Their structure has been established from IR and 1 H-NMR data. The thermal behaviour of these complexes has been studied by TG, DTG and DSC techniques. Heats of dehalogenation have been calculated from the DSC curves.

Synthesis, molecular structure determination, and biological studies on E-1-p-ethoxyphenyl-4-hydroximinomethyl imidazole metal complexes

Metal complexes of E-1-p-ethoxyphenyl-4-hydroximinomethyl imidazole (EALDH) were prepared and characterized by infrared, electronic, 1H and 13C NMR two-dimensional spectroscopy, and magnetic and thermal measurements. In all the complexes the organic ligand acts as a chelating agent through N3imid and Noxime atoms, except in the Ag(I) complex, where the coordination takes place monodentately through the N3 atom of the imidazole. Antimicrobial activities of the complexes against Pseudomonas, E. coli, Proteus, Salmonella, Micrococcus, Staphylococcus, Bacillus, and Candida were performed as a previous step in the study of their biological activities.

Comportement thermique des quelques complexes metalliques avec les dianions isoorotate et 2-thioisoorotate

Abstract The thermal behaviour of M II (HL)· x NH 3 · y H 2 O complexes (HL = isoorotate and 2-thioisoorotate; M = Mn, Ni, Cu, Zn, Cd, Hg) has been established by TG, DTG and DSC methods. The thermal decomposition of these compounds takes place through two major steps. The first is loss of solvent molecules and this is followed by decarboxylation and pyrolytic decomposition. TG and DSC data suggest that solvent molecules are not structurally well defined, in spite of the fact that spectral data indicate that in most cases these water and ammonia molecules are coordinated to the metal ion. Wherever possible, the nature of intermediate products and residues was investigated by infra-red spectrometry.

Synthesis, characterization, and crystal structure of 1,3,7,9-tetramethylpyrido-[2,3-d∶6,5-d′]-dipyrimidine-2,4,6,8-tetrone

A new and easy method for the preparation of 1,3,7,9-tetramethylpyrido-[2,3-d∶6,5-d′]-dipyrimidine-2,4,6,8-tetrone is described. The structure of this compound has been solved by means of X-ray diffraction methods. The chemical characterization by spectral (mass, ultraviolet, infrared, and proton nuclear magnetic resonance) and thermal (thermogravimetry and differential scanning calorimetry) method is also reported. The compound is monoclinic, space groupP21/c,a=12.720(5),b=13.688(7),c=8.079(2) Å, β=107.06(4)°,Z=4. The structure consists of discrete tricyclic molecules, stacking playing an important role in crystal packing.

Thermal analysis applied to the study of metal complexes: thermal behaviour of 6-amino-2-thiouracil and its complexes with several transition metal ions

Abstract The thermal decomposition processes of 6-amino-2-thiouracil and its Co(II), Ni(II), Cu(I), Ag(I), Zn(II), Cd(II) and Hg(II) complexes have been studied by TG and DSC techniques. Heats of dehydration have been calculated from the DSC curves. Infrared spectroscopy applied to some of these complexes heated in air has elucidated the decomposition steps and the nature of the intermediate products. The pyrolysis of these compounds ends between 600 and 800°C with different products as final residues.

Zn(II), Cd(II) and Hg(II) complexes of 6-amino-1-methyl-5-nitrosouracil

Abstract The following Zn(II), Cd(II) and Hg(II) complexes of neutral and deprotonated 6-amino-1-methyl-5-nitroso-uracil (HL) were prepared and studied by u.v.-vis, 1H-NMR and i.r. techniques: ZnL2·4H2O,ZnL2(H2O)2·H2O, CdCl2(HL)2·2H2O and HgL2·2H2O. In Zn(II) and Hg(II) complexes, the ligand is coordinated in anionic nitroso-phenolic form, acting as a bidentate ligand through the nitrogen and oxygen atoms of the 5-nitroso and 6-oxide groups, respectively. In the cadmium complex, the ligand seems to be either N,O- or only N-bound to the metal ion, with chlorine bridging. From the data obtained, molecular structures are proposed for each complex.

Thermal studies on metal complexes of 5-nitrosopyrimidine derivatives. IV: Complexes of Fe(II), Co(II), Ni(II) and Cu(II) with 6-amino-5-nitrosouracil

The thermal decomposition processes of the complexes of 6-amino-5-nitrosouracil with Fe(II), Co(II), Ni(II) and Cu(II) have been studied using TG and DSC techniques. Dehydration energies have been calculated from the DSC curves.ZusammenfassungDie thermischen Zersetzungsprozesse von Komplexen von 6-Amino-5-nitrosouracil mit Fe(II), Co(II), Ni(II) und Cu(II) wurde mittels TG und DSC untersucht. Aus den DSC-Kurven wurden die Dehydratisierungsenergien berechnet.РезюмеМетодом ТГ и ДСК изуче ны процессы термического разлож ения комплексов 6-амин о-нитрозоурацила с двухвалентными жел езом, кобальтом, никелем и м едью. На основе кривых ДСК вычислены энергии дегидратаци и.

Thermal and spectral studies on hexachloroplatinates(iv) of some alkyl-xanthimes

Abstract Hexachloroplatinates of xanthine (XH), theobromine (TBH), theophylline (TFH), 1,3,8-trimethyl-xanthine (TMH), caffeine (CF) and 8-ethyl-theophylline (ETH) have been synthesized and studied by IR, H-NMR, TG and DSC techniques. In all cases, the purine derivatives acts in monoprotonated for and is not bound to metal ion, forming a salt-like structure.

Thermal studies on alkaline earth monomethyl violurates

Abstract Some alkaline earth monomethyl violurate hexahydrates were prepared in aqueous medium, and characterized on the basis of elemental analysis and IR spectral data. The thermal behaviour of these salts was studied with the aid of TG, DTG and DSC techniques. Heats of dehydration were calculated from DSC curves.