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Coinage metals trinuclear metallocycles: old and new aspects of this class of compounds
Get PDFCoinage metals trinuclear metallocycles: old and new aspects of this class of compounds
Galassi R. a, Oumarou C. S. a, Omary A. M. b, Nesterov V. b, Burini A.a
aSchool of Science and Technology, Chemistry Division, University of Camerino, Via S. Agostino 1, 62032 Camerino; e-mail: [email protected]
b Department of Chemistry, University of North Texas, Denton, 1155 Union Circle, TX 76203, USA; e-mail: [email protected]
Azoles such as imidazoles and pyrazoles are optimal bridging ligands to obtain C,N or N,N trinuclear coinage metals metallocycles. Since past decade till now, few worldwide research groups including us have focused their attention to their synthesis and characterization.[1] Moreover, the photophysical properties[2] the extended network of metallophilic bondings in the supramolecular structure and the pi-acid/pi-base chemistry[3] of these compounds directed the research to theoretical studies bringing to a better interpretation of the experimental behaviors.[4] Here we report the synthesis of new coinage metals metallocycles and their spectroscopic characterizations highlighting points of continuity with the previous analogs and new features for new perspective research lines. As in example, the 1-vinylimidazole resembles the acid-base chemistry of the 1-benzylimidazole gold(I) metallocycle, while substitution in position 4,5 of 1-benzylimidazole with electron-withdrawing group, do not allow the formation of metallocycles with the same synthethic route and mononuclear gold(I) derivatives have been obtained. The nature of the heterocycle and of the substituents, in addition to their position in the azolate ligand defines and tunes the properties of the final products.
References:
1) Galassi, R.; Burini, A.; Omary-Rawanashed, M., Omary, M. A., Comm. Inorg. Chem. 2014, in submission.
2) Rawashdeh-Omary, M. A.; Omary, M. A.; Fackler Jr, J. P, Galassi R., Pietroni, B. R.; Burini, A. J. Am. Chem. Soc 2001, 123; 9689-9691.
3) Burini, A.;. Fackler Jr, J. P; Galassi R., Grant, T. A.. Omary, M. A; Rawashdeh-Omary, M. A.; Pietroni, B. R.; Staples R. J. J. Am. Chem. Soc., 2000; 11264-11265.
4) Galassi, R.; Ricci, S.; Burini, A.; Macchioni, A; Marmottini, F.; Tekarli, S. M.; Nesterov, N.V.; Omary, M. A. Inorg. Chem. 2013, 52, 14124-14137
Computational studies on inhibition of DHFR by gold(I) complexes.
No full textIn spite of increasing activity in the synthesis of gold(I) compounds for pharmacological purposes there is still some divergence of opinion in determining their mechanism of action and their possible molecular target. It is generally accepted that gold compounds act as multi-target drugs and the proposed mechanisms mainly involve enzymes. Some pyrazolyl and imidazolyl gold(I) phosphane complexes synthesized by us have shown anticancer properties and they successfully inhibited seleno-dependent enzymes such as thioredoxine reductase and glutathione peroxidase.[1] DHFR is an important enzyme mainly involved in the synthesis of pyrimidine and thymine basilar for the DNA replication and hence the cell proliferation.[2] Despite its fundamental importance in the cell’s metabolism this enzyme has never been tested as molecular target for gold(I) compounds. Methotrexate is a well-known inhibitor of DHFR and methotrexate and gold(I) complexes have a common history in the treatment of certain diseases such as psoriasis, rheumatoid arthritis and other autoimmune diseases. As a prosecution of an ongoing study about the action of gold(I) azolate phosphane complexes on the regard of the inhibition of DHFR, computational molecular docking studies have been led. They suggest that the compound 4,5-dicyanoimidazolate-AuPPh3 binds to a site of DHFR located in proximity of the nicotinamide moiety of NADP+ (Figure). Moreover, the studies suggest that the site of 4,5-dicyanoimidazolate-AuPPh3 partially overlaps with the methotrexate, indicating that the binding of the two molecules may be mutually exclusive. These results support our kinetic data showing an interaction between pyrazolyl and imidazolyl gold(I) phosphane complexes and the catalytic site of DHFR.
Figure. DHFR in complex with 4,5-ImCl2N-AuPPh3 and NADP+
References
[1] R. Galassi, A. Burini, S. Ricci, M. Pellei, M. P. Rigobello, A. Citta, A. Dolmella, V. Gandin, C Marzano. Dalton Trans., 2012, 41, 5307
[2] J.R. Schnell, H.J. Dyson, P.E. Wright. Annu. Rev. Biophys. Biomol. Struct., 2004, 33, 119–140
Supramolecular Chemistry and photophysical Properties of a New Gold (I) Cyclic Trinuclear Complex, [Au(μ-C2,N3-1-vinylimidazole)]3
Get PDFSupramolecular Chemistry and photophysical Properties of a New Gold (I) Cyclic Trinuclear Complex, [Au(μ-C2,N3-1-vinylimidazole)]3
R. Galassia, A. Burinia, C. S. Oumaroua, V. N. Nesterov b, M. A. Omary b.
a Dipartimento di Scienze Chimica, Università di Camerino, Via Sant Agostino, 1, 62032 Camerino, Italia
b Department of Chemistry, University of North Texas, Denton, TX 76203, USA
email: [email protected]
In the past years several cyclic trinuclear complexes (CTC’s) have been synthetized and characterized on the basis of the capacity of d10 transition metal ions to give bicoordinated linear compounds. This intriguing class of compounds display pi-acid/ pi-base properties that can be finely tuned by: the nature of the metal, the substituents on the ligand or the ligand itself. [1] These complexes are attractive building blocks to obtain supramolecular compounds showing interesting photopysical properties [2] or heterobimetallic cyclic trinuclear complexes with potential use in mixed-metal catalysis [3]. Here we report the synthesis of a novel gold (I) CTC, [Au(μ-C2,N3-1-vinylimidazole)]3, and the study of some photophysical properties of its supramolecular derivatives obtained by the intercalation of metal ions in between the metallocycles.
[1] S.M. Terkali, T.R. Cundari, M.A. Omary, J. Am. Chem. Soc. 2008, 130, 1669
[2] a) A. Burini, R. Bravi, J. P. Fackler Jr, Galassi R., T. A. Grant, M. A. Omary, B. R. Pietroni, R. J. Staples . Inorg. Chem. 2000, 39; 3158.b) Burini A, Fackler J. P, JR, Galassi R., Grant T. A, Omary M. A, Rawashdeh-Omary M. A, Pietroni B. R, Staples R.J. J. Am. Chem. Soc. 2000, 122; 11264.
[3] A. Mohamed, R. Galassi, F. Papa, A. Burini, J.P. Fackler , Jr. Inorg. Chem. 2006, 45, 7770-7776
[5] R. Galassi, S. Ricci, A. Burini, A. Macchioni, L. Rocchiagiani, F. Marmottini, S.M. Terkali, V.N. Nesterov, M.A. Omary, Inorg. Chem. 2013, 52, 14124-1413
Solventless VOC chemisorption by silver metallocycles
No full textSolventless VOC chemisorption by silver metallocycles
Oumarou C. S.a, Tekarli S.,b Nesterov V.,b Omary M. A.,b Burini A.,a Galassi R.,a
aSchool of Science and Technology, Chemistry Division, University of Camerino, Via S. Agostino 1, 62032 Camerino; e-mail: [email protected]
b Department of Chemistry, University of North Texas, Denton, TX 76203, USA
Prior work has focused on detection/sensing aspects of VOCs,[1] this work proposes a method for their simultaneous filtration and removal through their strong chemisorption to a silver(I) metallocyclic trimer.[2] A solid cyclotrimer can quantitatively remove entire molar integers of VOCs (1-3 equivalents of VOCs per mole of the nitrated trimer) from the vapor phase in a solventless “green” chemical process, which is unprecedented for this class of cyclic d10 complexes.
Figure 1. Illustration of quadrupole-dipole interactions involving the [Ag(μ-Pz-2CF3)]3 or [Ag(3,5-(NO2)2pz)]3 trimers and acetonitrile using M06/CEP-31G(d). MEP surfaces are plotted in two manners, either mapped on electron density surfaces (rainbow plots with the color scale shown; isodensity = 0.0004) or positive (blue) and negative (red) regions in space (range = ± 2.2 a. u.; isodensity = 0.02)
[1] Yaghi et al., PNAS 2008, 105, 11623
[2] R. Galassi, S. Ricci, A. Burini, A. Macchioni, L. Rocchigiani, F. Marmottini, S. Tekarli, V. Nesterov, M. A. Omary, J. Am. Chem. Soc., 2013, submitted
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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