Metal complexes of thiophene 2-thiocarboxamide. Proton and 13C NMR, IR and electronic spectral studies

The complexes of thiophene 2-thiocarboxamide (TTCA) with some metal chlorides and bromides [M = Ni(II), Zn(II), Cd(II), Hg(II) and Cu(I)] are described. Elemental analyses, magnetic susceptibilities and conductance studies, electronic, IR, proton and 13C magnetic resonance spectra are reported. The results suggest exclusive coordination of TTCA through the thiocarbonyl sulfur. The influence of the thiophene ring on the donor properties of the thioamide are discussed.

Ruthenium(II)-CO complexes of N-[(2-pyridyl)methyliden]-alpha(or beta)-aminonaphthalene: Synthesis, spectral studies, crystal structure, redox properties and DFT calculation

The characterization and properties of trans-(X)-[RuX2(CO)(2)(alpha/beta-NaiPy)] (1, 2) (alpha-NaiPy (a), beta-NaiPy (b); X = Cl (1), I (2)) are described in this work. The structures are confirmed by single crystal X-ray diffraction studies. Reaction of these compounds with Me3NO in MeCN has isolated monocarbonyl trans-(X)-RuX2(CO)(MeCN)(alpha/beta-NaiPy)] (3, 4). The complexes show intense emission properties. Quantum yields of 1 and 2 (phi= 0.02-0.08) are higher than 3 and 4 (phi = 0.006-0.015). Voltammogram shows higher Ru(III)/Ru(II) (1.3-1.5 V) potential of 1 and 2 than that of 3 and 4 (0.8-0.9 V) that may be due to coordination of two pi-acidic CO groups in former. The electronic spectra and redox properties of the complexes are compared with the results obtained by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using polarizable continuum model (CPCM).

Vendors' perspectives of coordination in the information technology offshore outsourcing industry : An exploratory study from the Philippines

This study investigates how offshore information technology (IT) service providers (vendors) coordinate work with their clients (employers) in order to succeed in the global IT offshore outsourcing industry. We reviewed literature on coordination studies, interviewed offshore service providers in the Philippines, and used thematic analysis to analyse coordination practices from the point of view of these individual vendors in a newly industrialized country. We used Olson and Olson's framework on 'collaboration at a distance' as a lens to structure the results. The study provides an understanding of vendors' individual attitudes towards the coordination of distributed work and draws attention to how differences in power affect the work situation of vendors, and by implication all stakeholders. We offer this insight as a way to enhance existing CSCW frameworks, by imbuing them with the perspective of non-equal relationships. The study found that vendors were generally able to produce outputs that satisfy their clients, however these results were only achieved because individuals were willing to take risks and make sacrifices in their personal lives. The relationship was further characterised by a complex interplay between the client's control of the overall work arrangements and the vendors' ability to establish a level of autonomy in their work practices and their flexible use of coordination tools.

Coordination aggregation of mesoaryl substituted porphyrins

Synthesis of the free-base tetrakis (3'-nitro/aminophenyl), (H2TNP/H(2)TAP) has been accomplished and its coordination behaviour towards Mg(II), Co(II), Zn(II) and Ag(II) ions is investigated. Optical and magnetic resonance properties of the metal derivatives MTNP and MTAP reveal that the aminoporphyrins exist as aggregates in solution. The aggregation is promoted by the coordination of the peripheral amino groups to neighbouring metalloporphyrins. Possible structures of aggregated species are proposed from the model studies.

Model studies of Ziegler-Natta olefin polymerization using group 3 and group 4 metallocenes

Evidence for the stereochemical isomerization of a variety of ansa metallocene compounds is presented. For the scandocene allyl derivatives described here, we have established that the process is promoted by a variety of salts in both ether and hydrocarbon solvents and is not accelerated by light. A plausible mechanism based on an earlier proposal by Marks, et al., is offered as an explanation of this process. It involves coordination of anions and/or donor solvents to the metal center with cation assistance to encourage metalcyclopentadienyl bond heterolysis, rotation about the Si-Cp bond of the detached cyclopentadienide and recoordination of the opposite face. Our observations in some cases of thermodynamic racemic:meso ratios under the reaction conditions commonly used for the synthesis of the metallocene chlorides suggests that the interchange is faster than metallation, such that the composition of the reaction mixture is determined by thermodynamic, not kinetic, control in these cases.

Two new ansa-scandocene alkenyl compounds react with olefins resulting in the formation of η³-allyl complexes. Kinetics and labeling experiments indicate a tuck-in intermediate on the reaction pathway; in this intermediate the metal is bound to the carbon adjacent to the silyllinker in the rear of the metallocene wedge. In contrast, reaction of permethylscandocene alkenyl compounds with olefins results, almost exclusively, in vinylic C-H bond activation. It is proposed that relieving transition state steric interactions between the cyclopentadienyl rings and the olefin by either linking the rings together or using a larger lanthanide metal may allow for olefin coordination, stabilizing the transition state for allylic σ-bond metathesis.

A selectively isotopically labeled propylene, CH₂CD(¹³CH₃), was synthesized and its polymerization was carried out at low concentration in toluene solution using isospecific metallocene catalysts. Analysis of the NMR spectra (¹³C, ¹H, and ²H) of the resultant polymers revealed that the production of stereoerrors through chain epimerization proceeds exclusively by the tertiaryalkyl mechanism. Additionally, enantiofacial inversion of the terminally unsaturated polymer chain occurs by a non-dissociative process. The implications of these results on the mechanism of olefin polymerization with these catalysts is discussed.

Structural characterization and luminescence studies of new lanthanide(III) complexes with nicotinic and isonicotinic acid N-oxides

Four new polymeric lanthanide(III) complexes of nicotinic acid N-oxide and isonicotinic acid N-oxide have been synthesized and structurally determined. In the isomorphous compounds [(Ln(L-1)(3) (H2O)(2))(n)]. 4nH(2)O(HL1 = nicotinic acid N-oxide; Ln = Eu, 1; Ln = Er, 2) the lanthanide(III) ions form infinite double chains along the b direction through the coordination of bridging carboxylate and N-oxide groups. The chains are cross-linked through hydrogen bonds between aqua ligands and uncoordinated N-oxide groups and between aqua ligands and lattice water molecules, to form a three-dimensional network. [(Eu(L-2)(2)-(H2O)(4))(n)](NO3)(n). nH(2)O (HL2 = isonicotinic acid N-oxide, 3) has a polymeric structure in which the europium (III) ions are connected into infinite chains by pairs of syn-syn carboxylate groups. Adjacent chains are interlinked by hydrogen bonds between aqua ligands and N-oxide groups to form a layer parallel to the (100) plane, and such layers are connected by hydrogen bonds between nitrate anions and aqua ligands, and between oxide groups and lattice water molecules, into a three-dimensional network. In [(Er-2(L-2)(4)(H2O)(10))](NO3)(2). H2O, 4, dinuclear units are inter-linked into a three-dimensional network through hydrogen bonding between aqua ligands and N-oxide groups of both bidentate bridging and unidentate L-2 ligands. Factors affecting the formation of coordination chains and dinuclear units are discussed. Luminescence properties of 1 and 3 have also been studied. (C) 1998 Elsevier Science Ltd. All rights reserved.

Coordination and movement pathology: models of structure and function

Here we consider the role of abstract models in advancing our understanding of movement pathology. Models of movement coordination and control provide the frameworks necessary for the design and interpretation of studies of acquired and developmental disorders. These models do not however provide the resolution necessary to reveal the nature of the functional impairments that characterise specific movement pathologies. In addition, they do not provide a mapping between the structural bases of various pathologies and the associated disorders of movement. Current and prospective approaches to the study and treatment of movement disorders are discussed. It is argued that the appreciation of structure-function relationships, to which these approaches give rise, represents a challenge to current models of interlimb coordination, and a stimulus for their continued development. (C) 2002 Elsevier Science B.V. All rights reserved.

Solid-state NMR and powder XRD studies of the structure of SAPO-40 upon hydration-dehydration cycles

It is well known that after the removal of the template many porous aluminophosphates and related materials are very sensitive to water.' Depending on the type of structure, reversible or irreversible phase transitions, loss of crystallinity and changes in the coordination of some framework A1 upon rehydration are observed. For example, solid-state NMR shows that the rehydration of SAPO-5 leads to the formation of octahedral Al. Subsequent dehydration restores the initial tetrahedral coordination of Al. Template-free SAPO-37 becomes totally amorphous to X-rays after exposure to water and stays so after subsequent thermal treatment^.,,^ In contrast, Barthomeuf and co-workers have shown recently, that, on hydration, template-free SAPO-34, an analogue of chabasite, shows the opening of some Si-0-A1 bonds, the effect being reversible upon dehydrati~n.T~h e hydrated distorted structure was found to be stable for months with no further modifications and the ordered material could be regenerated by removal of water. Here we wish to report that the structure of template-free SAPO-40 undergoes a similar reversible modification.

The activity of mouse Cerberus like 2 during cardiogenesis - genetic and morphogenetic studies

Cardiogenesis is a delicate and complex process that requires the coordination of an intricate network of pathways and the different cell types. Therefore, understanding heart development at the morphogenetic level is an essential requirement to uncover the causes of congenital heart disease and to provide insight for disease therapies. Mouse Cerberus like 2 (Cerl2) has been defined as a Nodal antagonist in the node with an important role in the Left-Right (L/R) axis establishment, at the early embryonic development. As expected, Cerl2 knockout mice (Cerl2-/-) showed multiple laterality defects with associated cardiac failure. In order to identify the endogenous role of Cerl2 during heart formation independent of its described functions in the node, we accurately analyzed animals where laterality defects were not present. We thereby unravel the consequences of Cerl2 lossof- function in the heart, namely increased left ventricular thickness due to hyperplasia of cardiomyocytes and de-regulated expression of cardiac genes. Furthermore, the Cerl2 mutant neonates present impaired cardiac function. Once that the cardiac expression of Cerl2 is mostly observed in the left ventricle until around midgestration, this result suggest a specific regulatory role of Cerl2 during the formation of the left ventricular myoarchitecture. Here, we present two possible molecular mechanisms underlying the cardiac Cerl2 function, the regulation of Cerl2 antagonist in activation of the TGFßs/Nodal/Activin/Smad2 signaling identified by increased Smad2 phosphorilation in Cerl2-/- hearts and the negative feedback between Cerl2 and Wnt/ß-catenin signaling in heart formation. In this work and since embryonic stem cells derived from 129 mice strain is extensively used to produce targeted mutants, we also present echocardiographic reference values to progressive use of juveniles and young adult 129/Sv strain in cardiac studies. In addition, we investigate the cardiac physiology of the surviving Cerl2 mutants in 129/Sv background over time through a follow-up study using echocardiographic analysis. Our results revealed that Cerl2-/- mice are able to improve and maintain the diastolic and most of systolic cardiac physiologic parameters as analyzed until young adult age. Since Cerl2 is no longer expressed in the postnatal heart, we suggest that an intrinsic and compensatory mechanism of adaptation may be active for recovering the decreased cardiac function found in Cerl2 mutant neonates. Altogether, these data highlight the role of Cerl2 during embryonic heart development in mice. Furthermore, we also suggest that Cerl2-/- may be an interesting model to uncover the molecular, cellular and physiological mechanisms behind the improvement of the cardiac function, contributing to the development of therapeutic approaches to treat heart failures.

Synthesis, crystal structure and thermal studies of catena(L-glutamato)-aqua copper(II) monohydrate

The synthesis. crystal structure and thermal study of the blue catena-(L-glutamato)-aqua copper(II) monohydrate have been reported. The compound crystallizes in P2(1)2(1)2(1) space group and consists of a polymeric three-dimensional network of copper(II) which is coordinated with the amino nitrogen and the carboxylate oxygen Of L-glutamate, the side chain carboxylate oxygen of a neighbouring L-glutamate and the oxygen of a water molecule in the equatorial position. Weak coordination of two additional glutamate oxygen atoms to both the axial positions Completes a distorted octahedron. The crystal structure shows that the lattice water is stabilized by the formation of strong H-bonding network with the coordinated water molecule. Removal and reabsorption of the water molecule have been studied by thermal analysis.

Pharmacophore-based 3D QSAR studies on a series of high affinity 5-HT(1A) receptor ligands

5-HT(1A) receptor antagonists have been employed to treat depression, but the lack of structural information on this receptor hampers the design of specific and selective ligands. In this study, we have performed CoMFA studies on a training set of arylpiperazines (high affinity 5-HT(1A) receptor ligands) and to produce an effective alignment of the data set, a pharmacophore model was produced using Galahad. A statistically significant model was obtained, indicating a good internal consistency and predictive ability for untested compounds. The information gathered from our receptor-independent pharmacophore hypothesis is in good agreement with results from independent studies using different approaches. Therefore, this work provides important insights on the chemical and structural basis involved in the molecular recognition of these compounds. (C) 2010 Elsevier Masson SAS. All rights reserved.

Synthesis, characterization and initial biological studies of a new platinum(II) complex with deoxyalliin

A new platinum(II) complex with deoxyalliin was synthesized and characterized by chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pt(C6H11NO2S)Cl-2] center dot H2O. C-13 NMR, N-15 NMR and infrared spectra of the complex are consistent with coordination of deoxyalliin to Pt( II) through the nitrogen and sulfur atoms forming a square-planar geometry. The complex is soluble in dimethylsulfoxide. Biological analysis for evaluation of a potential cytotoxic effect of the complex was performed using HeLa cells, a human cervix adenocarcinoma-derived cell line. The results were compared with those of a palladium( II) complex previously described.

H-1-N-15 NMR studies of the complex bis(S-allyl-L-cysteinate)palladium(II)

H-1-N-15 2D NMR data for S-allyl-L-cysteine (deoxyalliin) and for bis(S-allyl-L-cysteinate)palladium(II) complex are presented in this manuscript. Large upfield N-15 NMR shift of the amine nitrogen in the spectrum of the complex when compared to the spectrum of the ligand shows clearly coordination of S-allyl-L-cysteine, in the anion form, to palladium(II) through the NH2 group. (c) 2005 Elsevier B.V. All rights reserved.

Chemical, spectroscopic characterization, and in vitro antibacterial studies of a new gold(I) complex with N-acetyl-L-cysteine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chemical and spectroscopic studies of a new palladium(II) complex with N-acetyl-L-cysteine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)