1,720,967 research outputs found
Novel Coordination Frameworks Based on Polytopic Heteroaromatic Nitrogen and Carboxylate Ligands
No full textMetal-organic frameworks (MOFs) are comprised of metal clusters and organic ligands. MOFs, similar to zeolite, carbon nanotubes, and activated carbon, have very porous structures. Since MOFs have many more building blocks than materials such as zeolite, their properties can be finely tuned through a careful choice of the ligands. The functionalization of the MOF could be achieved by modifying ligands before the MOF synthesis (pre-synthetically) or after the synthesis (post-synthetically). These functionalized MOFs can be used for numerous applications such as gas storage, gas separation, and catalysis. The advantage of these hybrid materials, over classical (natural and synthetic) porous species (zeolites, active carbons, silica, etc.) resides in the possibility of easy optimization and fine tuning of their functional properties by using modification or substitution strategies of the organic ligands, and through the choice of suitable metallic ions [1, 2]. Moreover, the simultaneous presence of channels (or cavities) and metal ions capable of catalytic activity makes these materials particularly intriguing as heterogeneous catalysts for the transformation of small molecules, and, if the pores are suitably “decorated”, they can display significant size-, regio-, and enantioselectivity [3-6]. In this work we report the synthesis and characterization of a series of pyrazolylbased ligands, namely 3,3',5,5'-tetramethyl-1H,1'H-4,4'-bipyrazole (H2Me4BPz), 1H-pyrazole-3,4,5-tricarboxylic acid (H4PzTc), 1H,1'H-4,4'-bipyrazole (H2Pz) and their MOFs with late transition metals (Co2+, Ni2+, Zn2+, Cu2+, Ru++) characterized by the presence of diverse counterions
Application of metal − organic frameworks
Full text linkThe burgeoning field of metal-organic frameworks or porous coordination polymers has received increasing interest in recent years. In the last decade these microporous materials have found several applications including storage and separation of gases, sensors, catalysis and functional materials. In order to better design new metal-organic frameworks and porous coordination polymers with specific functionalities a fundamental issue is to achieve a basic understanding of the relationship between molecular parameters and structures, preferred adsorption sites and properties by using using modern theoretical methods. The focus of this mini-review is a description of the potential and emerging applications of metal-organic framework
Syntheses and biological studies of nitroimidazole conjugated heteroscorpionate ligands and related Cu(I) and Cu(II) complexes
No full textCopper(I) and copper(II) complexes of 5-nitroimidazole conjugated heteroscorpionate ligands have been synthesized. In particular, the new 2,2-bis(pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide ligand (LHMN) was synthesized by direct coupling of preformed side chain acid with 5-nitroimidazole and its coordination chemistry was investigated towards Cu(I) and Cu(II) acceptors and compared with that of the related 2,2-bis(3,5-dimethyl-1-H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide ligand (LMeMN). The copper(II) complexes [(LMeMN)2Cu]Cl2 and [(LHMN)2Cu]Cl2 were prepared by the reaction of CuCl2·2H2O with LHMN or LMeMN ligands in methanol solution. The water soluble copper(I) complexes [(LMeMN)Cu(PTA)2](PF6) and [(LHMN)Cu(PTA)2](PF6) were prepared by the reaction of Cu(CH3CN)4PF6 and 1,3,5-triaza-7-phosphaadamantane (PTA) with LHMN or LMeMN ligands in acetonitrile solution. The new Cu(I) and Cu(II) complexes as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity against 2D monolayer cultures of multiple human cancer cell lines and 3D-cultured HCT-15 colon cancer spheroids. Morphological analysis by Transmission Electron Microscopy (TEM) revealed the induction of a massive cytoplasmic vacuolization consistent with a paraptotic-like cancer cell death
Development of a Method for Analysing Volatile Compounds in Sparkling Red Wines: Application to the “DOCG Vernaccia di Serrapetrona”
No full text“Vernaccia di Serrapetrona” is an appreciated sparkling red wine produced in Marche Region (Italy), in a small area of the hinterland. The grapes for its production should be composed by at least 85 % “Vernaccia Nera” as established in its production's technical policy, acknowledging the certification DOCG (“Denominazione di Origine Controllata e Garantita”)1 to this wine. The aroma of this “spumante” red wine derives from the volatile compounds either specific to the grapes, formed during the different fermentation steps, and also during the aging. By determining its volatile composition, typical markers could be identified, making the product recognizable and affording tools to safeguard this DOCG wine, never evaluated from this point of view3. Thus, we are developing an HS-SPME-GC method to identify and quantify the volatile compounds in sparkling red wines and particularly in the local product “Vernaccia di Serrapetrona”. Among the most abundant volatiles (esters, alcohols, phenols, hydrocarbons, organic acids), the identity of more than twenty compounds has been confirmed and several parameters are being evaluated for the method optimization, as fiber coating, extraction time and temperature, salt type. The effect of an additional adsorbent phase in the system HS - fiber coating - sample is also being under consideration. Results will be presented and discussed
Synthesis and Characterization of New Ruthenium(II) Arene Acylpyrazolone Complexes
No full textArene ruthenium(II) complexes have been widely studied in the recent years, and their chemistry has been extensively studied for arenes such as benzene and para-cymene. They have found applications in catalysis, supramolecular assemblies, molecular devices.1 Moreover, they have shown antiviral, antibiotic and anticancer activities.2 Recently, mononuclear Ru-acylpyrazolone complexes have been shown to exhibit interesting in vitro activity in some cancer cells.3 On the basis of the our previous work,4 we extend our investigation to the interaction of several acylpyrazolones ligands with (arene)ruthenium(II)dichloride acceptors and PTA (1,3,5-triaza-7-phosphaadamantane)(Figure 1). Their structures have been confirmed by analytical and spectral data. X-ray diffraction studies and their biological activity are under investigation
Design, synthesis and biological evaluation of chemical swiss tools to treat tumors
No full textPolydentate nitrogen-containing donor ligands derived from poly(pyrazol-1-yl)methanes bearing organic functional groups on the bridging carbon have recently attracted considerable attention and their coordination chemistry towards main group and transition metals have been extensively studied. We have synthesized three carboxylated heteroscorpionate ligands, [HC(CO2H)(pzMe2)2], [HC(CO2H)(pz)2] and [HC(CO2H)(tz)2] and we have studied their coordination chemistry towards copper(II), copper(I) and silver(I) acceptors. We have also investigated the use of nitroimidazole (2-methyl-5-nitro-imidazole) as biomolecule to link to scorpionate ligands, as nitroimidazole conjugates of bis(thiosemicarbazonato)copper(II) showed additive or synergistic selectivity for tumor hypoxia compared to their individual components. In particular, we designed two new nitroimidazole conjugated heteroscorpionate ligands, 2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide (LMN) and 2,2-bis(1H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide (LMN’), useful for the synthesis of novel copper(I) and copper(II) derivatives to be evaluated for their cytotoxic activity.3 The ligands [HC(CO2H)(pzMe2)2] and [HC(CO2H)(pz)2] have also been functionalized with the potent NMDA receptor antagonist (6,6-diphenyl-1,4-dioxan-2-yl)methanamine, which showed a significant cytotoxic activity on MCF7 human breast cancer cell lines, highly expressing NMDA receptors.4 Some new copper(II) complexes as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity towards a panel of several human tumour cell lines
The Hg(3,3'-dimethyl-1H,1H'-4,4'-bipyrazolate) coordination polymer: Synthesis, crystal structure and thermal behavior
No full textThe novel coordination polymer Hg(Me2BPZ) (H2Me2BPZ=3,3'-dimethyl-1H,1'H-4,4'-bipyrazole) was prepared by reacting the H2Me2BPZ ligand and mercury(II) acetate. The crystal structure of Hg(Me2BPZ), determined by powder X-ray diffraction with laboratory instrumentation, is characterized by a (4,4)-connected 3-D polymeric network, in which the metal ions show a see-saw stereochemistry. Investigating the thermal behavior by thermogravimetric analysis and variable-temperature powder X-ray diffraction revealed that the material is stable up to 340°C, both under nitrogen and in air, and undergoes a volumetric thermal expansion amounting to â1⁄42% before losing crystallinity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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