1,720,963 research outputs found
COPPER(I) AND SILVER(I) COMPLEXES OF OLEFINS, ALKYNES, AND CYCLOPROPENES AND THEIR APPLICATIONS
Full text linkPoly(pyrazolyl)borates are very popular ligands in organometallic chemistry due to their attractive properties. It is easy to modify the steric and electronic properties of these ligands by changing the pyrazolyl substituents. Fluorinated tris(pyrazolyl)borates are used to stabilize many reactive metal ions. The metal complexes of them are used for multiple applications. These ligands are extensively used to isolate and stabilize many coinage metal complexes (Cu, Ag, and Au). We have synthesized comparably less explored fluorinated bis(pyrazolyl)borate ligands and utilized them to isolate several π-ligands (olefin, alkyne, and cyclopropene) complexes of copper(I) and silver(I). Chapter 2 of this research work focuses on ethylene/ethane separation technology and the development of novel pentafluorosulfanyl supported bis(pyrazolyl)borate ligands. The copper(I) bis(pyrazolyl)borate trimer, {[H2B(3,5-(CF3)2Pz)2]Cu}3, reversibly coordinate ethylene and forms [H2B(3,5-(CF3)2Pz)2]Cu(C2H4). We have studied the chemistry of this transformation both in the solution and solid phase and also how efficiently it can separate ethylene from a mixture of ethylene and ethane. The second part of this chapter focuses on the development of a novel pentafluorosulfanyl supported bis(pyrazolyl)borate ligand, [Ph2B(3-(SF5))Pz)2]-. We have synthesized copper(I) and silver(I) ethylene complexes using this ligand and compared it to the metal complexes of the CF3 analog [Ph2B(3-(CF3)Pz)2]- in a structure and bonding study and also as a catalyst in cyclopropanation reactions. Chapter 3 discusses the synthesis and characterization of several copper(I) and silver(I) alkyne complexes including the rare complexes with acetylene. We have compared the ligand and metal effect on acetylene complexes using various characterization methods such as NMR, Raman, XRD, etc. We have also performed computational studies to support our experimental results. We have utilized one of our copper(I) complexes as a catalyst for the azide-alkyne cycloaddition reaction of various alkynes including acetylene. Chapter 4 describes the synthesis and isolation of novel copper(I) bis(pyrazolyl)borate cyclopropene complexes. These cyclopropane complexes are the first examples of copper(I) η2-cyclopropene complexes. The studies show how the backbonding due to metal coordination effects ring angle and bond lengths of highly strained cyclopropenes. We have shown a copper(I) catalyzed method to synthesize cyclopropenes from alkynes using ethyl diazoacetate
Synthesis and Investigations of the Antitumor Effects of First-Row Transition Metal(II) Complexes Supported by Two Fluorinated and Non-Fluorinated β-Diketonates
Full text linkThe 3d transition metal (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes, supported by anions of sterically demanding beta-diketones, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3), were synthesized and evaluated for their antitumor activity. To assess the biological effects of substituents on phenyl moieties, we also synthesized and investigated the analogous metal(II) complexes of the anion of the less bulky 1,3-diphenylpropane-1,3-dione (HLPh) ligand. The compounds [Cu(LCF3)2], [Cu(LMes)2] and ([Zn(LMes)2]) were characterized by X-ray crystallography. The [Cu(LCF3)2] crystallizes with an apical molecule of solvent (THF) and features a rare square pyramidal geometry at the Cu(II) cen-ter. The copper(II) and zinc(II) complexes of diketonate ligands, derived from the deprotonated 1,3-dimesitylpropane-1,3-dione (HLMes), adopt a square planar or a tetrahedral geometry at the metal, respectively. We evaluated the antitumor properties of the newly synthesized (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes against a series of human tumor cell lines derived from different solid tumors. Except for iron derivatives, cellular studies revealed noteworthy antitumor properties, even towards cancer cells endowed with poor sensitivity to the reference drug cisplatin
Terminal and internal alkyne complexes and azide-alkyne cycloaddition chemistry of copper(I) supported by a fluorinated bis(pyrazolyl)borate
No full textCopper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HC≡CSiMe3 are also reported. They are three-coordinate copper complexes featuring η2-bound alkynes. Raman data show significant red-shifts in C≡C stretch of [H2B(3,5(CF3)2Pz)2 ]Cu(HC≡CH) and [H2B(3,5-(CF3)2Pz)2 ]Cu(HC≡CSiMe3) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu2 (µ-[3,5(CF3)2Pz])2 (HC≡CH)2 display similar Cu-alkyne bonding features. The mononuclear [H2B(3,5(CF3)2Pz)2 ]Cu(NCMe) complex catalyzes [3 + 2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {µ-[3,5-(CF3)2Pz]Cu}3 involving bridging pyrazolates.Universidad Autónoma de Chil
Exploring fluorinated and non-fluorinated β-diketonates: synthesis and biological evaluation of first-row transition metal(II) complexes for cancer treatment
No full textThe β-diketone scaffold, found in natural products like curcuminoids, exhibits exceptional antibacterial, neuroprotective, and anticancer properties in both natural and synthetic analogs. Moreover, β-diketones are known to form complexes with almost every metal, and they have been used as supporting ligands for Ti(IV), Ru(II), Pd(II) and Pt-based anticancer agents. Therefore, drawing inspiration from nature, medicinal inorganic chemistry allows the development of more potent, clinically effective, and less toxic metal-based antiproliferative drugs with improved selectivity towards tumor cells. The substituents on the β-diketonate moiety play a crucial role in modulating the toxic side effects of the resulting complexes. Fluorine-containing compounds are relevant in modern medicinal chemistry, and substituting methyl groups with trifluoromethyl ones in a molecule might be expected to induce great changes in molecular and biological properties. Apart from metal-curcumin complexes, very few studies on the anticancer activity of homoleptic first-row transition metal complexes with β-diketonate ligands have been described in the literature to date. We report here a study on the synthesis, characterization, and biological evaluation of new homoleptic first-row transition metal(II) complexes. In particular, we report the synthesis of Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of the β-diketonate ligands derived from 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3), 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-diphenylpropane-1,3-dione (HLPh). We carried out a screening of the newly synthesized metal(II) compounds against a panel of human cancer cell lines derived from different solid tumors, to investigate the structure-activity relationships. Except for iron derivatives, most showed significant antitumor properties, even against cisplatin-resistant cells
BIOLOGICAL EVALUATION OF Cu(I) AND Ag(I) COMPLEXES WITH β-DIKETONE LIGANDS FEATURING MESITYL AND TRIFLUOROMETHYL SUBSTITUTENTS
No full textRecent advances in medicinal inorganic chemistry have led to the development of innovative chelating ligands and delivery systems to enhance the potency and selectivity of metal-based anticancer drugs. In this regard, group 11 metal complexes have emerged as promising candidates due to their unique therapeutic potential.[1] Although β-diketones represent one of the oldest classes of chelating ligands, their coordination chemistry continues to attract much interest. Therefore, as part of our investigation on the chemical and biological properties of metal-based anticancer complexes supported by β-diketonate ligands,[2,3] we synthesized a series of Cu(I) and Ag(I) complexes stabilized by β-diketone ligands (Figure 1): 1,3-dimesitylpropane-1,3-dione (HLMes), 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3), and 1,3-diphenylpropane-1,3-dione (HLPh). As co-ligands to stabilize the metal in the +1 oxidation state and to modulate lipophilicity, we employed triphenylphosphine (PPh3) and 1,3,5-triaza-7-phosphaadamantane (PTA).
X-ray crystallographic analysis revealed that [Cu(LCF3)(PPh3)2] and [Ag(LPh)(PPh3)2] adopt distorted tetrahedral geometries (Figure 2). The planar CuO2C3 metallacycle of [Cu(LCF3)(PPh3)2] and the half-boat AgO2C3 core of [Ag(LPh)(PPh3)2] point out the variability in coordination environments. While the influence of coordination geometry on biological activity remains to be fully elucidated, the observed differences may contribute to the distinct cytotoxic profiles of these complexes. Biological evaluation demonstrated that Ag(I) and Cu(I) complexes with PPh3 as the phosphane coligand possessed greater antitumor activity against human tumor cell lines derived from solid tumors, compared to cisplatin. Among them, copper complexes with HLCF3 and HLMes ligands were the most active derivatives. Particularly, [Cu(LMes)(PPh3)2] was up to 16 times more active than cisplatin in inhibiting the cell proliferation of 2D testicular carcinoma cell cultures (NTERA-2). Furthermore, cytotoxicity experiments performed on HCT-15 spheroids indicated that [Cu(LCF3)(PPh3)2] possessed remarkable antiproliferative activity, confirming its ability to penetrate the whole spheroid domain and reach the inner hypoxic core.[4] These results indicate Cu(I) complexes with fluorinated or bulky β-diketone ligands as promising candidates for anticancer applications, underscoring the importance of ligand design in improving biological activity
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
) complexes based on sterically hindered β-diketonates with different degrees of fluorination
Full text link: Design, synthesis, and in vitro antitumor properties of Cu(I) and Ag(I) phosphane complexes supported by the anions of sterically hindered β-diketone ligands, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3) featuring trifluoromethyl or methyl groups on the phenyl moieties have been reported. In order to compare the biological effects of substituents on the phenyl moieties, the analogous copper(I) and silver(I) complexes of the anion of the parent 1,3-diphenylpropane-1,3-dione (HLPh) ligand were also synthesized and included in the study. In the syntheses of the Cu(I) and Ag(I) complexes, the phosphane coligands triphenylphosphine (PPh3) and 1,3,5-triaza-7-phosphaadamantane (PTA) were used to stabilize silver and copper in the +1 oxidation state, preventing the metal ion reduction to Ag(0) or oxidation to Cu(II), respectively. X-ray crystal structures of HLCF3 and the metal adducts [Cu(LCF3)(PPh3)2] and [Ag(LPh)(PPh3)2] are also presented. The antitumor properties of both classes of metal complexes were evaluated against a series of human tumor cell lines derived from different solid tumors, by means of both 2D and 3D cell viability studies. They display noteworthy antitumor properties and are more potent than cisplatin in inhibiting cancer cell growth
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