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THE ENDLESS POSSIBILITIES OF RUTHENIUM DMSO PRECURSORS IN MODERN COORDINATION CHEMISTRY: FROM NOVEL METALLACYCLES OF PORPHYRINS TO NEW ROUTES TO HETEROLEPTIC POLYPYRIDYL COMPOUNDS
Full text linkLa ricerca svolta durante questo dottorato di ricerca. e riportata in questa Tesi è incentrata sulla progettazione, preparazione e caratterizzazione di diversi sistemi porfirinici supramolecolari, sia metallaciclici che polimerici.
Il Capitolo 1 contiene un'introduzione generale sul ruolo chiave delle porfirine come building block funzionali e strutturali per l'assemblaggio di strutture supramolecolari discrete, insieme ai principali concetti del metal-mediated assembly.
Il Capitolo 2 è incentrato sullo studio della reattività dei due stereoisomeri [cis,cis,cisRuCl2(CO)2(dmso-O)(dmso-S)] e [cis,cis,trans-RuCl2(CO)2(dmso-S)2] verso la 4′cisDPyP. I complessi sono stati prima testati sul legante modello 4′MPyP e successivamente utilizzando la 4′cisDPyP ottenendo, oltre al già noto metallaciclo porfirinico 2+2 [trans,cis,cisRuCl2(CO)2(4′cisDPyP)]2, anche i due relativi stereoisomeri chirali [{trans,cis,cisRuCl2(CO)2} 4′cisDPyP)2{cis,cis,cis-RuCl2(CO)2}] e [cis,cis,cis-RuCl2(CO)2(4′cisDPyP)], in cui il frammento {cis,cis,cis-RuCl2(CO)2} può avere chiralità C o A.
Nel Capitolo 3 viene descritta una strategia sintetica che permette di ottenere metallacicli porfirinici più estesi. Questa strategia ha permesso di ottenere sistemi triporfirinici, che, dopo metallazione, potrebbero portare a formare assemblati supramolecolari più stabili. Inoltre, sono anche stati sintetizzati metallacicli eterolettici contenenti porfirine diverse (i.e. 3 ′ e 4′-piridilporfirine) e aventi diversi tipi di geometrie (vaso, scala, zig-zag). Durante i miei tre anni di dottorato di ricerca sono stato anche coinvolto in altri progetti che coinvolgono complessi Ru (II)-dmso, in particolare:
Nel Capitolo 4 è stato dimostrato che la rutenazione di una porfirina può essere eseguita in condizioni relativamente blande utilizzando il complesso monocarbonilico di Ru(II) [Ru(CO)(dmso)5][PF6]2 che - oltre al CO - presenta esclusivamente leganti labili. Questo è solo il secondo esempio di utilizzo di un complesso carbonilico di Ru(II) per la rutenazione di una porfirina, dopo il primo riportato quasi 50 anni fa e poi dimenticato. Da un punto di vista pratico, si mostra il sorprendente effetto dell'acido propionico come solvente per eseguire la rutenazione di porfirine modello neutre e anioniche utilizzano il cluster Ru3(CO)12.
Le Ru(CO)-porfirine sono state poi sfruttate, nel Capitolo 5, per preparare network polimerici di Ru/Zn porfirine. In particolare, è stato dimostrato che il PTA (1,3,5-triaza-7-fosfadamamantano) si comporta come un legante ortogonale tra Ru (II) e Zn (II), poiché si lega selettivamente attraverso l'atomo di P al rutenio e attraverso uno o più degli atomi di N allo zinco. Questa proprietà del PTA è stata sfruttata per preparare due addotti porfirinici monomerici aventi un PTA legato assialmente,[Ru(TPP)(PTA-kP)2] e [Zn(TPP)(PTA-kN)]. Successivamente, sono stati preparati una serie di
network polimerici di Ru /Zn porfirine eterobimetallici - e due sistemi molecolari discreti - mediati da PTA in cui entrambi i metalli risiedono all'interno di uno dei centri porfirinici, o un metallo appartiene a una porfirina, o Ru (TPP) o Zn (TPP), e l'altro a un complesso o sale dell’altro metallo. Il Capitolo 6 riporta una nuova strategia a stadi, per la sintesi di composti polipiridilici bis-eterolettici di Ru (II) di formula generale [Ru (chel)2(chel′))]2+, dove chel è un legante chelante dimminico, a partire da precursori di Ru(II) cis bloccati. Questi sono stati sintetizzati sostituendo i due cloruri, o un cloruro e un dmso, dal complesso [cis-RuCl2(dmso)4] con un anione chelante inerte (O – O) (malonato, ossalato, acetilacetonato). Questo permette di avere un maggior controllo nella coordinazione del primo legante (chel), diminuendo la formazione di miscele stereoisomeriche. La sensibilità all’ambiente acido dell’anione chelante ne permette la sostituzione con un secondo legante anche a temperatura ambiente.The research carried out during this Ph.D. project and reported in this Thesis is focused on the design, preparation and characterization of different supramolecular porphyrin systems, both metallacyclic and polymeric.
Chapter 1 contains a general introduction on the key role of porphyrins as functional and structural building units for the assembly of artificial discrete supramolecular structures, together with the main designing concepts of the metal-mediated assembly.
Chapter 2 is focused on the investigation of the reactivity of the two stereoisomers [cis,cis,cisRuCl2(CO)2(dmso-O)(dmso-S)] and [cis,cis,trans-RuCl2(CO)2(dmso-S)2] towards 4′cisDPyP. The complexes were first tested toward the model ligand 4′MPyP and then 4′cisDPyP obtaining, besides the already known 2+2 metallacycle of porphyrins [trans,cis,cis-RuCl2(CO)2(4′cisDPyP)]2, the chiral stereoisomeric metallacycles [{trans,cis,cis-RuCl2(CO)2}(4′cisDPyP)2{cis,cis,cis-RuCl2(CO)2}] and [cis,cis,cis-RuCl2(CO)2(4′cisDPyP)]2, in which the chiral {cis,cis,cis-RuCl2(CO)2} fragment has
either a C or A handedness.
In Chapter 3 a synthetic strategy for the expansion of porphyrin metallacycles is described. This strategy afforded triporphyrin arrays that, after metalation, might lead to more stable supramolecular assemblies. Furthermore, we also synthesized heteroleptic metallacycles containing different porphyrins (i.e. 3′ and 4′-pyridylporphyrins) that have unprecedented geometries (i.e. vase, ladder,zig-zag).
During my three years of Ph.D. I have also been involved in other projects involving Ru(II)-dmso complexes, in particular:
In Chapter 4 we demonstrate that ruthenation of a porphyrin can be performed under relatively mild conditions using the Ru(II) monocarbonyl complex [Ru(CO)(dmso)5][PF6]2 that – besides CO –features exclusively labile dmso ligands. Even though this finding might seem trivial, it is only the second example that uses a Ru(II) carbonyl for porphyrin ruthenation, the first one having been reported almost 50 years ago and then neglected. From a practical point of view, we show the
spectacular effect of propionic acid as solvent for performing the ruthenation of neutral and anionic model porphyrins with Ru3(CO)12.
The Ru(CO)-porphyrins were then exploited, in Chapter 5 to prepare Ru/Zn porphyrin polymeric networks. In particular we demonstrate that PTA (1,3,5-triaza-7-phosphaadamantane) behaves as an orthogonal ligand between Ru(II) and Zn(II), since it selectively binds through the P atom to ruthenium and through one or more of the N atoms to zinc. This property of PTA was exploited for preparing the two monomeric porphyrin adducts with axially bound PTA, [Ru(TPP)(PTA-kP)2] and
[Zn(TPP)(PTA-kN)]. Next, we prepared a number of heterobimetallic Ru/Zn porphyrin polymeric networks — and two discrete molecular systems — mediated by P,N-bridging PTA in which either both metals reside inside a porphyrin core, or one metal belongs to a porphyrin, either Ru(TPP) or Zn(TPP), and the other to a complex or salt of the complementary metal. Chapter 6 reports a new two-step strategy for the synthesis of bis-heteroleptic Ru(II) polypyridyl compounds of general formula [Ru(chel)2(chel′)]2+, where chel is a chelating dimmine ligand, starting from cis-locked Ru(II) precursors. These were synthesized by replacing either the two chlorides, or a chloride and a dmso, from the [cis-RuCl2(dmso)4] complex with an inert chelating anion (O–O) (i.e. malonate, oxalate, acetylacetonate). This allowed us to have more control in the coordination of the first ligand (chel), decreasing the formation of stereoisomeric mixtures. The acid-sensitive nature of the chelating anion allows its acid-assisted substitution with the second ligand chel′ even at room
temperature
The Insertion of Ruthenium into Porphyrins Revisited and Improved: Proof of Concept Results with a Ruthenium(II) Monocarbonyl Compound, and the Spectacular Effect of Propionic Acid
Full text linkThis contribution, that readdresses the insertion of the Ru(II)–CO fragment into model porphyrins (i.e. ruthenation), has a Janus character, with one speculative and one practical side. As a proof of concept we demonstrate that ruthenation of a porphyrin can be performed under relatively mild conditions using the Ru(II) monocarbonyl complex [Ru(CO)(dmso)5][PF6]2 that – besides CO – features exclusively labile dmso ligands. Even though this finding might seem trivial, it is only the second example that uses a Ru(II) carbonyl for porphyrin ruthenation, the first one having been reported almost 50 years ago and then neglected. From a practical point of view, we show the spectacular effect of propionic acid as solvent for performing the ruthenation of neutral and anionic model porphyrins with Ru3(CO)12 (1). This process turned out to be extremely efficient and advantageous in terms of both reaction rates and yields (e.g. 100% ruthenation of TPP in 30 min at 140°C) compared to the procedures described in the literature
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Investigating the reactivity of neutral water-soluble Ru(ii)–PTA carbonyls towards the model imine ligands pyridine and 2,2′-bipyridine
No full textAs a continuation of our strategy for preparing new Ru(II) precursors to be exploited as building blocks in the construction of metal-mediated supramolecular assemblies with improved solubility in water, here we describe the reactivity of selected neutral Ru(II)–PTA carbonyls (PTA = 1,3,5-triaza-7-phosphaadamantane) towards the model imine ligands pyridine (py) and 2,2′-bipyridine (bpy) and the preparation and characterization of several neutral and cationic water-soluble derivatives: trans,trans,trans-[RuCl2(CO)(py)(PTA)2] (7), cis,cis,trans-[RuCl2(CO)2(py)(PTA)] (9), cis,trans-[Ru(bpy)Cl(CO)(PTA)2]Cl (10), mer-[Ru(bpy)(CO)(PTA)3](Cl)2 (12), cis,trans-[Ru(bpy)(CO)2Cl(PTA)]Cl (13), cis,trans-[Ru(bpy)(CO)2(PTA)2](NO3)2 (14NO3). In addition, we found that light-induced isomerization in some bpy compounds could be induced. The following species, either side-products isolated in low yield or compounds obtained exclusively in solution, were also unambiguously identified: cis,cis,trans-[RuCl2(CO)(py)(PTA)2] (8), trans-[RuCl2(bpy)(CO)(PTA)] (11), cis,cis-[Ru(bpy)Cl(CO)(PTA)2]Cl (15) and cis,cis-[Ru(bpy)(CO)2Cl(PTA)]Cl (16). The X-ray structures of 7, 11·H2O, and 12·7H2O are also reported. All compounds are new and – with few exceptions – show a good solubility in water
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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