Miguel Quirós-Olozábal

Metal complexes with the ligand derived from 6-acetyl-1,3,7-trimethyllumazine and benzohydrazide. Molecular structures of two new Co(II) and Rh(III) complexes and analysis of in vitro antitumor activity.

The structures and spectroscopic properties of new Mn(II), Co(II), Cd(II), Hg(II), Ag(I), Rh(III), and Ir(I) complexes with the ligand BZLMH derived from 6-acetyl-1,3,7-trimethyllumazine (lumazine=pteridine-2,4(1H,3H)-dione) and benzohydrazide are reported. Complexes have been characterized by elemental analyses, spectroscopic studies (IR, UV-vis, (1)H, (13)C and (15)N NMR) and magnetic measurements. In all the complexes, the lumazine-derived ligand appears to be coordinated in either tridentate (N5, N61 and O63) or tetradentate forms (O4, N5, N61 and O63). The molecular structures of the [Co(BZLMH)(H(2)O)(CH(3)CN)(2)](ClO(4))(2) x CH(3)CN and [RhCl(2)(BZLM)(CH(3)CN)] x CH(3)CN complexes, determined by single crystal X-ray diffraction, have allowed to corroborate both coordination behaviours. The cytotoxic activity of the free ligand and complexes against human neuroblastoma NB69 cell line is also described. The differential analysis of the initial cytotoxic screening data has shown good activity only for the [RhCl(2)(BZLM)(CH(3)CN)] x CH(3)CN compound at concentrations at around 2 microM; for the other complexes, a modulation of the cell growth was not found upon complexation, this non-specific effect strongly suggesting an apoptotic behaviour.

Synthesis and characterization of new complexes formed between 1-methyllumazine and 1,6,7-trimethyllumazine ligand with transition metal(II) nitrate. Crystal structure of cobalt(II), copper(II) and cadmium(II) complexes

Abstract The structures and spectroscopic properties of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) nitrate complexes of 1-methyllumazine (MLM) and 1,6,7-trimethyllumazine (MLMD) with general formula M(II)(NO 3 ) 2 L 2 · n H 2 O are reported. In all the complexes, the lumazine-derived ligands seem to be coordinated in bidentate form through the N5 and O4 atoms. The crystal structures of [Cu(MLM) 2 (H 2 O) 2 ](NO 3 ) 2 ( 1 ), [Co(MLMD) 2 (H 2 O) 2 ](NO 3 ) 2 ( 2 ) and [Cd(MLMD) 2 (NO 3 ) 2 ] ( 3 ) have been determined by X-ray crystallographic methods. In compounds 1 and 2 the nitrate anions are uncoordinated, and the metal ions are surrounded in an octahedral geometry by two bidentate lumazine ligands and two coordinated water molecules. The absolute configuration of the complex 1 can be described as the 4M stereoisomer, following Bailars nomenclature, with the two lumazine in a cis arrangement and the complex 2 exhibits the 2L stereoisomer as is usually in this kind of complexes. Compound 3 consists of neutral mononuclear units, the Cd(II) environment being a bicapped octahedral close to the trigonal antiprism due to the two nitrate anions coordinating in a very unsymmetrical bidentate mode.

Synthesis and structural studies on metal nitrate complexes with 1,3-dimethyllumazine and 1,3,6,7-tetramethyllumazine: crystal structure of two new cobalt(II) and copper(II) three-dimensionally hydrogen-bonded complexes and a cadmium(II) complex with unusual geometry

Abstract In absolute methanol medium, M II (NO 3 ) 2 (M = Co,Ni,Cu,Zn and Cd) react with 1,3-dimethyllumazine (DLM) and 1,3,6,7-tetramethyllumazine (DLMD) (lumazine = (1 H ,3 H )-pteridin-2,4-dione) to give complexes with general formula M II (NO 3 ) 2 (pteridine) 2 · n H 2 O. These compounds have been characterized by means of the analytical techniques (elemental analysis and thermogravimetry), spectral methods (IR, 13 C and 1 H NMR, UV-Vis-NIR, EPR) and magnetic measurements (77–290 K). Single-crystal X-ray diffraction studies have been made on the complexes [Co(DLM) 2 (H 2 O) 2 ](NO 3 ) 2 ·2H 2 O, [Cu(DLMD) 2 (H 2 O) 2 ](NO 3 ) 2 ·2H 2 O and [Cd(NO 3 ) 2 (DLMD) 2 ]. Cobalt and copper complexes crystallize in the monoclinic system (space group P 2 1 / n , Z = 2) with a = 8.746(1), b = 13.584(2), c = 10.997(1) A , β = 94.89(1)°, V = 1301.8(3) A 1 , and R = 0.057 for 3787 independent reflections with l >2 σ (1) and 202 parameters (Co/DLM complex) and a = 8.9929(7), b = 1.0574(9), c = 11.9242(7) A , β = 98.124(5)°, V = 1492.3(2) A 1 , and R = 0.039 for 2612 independent reflections with l >2 σ ( l ) and 230 parameters (Cu/DLMD complex). In both complexes, the metal ion occupies an inversion center and exhibits an octahedral coordination. The Co(II) coordination octahedron is tetragonally flattened, but the Cu(II) coordination is rhombically distorted. The equatorial plane consists of two N(5) and two O(4) atoms of pteridine ligands and the two axial sites are occupied by two oxygen atoms from the coordinated water molecules. The monomeric units together with non-coordinated water molecules and nitrate anions are involved in a complex three-dimensional H-bond network. The cadmium complex crystallizes in the monoclinic system (space group P 2 1 / c , Z = 2) with a = 8.5689(4), b = 18.5279(9), c = 8.6209(3) A , β = 106.894(3)°, V = 1309.6(1) A 3 , and R = 0.030 for 1260 independent reflections with l >2 σ ( l ) and 192 parameters. The structure consists of monomeric centrosymmetric units in which the cadmium atom is eight-coordinated by four nitrate oxygen atoms of two bidentate nitrate anions and two N(5)-O(4) lumazine bidentate ligands. The geometry of the coordination polyhedron could be described as an octahedron whose equatorial plane is formed by two bidentate N(5)-O(4) pteridine ligands and whose apical positions each seem to be split into two coordination positions occupied by bidentate nitrate ligands.

Crystal structure, raman and 57Fe mo¨ssbauer spectra of the FeII complex of iso-orotic acid

Abstract The crystal structure of [Fe(H 2 isoor) 2 (H 2 O) 2 ]·2H 2 O has been solved by single-crystal X-ray diffractometry. Thermogravimetric analysis shows simultaneous loss of all water molecules between 120 and 266°C, followed immediately by a rapid degradation of the compound. A comparative analysis of the Raman spectra of the complex with that of free-iso-orotic acid allowed a straightforward assignment of the vibrations of the ligand groups involved in coordination. The 57 Fe Mo¨ssbauer spectrum of the complex confirms the presence of a high-spin Fe II ion and the distortion of the octahedral Fe II environment.

Versatile coordinative abilities of a new hybrid pteridine-thiosemicarbazone ligand: crystal structure, spectroscopic characterization, and luminescent properties.

The synthesis and characterization of the first thiosemicarbazone-lumazine (TSCLMH=the thiosemicarbazone of 6-acetyl-1,3,7-trimethyllumazine) hybrid ligand is reported. The influence of the conformation of this compound on its energy and the atomic contribution to the molecular orbitals have been theoretically investigated. Ni(II), Cu(I), Zn(II), and Cd(II) complexes of this ligand have been synthesized and characterized by elemental analysis, thermogravimetric studies, IR, 1H, 13C, and 15N NMR, and UV-vis-NIR spectroscopy, magnetic measurements, and X-ray crystallography. Four types of coordination modes for the ligand may be predicted: (a) double bidentate; (b) tetradentate; (c) tridentate; (d) bidentate. Structures of representative complexes of types a, b, and d have been determined by X-ray crystallography. In the [Cu(TSCLMH)]2(ClO4)2 complex, TSCLMH acts as a doubly bidentate bridging ligand forming a dimer with a Cu...Cu distance of 2.876 A. The geometry around the metal ion is trigonally distorted tetrahedral with a relatively long (four-atom) bridge between the metal centers instead of the shorter, mainly single atom, bridges present in other thiosemicarbazone derivatives complexes. In the [Cd(NO3)2(TSCLMH)(EtOH)] complex, the metal ion displays eight-coordinated geometry with the TSCLMH ligand acting in a tetradentate planar fashion and two nitrate anions, one monodentate and the other bidentate. The coordination polyhedron in [Cd(TSCLM)2(H2O)].MeOH.2H2O is a square pyramid with two monoanionic ligands acting as bidentate NS donors and a water molecule completing the coordination sphere. Fluorescence spectroscopic properties of TSCLMH have been studied as well as the changes in position and intensity of fluorescence bands caused by the complexation with different metal ions (Ni2+, Cu+, Zn2+, Cd2+).

Synthesis and characterization of several lumazine derivative complexes of Co(II), Ni(II), Cu(II), Cd(II), Pd(II) and Pt(II). X-ray structures of a mononuclear copper complex and a dinuclear cadmium complex

The synthesis of the new Co(II), Ni(II), Cu(II), Cd(II), Pd(II) and Pt(II) complexes with 1-methyllumazine (1-methylpteridine-2,4(1 H ,3 H )-dione, MLM) and 1,6,7-trymethyllumazine (1,6,7-trimethylpteridine-2,4(1 H ,3 H )-dione, MLMD) is described. The coordination chemistry of these ligands have been investigated and an usual bidentate bonding mode through the N5 and O4 atoms is observed. These complexes present the form M II Cl 2 L and were characterized by elemental analyses, TG and DSC, as well as by IR, UV–Vis, EPR spectroscopy and magnetic measurements. The crystal structures of [CuCl 2 (MLMD)(H 2 O)] and [CdCl 2 (MLM)(H 2 O)] 2 have been determined by X-ray diffraction methods. The copper(II) compound exists in the monomeric form with an environment around the metal ion as a distorted square-based pyramidal geometry whereas the cadmium complex was observed as dimers with an edge-sharing distorted octahedral coordination sphere around each cadmium center.

Mixed complexes of 6-aminouracil derivatives: Synthesis, spectral properties and crystal structure of 6-amino-1,3-dimethyl-5-nitrosouracilato (N5,N6)-2,2′-bipyridine(N,N′)-ethanol (O)-copper(II) nitrate

Abstract In absolute ethanol medium, copper(II) nitrate reacts with 6-amino-1,3-dimethyl-5-nitrosouracil (HDANU) and 2,2′-bipyridine to give a mixed complex with the formula [Cu(DANU)(bipy)(EtOH)](NO 3 ). This compound has been characterized by means of analytical techniques (elemental analysis and TG), spectral methods (IR, UV-VIS-NIR, EPR), magnetic measurements (77–290 K) and single-crystal X-ray diffraction. The structure consists of monomeric CuN 4 O units in which the copper ion displays a 4 +1 square-pyramidal coordination. The base of the polyhedron is occupied by four nitrogen atoms (Cu-N ca 2 , two from bipy and the other two from 5-nitroso and 6-amino groups of the uracil derivative in the N 6 -mono-deprotonated form, leaving two five-membered chelate rings. In the apical position of the pyramid, an O-coordinated ethanol molecule with a long Cu-O distance (2.248 ) is located, the metallic centre being 0.144above the base of the polyhedron. The nitrate group is out of the coordination sphere, stabilizing the complex by hydrogen bonds formed between the hydrogen atom attached to the ethanolic oxygen and an oxygen atom from the nitrate group. The molecules are stacked as planes perpendicular to the a axis. Copyright

Synthesis, spectral and XRD studies on three O-nitrito-complexes with new N,N,O-tridentate Schiff bases derived from 6-amino-5-formyl-1,3-dimethyluracil and semicarbazide, acetylhydrazine and benzoylhydrazine

Abstract From the reaction between Cu(II) and Zn(II) nitrates and three Schiff bases derived from 6-amino-5-formyl-1,3-dimethyluracil and semicarbazide (H2SDO), acetylhydrazine (H2ACEDO) and benzoylhydrazine (H2BEZDO) in DMF, three nitrito-complexes with simplified formulas [Cu(HSDO)(NO2)] (1), [Cu(HACEDO)(NO2)(H2O)] (2) and [Zn(HBEZDO)(NO2)(H2O)] (3) have been obtained. The appearance of the nitrito ligand may be explained by the reduction of the nitrate anion with the carbon monoxide appearing from the decomposition of DMF at high temperature. In the three compounds, the Schiff base acts as tridentate monodeprotonated ligand through the N(6), N(51) and O(52) atoms, making two five- and six-membered chelate rings. The nitrite anion acts as a monodentate ligand through one oxygen atom giving a square-planar environment (compound 1) in which there are not any additional potential donor atoms under and/or below the coordination plane which permit to establish an elongated tetragonal geometry usually found in Cu(II) complexes. On the contrary, in the molecular unit of the complexes [Cu(HACEDO)(NO2)(H2O)] (2) and [Zn(HBEZDO)(NO2)(H2O)] (3) there is a coordinated water molecule defining a square-pyramidal coordination polyhedron (compound 2) and a distorted trigonal bipyramid (compound 3).

Synthesis and structural studies on three-dimensionally hydrogen-bonded metal perchlorate complexes with 1,3-dimethyllumazine and 1,3,6,7-tetramethyllumazine. Crystal structure of diaqua-bis(1,3,6,7-tetramethyl-pteridine2,4(1H,3H)-dione-O4,N5) copper(II) perchlorate dihydrate

Abstract In aqueous solution, M II (ClO 4 ) 2 (Mn  Mn, Co, Ni, Cu, Zn, Cd and Hg) reacted with 1.3-dimethyllumazine 9DLM) and 1,3,6,7-tetramethyllumazine (DLMD) (lumazine = (1 H ,3 H )-pteridin-2,4-dione) to give complexes with general formula Mp II (ClO 4 ) 2 (LM) 2 · n H 2 O. These compounds have been characterized by means of the analytical techniques (elemental analysis and thermogravimetry), spectral methods (IR, 13 C and 1 H NMR, UV-VIS-NIR, electron paramagnetic resonance) and magnetic measurements (77–290 K). Single-crystal X-ray diffraction studies have been made on the complex [Cu(DLMD) 2 (H 2 O) 2 ](ClO 4 ) 2 ·2H 2 O. This compound crystallizes in the monoclinic system. P 2 1 / c space group, Z = 2, with a = 8.764(1), b = 13.7932(8), c = 14.792(1) A , β = 116.02(1)°, V = 1602.9(3) A 3 , and R = 0.0728 for 4648 independent reflections and 224 parameters. The metal ion occupies an center and exhibits a distorted octahedral coordination. The coordination octahedron is flattened, the equatorial plane consisting of two N(5) and two O(4) atoms of pteridine ligands: the two axial sites are occupied by two oxygen atoms from the coordinated water molecules. The monomeric units together with non-coordinated water molecules and perchlorate anions are involved in a complex three-dimensional H-bonds network, the pteridine moieties being packed following planes roughly parallel to b axis, and perpendicular to the [5 4 21] direction. These planes are separated by a mean distance of 7.3 A.

Spectral and magnetic properties, and biological activity of several coordination compounds of dinegative isoorotato and 2-thiosoorotato ligands. Crystal structure of the tetrameric complex [Cu4(isoorotato2−)4(NH34(H2O2]·4H2O

Abstract The interaction of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) ions with isoorotic and 2-thioisoorotic acids in aqueous ammonia has led to complexes with general formula MnII(HL2−)·xNH3·yH2O. These compounds were characterized by spectral methods, (IR, UV- Vis-NIR and EPR), magnetic moments and conductivity measurements. The most common coordination mode of uracil derivatives seems to be a O4-OCO six-membered chelate ring. The X-ray structure of [Cu4(isoorotato)4(NH3)4(H2O)2]·4H2O consists of tetrameric units; each ligand bridging two metallic centers with the N(3) atom linked to one of the copper atoms and the carboxylate group together with the carbonyl oxygen in position 4 chelating to other; this oxygen also seems to interact weakly with the first copper atom. Each copper atom is strongly coordinated by four atoms in a square-planar fashion, N(3) from one ligand, O(4) and the carboxylate oxygen from another one and an ammonia molecule in trans position to O(4). The weak interaction with O(4) of the first ligand and two weakly coordinated water molecules per tetramer complete a ‘4 + 1’ coordination number for two copper atoms and a ‘4 + 2’ for the other. A previously study of biological activity of these complexes against several microorganisms has been carried out.