Biomedical subjects

Ricardo Baggio

Publications and source records attributed to Ricardo Baggio.

At least 19 recordsLinked to original sources

PubMed2006

Cyano-stabilized triphenylphosphonium ylids.

Crystalline cyano-stabilized triphenylphosphonium ylids with keto or ester groups give rise to an extended electronic delocalization. In methyl 2-cyano-2-(trimethylphosphonio)ethenoate, Ph3P=C(CN)CO2CH3 or C22H18NO2P, (I), and 1-cyano-1-(trimethylphosphonio)prop-1-en-2-olate, Ph3P=C(CN)CO-CH3 or C22H18NOP, (II), the carbonyl groups are oriented toward the cationoid P atom. Bond lengths and angles, torsion angles and P...O contact distances are consistent with a dominant coplanar conformation where the molecular structures are the result of a balance between intra- and intermolecular interactions. The main interactions presented by cyano-ester (I) and cyano-keto (II) are intramolecular interactions between the carbonyl O and the P atoms. In addition, both compounds show other less important intramolecular interactions between the carbonyl O and phenyl H atoms, which could contribute to form a preferred conformation in the crystal structure.

Crystallography, X-Ray↗

PubMed2006

A new simplifying approach to molecular geometry description: the vectorial bond-valence model.

A method to describe, analyze and even predict the coordination geometries of metal complexes is proposed, based on previous well established concepts such as bond valence and valence-shell electron-pair repulsion (VSEPR). The idea behind the method is the generalization of the scalar bond-valence concept into a vector quantity, the bond-valence vector (BVV), with the innovation that the multidentate ligands are represented by their resultant BVVs. Complex n-ligand coordination spheres (frequently indescribable at the atomic level) reduce to much simpler ones when analyzed in BVV space, with the bonus of a better applicability of the VSEPR predictions. The geometrical implications of the BVV description are analyzed for the cases of n=2 and 3 (n=number of ligands), and the validity of its predictions, checked for a large number of metal complexes.

Journal Article↗

PubMed2006

New ruthenium nitrosyl complexes with tris(1-pyrazolyl)methane (tpm) and 2,2'-bipyridine (bpy) coligands. Structure, spectroscopy, and electrophilic and nucleophilic reactivities of bound nitrosyl.

The new compound [Ru(bpy)(tpm)NO](ClO4)3 [tpm = tris(1-pyrazolyl)methane; bpy = 2,2'-bipyridine] has been prepared in a stepwise procedure that involves the conversion of [Ru(bpy)(tpm)Cl]+ into the aqua and nitro intermediates, followed by acidification. The diamagnetic complex crystallizes to exhibit distorted octahedral geometry around the metal, with the Ru-N(O) bond length 1.774(12) A and the RuNO angle 179.1(12) degrees , typical for a {RuNO}6 description. The [Ru(bpy)(tpm)NO]3+ ion (I) has been characterized by 1H NMR and IR spectroscopies (nu(NO) = 1959 cm(-1)) and through density functional theory calculations. Intense electronic transitions in the 300-350-nm region are assigned through time-dependent (TD)DFT as intraligand pi --> pi for bpy and tpm. The dpi --> pi(bpy) metal-to-ligand charge-transfer transitions appear at higher energies. Aqueous cyclic voltammetric studies show a reversible wave at 0.31 V (vs Ag/AgCl, 3 M Cl-), which shifts to 0.60 V in MeCN, along with the onset of a wave of an irreversible process at -0.2 V. The waves are assigned to the one- and two-electron reductions centered at the NO ligand, leading to species with {RuNO}(7) and {RuNO}(8) configurations, respectively. Controlled potential reduction of I in MeCN led to the [Ru(bpy)(tpm)NO]2+ ion (II), revealing a significant downward shift of nu(NO) to 1660 cm(-1) as well as changes in the electronic absorption bands. II was also characterized by electron paramagnetic resonance, showing an anisotropic signal at 110 K that arises from an S = 1/2 electronic ground state; the g-matrix components and hyperfine coupling tensor resemble the behavior of related {RuNO}7 complexes. Both I and II were characterized through their main reactivity modes, electrophilic and nucleophilic, respectively. The addition of OH- into I generated the nitro complex, with k(OH) = 3.05 x 10(6) M(-1) s(-1) (25 degrees C). This value is among the highest obtained for related nitrosyl complexes and correlates with ENO+/NO, the one-electron redox potential. Complex II is a robust species toward NO release, although a conversion to I was observed in the presence of O2. This reaction afforded a second-order rate law with k = 3.5 M(-1) s(-1) (25 degrees C). The stabilization of the NO radical complex is attributed to the high positive charge of the precursor and to the geometrical and electronic structure as determined by the neutral tpm ligand.

2,2'-Dipyridyl↗

PubMed2006

A unique tautomer of 1-n-hexyl-3-phenyl-1H-pyrazol-5-ol.

In the title compound, C15H20N2O, the bond distances and angles are consistent with the presence of the hydroxy tautomer. This tautomer was unambiguously determined by the clear presence of a H atom bonded to oxygen, as well as the total absence of any residual electron density around the N atom in the heterocycle, thus precluding any possibility of desmotropism.

Journal Article↗

PubMed2006

An unusual eight-coordinated copper complex: bis(4,7-diphenyl-1,10-phenanthroline)dinitratocopper(II).

In the title monomer, [Cu(NO3)2(C24H16N2)2], the copper(II) cation is eight-coordinate within an octahedral-like polyhedron. The coordination polyhedron is formed by two chelating diphenylphenanthroline groups that define the highly distorted CuN4 equatorial plane and two weakly bound bidentate (chelating) nitrate groups in the apical or axial positions. The complex crystallizes in the monoclinic space group C2/c; a twofold axis passes through the copper(II) cation and bisects the two nitrate ligands. This gives the molecule C2 point-group symmetry, rendering only half of the molecule independent.

Journal Article↗

PubMed2006

Triaquamanganese sulfite revisited.

Orthorhombic Mn(SO3)(H2O)3 has been reinvestigated by single-crystal X-ray diffraction in two possible space groups, viz. P2(1)2(1)2(1) (with all atoms in general positions) and Pnma (with the molecule bisected by a mirror plane). The results confirm the lower symmetry assigned in a previous single-crystal neutron diffraction study. However, the refinement of the P2(1)2(1)2(1) model requires the introduction of racemic twinning and soft positional and displacement restraints for the H atoms. The importance of a scrupulous report on symmetry absence violations as standard policy in crystallographic work is discussed.

Journal Article↗

PubMed2006

Three oxo complexes with a tetranuclear [Cu(4)(mu(2)-Cl)(6)(mu(4)-O)] unit.

The three title compounds, namely 4-phenyl-1H-imidazolium hexa-mu(2)-chloro-chloro-mu(4)-oxo-tris(4-phenyl-1H-imidazole-kappaN(1))tetracopper(II) monohydrate, (C(9)H(9)N(2))[Cu(4)Cl(7)O(C(9)H(8)N(2))(3)]xH(2)O, hexa-mu(2)-chloro-mu(4)-oxo-tetrakis(pyridine N-oxide-kappaO)tetracopper(II), [Cu(4)Cl(6)O(C(5)H(5)NO)(4)], and hexa-mu(2)-chloro-tetrakis(2-methyl-1H-imidazole-kappaN(1))-mu(4)-oxo-tetracopper(II) methanol trisolvate, [Cu(4)Cl(6)O(C(4)H(6)N(2))(4)]x3CH(4)O, exhibit the same Cu(4)OCl(6) framework, where the O atom at the centre of an almost regular tetrahedron bridges four copper cations at the corners. This group is in turn surrounded by a Cl(6) octahedron, leading to a rather globular species. This special arrangement of the Cu(II) cations results in a diversity of magnetic behaviours.

Cations, Divalent↗

PubMed2006

Two oxo complexes with tetranuclear [Fe(4)(mu(3)-O)(2)](8+) and trinuclear [Fe(3)(mu(3)-O)](7+) units.

Two new oxo complexes, namely hexa-mu(2)-acetato-acetatoaquabis(di-3-pyridylamine)di-mu(3)-oxo-tetrairon(III) chloride monohydrate ethanol 1.25-solvate, [Fe(4)(C(2)H(3)O(2))(7)O(2)(C(10)H(9)N(3))(2)(H(2)O)]Clx1.25C(2)H(6)OxH(2)O, (I), containing a tetranuclear [Fe(4)(mu(3)-O)(2)](8+) unit, and 2-methylimidazolium hexa-mu(2)-acetato-acetatodiaqua-mu(3)-oxo-triiron(III) chloride dihydrate, (C(4)H(7)N(2))[Fe(3)(C(2)H(3)O(2))(7)O(H(2)O)(2)]Clx2H(2)O, (II), with a trinuclear [Fe(3)(mu(3)-O)](7+) unit, are presented. Both structures are formed by two well differentiated entities, viz. a compact isolated cluster composed of Fe(III) ions coordinated to O(2-) and CH(3)CO(2)(-) anions, and an external group formed by a central Cl(-) ion surrounded by different solvent groups to which the anion is bound through hydrogen bonding. In the case of (I), charge balance cannot be achieved within the groups, so the structure is macroscopically ionic; in the case of (II), in contrast, each group is locally neutral owing to the internal compensation of charges. The trinuclear complex crystallizes with the metal cluster, chloride anion and 2-methylimidazolium cation bisected by a crystallographic mirror plane.

Ferric Compounds↗

PubMed2006

Aqua(thiosulfato-kappa2O,S)[2,4,6-tri-2-pyridyl-1,3,5-triazine-kappa3N2,N1,N6]zinc(II) hemihydrate.

The title compound, [Zn(S2O3)(C18H12N6)(H2O)].0.5H2O, contains two almost identical independent monomeric moieties composed of an octahedral Zn centre coordinated by a tridentate 2,4,6-tri-2-pyridyl-1,3,5-triazine (tpt) ligand, one aqua ligand and an O,S-chelating thiosulfate anion. The structure is stabilized by a solvent water molecule. Multiple strong hydrogen bonds with additional weaker pi-pi interactions between tpt groups define a multiple column spatial organization.

Journal Article↗

PubMed2006

Di-mu2-sulfito-kappa8O,O':O',O''-bis[(2,4,6-tri-2-pyridyl-1,3,5-triazine-kappa3N2,N1,N6)cadmium(II)] octahydrate.

The title compound, [Cd2(SO3)2(C18H12N6)2].8H2O, is a dimer built up around a symmetry center, where the sulfite anion displays a so far unreported coordination mode in metal-organic complexes; the anion binds as a mu2-sulfite-kappa4O,O':O',O'' ligand to two symmetry-related seven-coordinate Cd(II) cations, binding through its three O atoms by way of two chelate bites with an O atom in common, which acts as a bridge. The cation coordination is completed by a 2,4,6-tri-2-pyridyl-1,3,5-triazine ligand acting in its usual tridentate mode.

Journal Article↗

PubMed2006

Crystal structure and electronic and magnetic properties of hexacyanoosmate(III).

The [Os(III)(CN)6]3- anion is prepared by chemical oxidation in aqueous solution and isolated as yellow prisms of [Ph4P]3[Os(III)(CN)6].6H2O (1). This species crystallizes in the triclinic space group P with cell parameters a = 13.7609(11) A, b = 16.2275(13) A, c = 17.0895(14) A, alpha = 91.4040(10) degrees , beta = 109.3600(10) degrees , gamma = 102.3970(10) degrees , V = 3497.4(5) A(3), and Z = 2. The slightly distorted octahedral moiety displays Os-C and C-N bond lengths that average 2.058 and 1.146 A, respectively. Spin-orbit-coupling splitting of the ground-state term dominates the NIR region of the electronic spectrum and the magnetic behavior of 1. The experimental information points to higher spin delocalization over the coordinated cyanides than in [Fe(III)(CN)6]3-.

Journal Article↗

PubMed2006

Two one-dimensional zinc(II) coordination polymers: catena-poly[[bis(pentane-2,4-dionato-kappa2O,O')zinc]-mu-1,4-bis(x-pyridyl)-2,3-diazabuta-1,3-diene] (x = 3, 4).

The structures of the two title isomeric compounds, [Zn(C5H7O2)2(C12H10N4)]n, are built up around two non-equivalent symmetry centres, one of them at the cation position and the other bisecting the N-N bond in the 1,4-bis(3/4-pyridyl)-2,3-diazabuta-1,3-diene (3pdb/4pdb) units. Both Zn cations have the Zn atoms an inversion centres and present tetragonally distorted octahedral environments, but differences in their linkage through the 3pdb and 4pdb ligands give rise to differently shaped weakly interacting chains.

Journal Article↗

PubMed2006

An oximino tautomer of 1-n-decyl-4-hydroxyimino-3-methyl-1H-pyrazol-5(4H)-one.

The title compound, C14H25N3O2, consists of a five-membered heterocyclic ring to which a pendant decyl group is attached. The oximino tautomeric character of the molecule is clearly defined by the distribution of well defined double bonds in the heterocycle region (one C=O and two C=N). The most conspicuous packing interaction is the strong intermolecular hydrogen bond linking the oximino OH group and the carbonyl O atom to define broad planar hydrophilic strips running along the unique b axis. The alkyl chains adopt a fully extended conformation and lie almost at right angles to these one-dimensional structures, defining their hydrophobic counterpart.

Journal Article↗

PubMed2005

Gadolinium and neodymium citrates: evidence for weak ferromagnetic exchange between gadolinium(III) cations.

A new lanthanide citrate motif of general formula [Ln(Hcit)(H2O)2.H2O]n, where Ln = Gd (1) and Nd (2) and Hcit3- = C(OH)(COO-)(CH2COO-)2, has been synthesized hydrothermally from Ln2O3 and citric acid at 100 degrees C and characterized by elemental analysis, IR, TG-DTA, single-crystal X-ray diffraction, and magnetic measurements. The structures can be seen as "ladder chains" along the a axis, with dinuclear Ln2O2 units serving as "steps" and R-COO groups as "uprights", which are connected by H bonds. The magnetic susceptibility between 2 and 300 K and the magnetization at 2 K, as a function of magnetic field between 0 and 5 T, were measured for both compounds. By modeling the magnetic behavior of the Gd compound with a dinuclear Hamiltonian [symbol: see text](S) = gmu(B)(S(A) + S(B))B(o) - J(o)S(A)S(B) (S(A) = S(B) = 7/2), a ferromagnetic exchange interaction J(o) = 0.039 cm(-1) was evaluated between Gd ions situated at d(o) = 4.321 angstroms in dinuclear units bridged by two symmetry-related tridentate carboxylate oxygens. The EPR spectrum of the Gd compound is discussed. The temperature dependence of the susceptibility of the Nd compound is caused by the depopulation of the excited crystal-field levels when the temperature decreases. The magnetic-field dependence of the magnetization of 2 is attributed to the ground-state Kramers' doublet populated at 2 K. The g factor of this ground-state doublet is calculated from the data and compared with values for other compounds reported in the literature.

Cations↗

PubMed2005

catena-poly[[aqua(3,4,7,8-tetramethyl-1,10-phenanthroline-kappa2N,N')cadmium(II)]-mu3-thiosulfato-kappa3S:S:O].

The title compound, [Cd(S(2)O(3))(C(16)H(16)N(2))(H(2)O)](n), presents a polymeric one-dimensional structure running along the P2(1)/c glide direction, with elementary units defined by six-coordinate Cd(II) atoms bonded to three symmetry-related thiosulfate groups, a bidentate tetramethylphenanthroline ligand and one aqua ligand. The bridging thiosulfates bind metal centers through two different sequences, viz. Cd-S-Cd' and Cd'-S'-S'-O'-Cd, defining a closed six-membered ring. Individual chains are held together via pi-pi interactions to generate two-dimensional networks parallel to the (100) plane. These, in turn, are connected by much weaker van der Waals interactions.

Journal Article↗

PubMed2005

Thermal behaviour and stability in Olanzapine.

The stability and thermal behaviour of two anhydrate phases and a new mixed water:DMSO solvate of Olanzapine (2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno-[2,3-b][1,5]benzodiazepine) are studied by different methods: differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and Raman scattering (RS). Single crystal structural data for the latter phase are presented, confirming the presence of the (Olanzapine)(2) dimer as the structural building unit of all known phases of the drug, either anhydrate or solvated. An apparent interconversion between both solid state forms is shown to be an artifact and explained in terms of a melting-recrystallization process.

Antipsychotic Agents↗

PubMed2005

6,19-Sulfur-bridged progesterone analogues with antiimmunosuppressive activity.

Sulfur-bridged pregnanes 6,19-epithioprogesterone, 21-hydroxy-6,19-epithioprogesterone, and the corresponding sulfoxides and sulfones were synthesized and tested as blockers of the immunosuppresive activity of dexamethasone in rat thymocytes. A new one-pot procedure is described for the preparation of 6,19-epithioprogesterone and related compounds by iodocyclization of a 19-sulfanylpregn-5-ene. Antiimmunosuppresive activity was evaluated by the ability of the different steroids to block dexamethasone-mediated apoptosis in thymocytes and dexamethasone-mediated inhibition of the NFkappa-B transcription factor activity. DNA fragmentation and annexin V-FITC positive cells were taken as parameters of apoptosis whereas NFkappa-B activity was tested by the expression of the reporter vector kappaB-luciferase by TNF-alpha in Hela cells. 21-Hydroxy-6,19-epithioprogesterone S,S-dioxide had improved activity in both parameters, while 21-hydroxy-6,19-epithioprogesterone had improved activity only in blocking dexamethasone-induced programmed cell death.

Animals↗

PubMed2005

3-(Triphenylphosphoranylidene)pentane-2,4-dione and diethyl 2-(triphenylphosphoranylidene)malonate.

The title ylides, 3-(triphenylphosphoranylidene)pentane-2,4-dione, C23H21O2P, (I), and diethyl 2-(triphenylphosphoranylidene)malonate, C25H25O4P, (II), differ in the conformations adopted by their extended ylide moieties. In (I), one carbonyl O atom is syn and the other is anti with respect to the P atom, the ylide group is nearly planar, with a maximum P-C-(C=O) angle of 18.2 (2)degrees, and the P-C, C-C and C=O bond lengths are consistent with electronic delocalization involving the O atoms. In (II), both carbonyl O atoms are anti and the ester groups are twisted out of the plane of the near trigonal ylide C atom, reducing delocalization, the largest P-C-(C=O) angle being 30.2 (2)degrees.

Journal Article↗