Relative Rates of Metal-Free Azide-Alkyne Cycloadditions: Tunability over 3 Orders of Magnitude.

The thermal (3 + 2) dipolar azide-alkyne cycloaddition, proceeding without copper or strained alkynes, is an underutilized ligation with potential applications in materials, bioorganic, and synthetic chemistry. Herein, we investigate the effects of alkyne substitution on the rate of this reaction, both experimentally and computationally. Electron-withdrawing groups accelerate the reaction, providing a range of relative rates from 1.0 to 2100 between the slowest and fastest alkynes studied. Unexpectedly, aryl groups conjugated to the alkyne significantly retard the reaction rate. In contrast, a sulfonyl, ester-substituted alkyne is reactive enough that it couples with an azide at room temperature in a few hours. This reactivity scale should provide a guide to those who wish to use this ligation under mild conditions

A new family of high nuclearity CoII/DyIII coordination clusters possessing robust and unseen topologies

Mixing Co(NO3)2·6H2O/Dy(NO3)3·6H2O/(E)-4-(2-hydroxy-3-methoxybenzylideneamino)-2,3-dimethyl-1-phenyl-1,2-dihydropyrazol-5-one (HL)/pivalic acid/Et3N in various solvents results in the synthesis of seven compounds formulated as [CoII2DyIII2(μ3-MeO)2(L)2(piv)4(NO3)2] (3), [CoIIDyIII3(μ3-MeO)2(μ2-MeO)2(L)2(piv)2(NO3)3]·2(CH3OH) (4·2CH3OH), 2[CoII4DyIII4(μ2-O)2(μ3-OH)4(L)4(piv)8][CoII2DyIII5(μ3-OH)6(L)2(piv)8(NO3)4] (5), [CoII4DyIII4(μ2-O)2(μ3-OH)4(L)4(piv)8]·2(CH3CN) (6·2CH3CN), [CoII2DyIII5(μ3-OH)6(L)2(piv)8(NO3)4]·4(CH3CN) (7·4CH3CN), [CoII2DyIII2(μ3-OH)2(L)2(piv)2(NO3)2(EtOH)2(H2O)2](NO3)2·(EtOH) (8·EtOH) and [CoII4DyIII4(μ2-O)2(μ3-OH)4(L)4(piv)8] (9) with robust and unseen topologies. These show that the temperature and reaction time influence the formation of the final product. Preliminary magnetic studies, performed for 6 and 7 in the temperature range 2-300 K, are indicative of Single Molecule Magnet (SMM) behaviour. Moreover, analysis of the catalytic properties of compound 3 as an efficient catalyst for the synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary amines has been carried out

King’s Touch:: The establishment of the relevant healing practice and its significance in the legitimizing of the English and French monarchies during Late Middle Ages, from the 11th to the dawn of 14th century

Η πίστη πως το άγγιγμα του μονάρχη μπορούσε να θεραπεύσει ορισμένες θανατηφόρες ασθένειες εμφανίστηκε στα βασίλεια της Αγγλίας και της Γαλλίας κατά τη διάρκεια του Ώριμου Μεσαίωνα. Ως την αυγή του Ύστερου Μεσαίωνα (αρχές 14ου αιώνα) τόσο το αγγλικό όσο και το γαλλικό στέμμα είχε προσδώσει στους βασιλεύοντες μονάρχες την κληρονομική ιδιότητα του θαυματουργού που ειδικευόταν στη θεραπεία της scrofula. Σε αμφότερα τα βασίλεια η χριστομιμητική τελετή του βασιλικού αγγίγματος θεσμοθετήθηκε από ιδιαίτερα ευσεβείς μονάρχες, ενώ δεν ήταν λίγοι οι βασιλείς που δεν έδωσαν έμφαση στην απεικόνισή τους ως θεραπευτές. Η παρούσα μελέτη επιχειρεί να ρίξει φως, αφενός στις πολιτικές, πολιτιστικές και πνευματικές συνθήκες, οι οποίες συνεισέφεραν στην ανάδυση, την τέλεση και τη θεσμοθέτηση του θεραπευτικού αγγίγματος, αφετέρου στη θέση που καταλάμβανε η εικόνα του «βασιλικού θεραπευτή» στη συγκρότηση της ευρύτερης «ιερότητας» των δύο μοναρχιών. Συνεπώς, η ακριβής αποτίμηση της τελετής επιτάσσει την καταφυγή σε όλες τις, γνωστές, διασωθείσες πρωτογενείς πηγές αναφέρονται στην πρακτική του αγγίγματος.The idea that the monarch’s touch could cure certain deadly diseases appeared in the kingdoms of England and France during the High Middle-Ages. Until the dawn of the Late Middle Ages (early 14th century) both the English and the French Crown had bestowed their reigning monarchs with the hereditary ability of a wonder-maker who specialized in the cure of scrofula. In both kingdoms, the christo-memetic ritual of royal touch was institutionalized by particularly pious rulers. On the other hand, not all kings emphasized their depiction as healers. This study attempts to shed light on the political, cultural, and spiritual conditions which contributed to the emergence, practice, and institutionalization of the healing touch. Furthermore, it highlights the significance of the «royal healer’s» image in the construction of the two monarchies’ broader «sacrality». For the consistent evaluation of the ritual the use of the available and known primary sources, referring to the practice of touching, is pivotal

Συγκρότηση Κράτους και Εβραϊκές Κοινότητες στα Βασίλεια της Αγγλίας και της Γαλλίας κατά τον Ώριμο Μεσαίωνα (11ος-14ος αιώνας).

Στην παρούσα μεταπτυχιακή διατριβή εξετάζεται η διαδικασία συγκρότησης κράτους στα βασίλεια της Αγγλίας και της Γαλλίας κατά τον Ώριμο Μεσαίωνα σε συνδυασμό με την επίδραση που αυτή άσκησε στις εβραϊκές κοινότητες των δύο βασιλείων. Πρόκειται για μια μακροϊστορική μελέτη στην οποία διερευνάται η περίοδος από την εποχή της «φεουδαλικής επανάστασης», που εκδηλώθηκε στη Γαλλία μετά την αποσύνθεση της αυτοκρατορίας των Καρολίδων τον 10ο αιώνα και στην Αγγλία μετά τη νορμανδική κατάκτηση του 1066, και φτάνει ως τις αρχές του 14ου αιώνα και τις βασιλείες του Φιλίππου Δ΄ και του Εδουάρδου Α΄ αντίστοιχα. Ειδικότερα, παρουσιάζεται η μακραίωνη διαδικασία της κρατικής διαμόρφωσης μέσω της εξέτασης των κυβερνητικών και πολιτικών καινοτομιών που εισήχθησαν κατά τη διάρκεια των βασιλειών δεκαέξι μοναρχών (επτά Γάλλων και εννέα Άγγλων). Υποστηρίζεται ότι μέχρι τις αρχές του 14ου αιώνα τα βασίλεια της Γαλλίας και της Αγγλίας ανέπτυξαν τα δύο πιο διακεκριμένα μοντέλα ευρωπαϊκού κράτους. Ταυτόχρονα, αποκαλύπτεται πως η κρατική μετεξέλιξη διαδραμάτισε πρωταρχικό ρόλο στην αντιμετώπιση των Εβραίων από τις κυβερνητικές αρχές καθώς και στη διαμόρφωση του εβραϊκού status από την εποχή της εβραϊκής εγκατάστασης έως την απέλασή τους από τα δύο βασίλεια.The subject of this master’s thesis is the analysis of the state-building process in the kingdoms of England and France during the High Middle Ages and the impact of this process on the Jewish communities of the aforesaid kingdoms. It is a macrohistorical study, stretching from the era of “feudal revolution”, which manifested in France after the disintegration of the Carolingian Empire in the 10th century and in England after the norman conquest of 1066, to the beginning of the 14th century and the reigns of Philip IV and Edward I respectively. More specifically, the long procedure of state forming is presented by examining the governmental and political innovations which took place during the reigns of sixteen monarchs (seven French and nine English). It will be argued that, until the beginning of the 14th century, the kingdoms of France and England developed the two most prominent models of the European state. On the same time, it is asserted that state transformation played a paramount role in the treatment of Jews by governmental authorities as well as the formation of Jewish status, from the time of Jewish settlement until their expulsion from the two kingdoms

Probing the magnetic and magneto-optical properties of a radical-bridged Tb4 single-molecule magnet

Abstract Reaction of the 1,2,4,5-tetrazine (tz˙−) radical and {Cp*2Tb}+ has yielded a tetranuclear radical-bridged TbIII single-molecule magnet. The strong Ln–radical coupling and the electronic differences of the TbIII ions in [(Cp*2Tb)4(tz˙−)4]·3C6H6 (1) are probed via magnetic, magneto-optical and computational studies.Abstract Reaction of the 1,2,4,5-tetrazine (tz˙−) radical and {Cp*2Tb}+ has yielded a tetranuclear radical-bridged TbIII single-molecule magnet. The strong Ln–radical coupling and the electronic differences of the TbIII ions in [(Cp*2Tb)4(tz˙−)4]·3C6H6 (1) are probed via magnetic, magneto-optical and computational studies

Radical Bridged Ln₄ Metallocene Complexes with Strong Magnetic Coupling and Large Coercive Field

AbstractInducing magnetic coupling between 4f elements is an ongoing challenge. To overcome this formidable difficulty, we incorporate highly delocalized tetrazinyl radicals, which strongly couple with f-block metallocenes to form discrete tetranuclear complexes. Synthesis, structure, magnetic properties of two tetranuclear [(Cp*₂Ln)₄(tz•)₄]·3(C₆H₆) (Cp* = pentamethylcyclopentadienyl; tz = 1,2,4,5-tetrazine; Ln = Dy, Gd) complexes are reported. An in-depth examination of their magnetic properties through magnetic susceptibility measurements, as well as computational studies, support a highly sought-after radical-induced “giant-spin” model. Strong exchange interactions between the LnIII ions and tz• radicals lead to a strong magnet-like behaviour in this molecular magnet with a giant coercive field of 30 kOe.Abstract Inducing magnetic coupling between 4f elements is an ongoing challenge. To overcome this formidable difficulty, we incorporate highly delocalized tetrazinyl radicals, which strongly couple with f-block metallocenes to form discrete tetranuclear complexes. Synthesis, structure, magnetic properties of two tetranuclear [(Cp*₂Ln)₄(tz•)₄]·3(C₆H₆) (Cp* = pentamethylcyclopentadienyl; tz = 1,2,4,5-tetrazine; Ln = Dy, Gd) complexes are reported. An in-depth examination of their magnetic properties through magnetic susceptibility measurements, as well as computational studies, support a highly sought-after radical-induced “giant-spin” model. Strong exchange interactions between the LnIII ions and tz• radicals lead to a strong magnet-like behaviour in this molecular magnet with a giant coercive field of 30 kOe

A trivalent 4f complex with two bis-silylamide ligands displaying slow magnetic relaxation

Abstract The best-performing single-molecule magnets (SMMs) have historically relied on pseudoaxial ligands delocalized across several coordinated atoms. This coordination environment has been found to elicit strong magnetic anisotropy, but lanthanide-based SMMs with low coordination numbers have remained synthetically elusive species. Here we report a cationic 4f complex bearing only two bis-silylamide ligands, Yb(III)[{N(SiMePh2)2}2][Al{OC(CF3)3}4], which exhibits slow relaxation of its magnetization. The combination of the bulky silylamide ligands and weakly coordinating [Al{OC(CF3)3}4]− anion provides a sterically hindered environment that suitably stabilizes the pseudotrigonal geometry necessary to elicit strong ground-state magnetic anisotropy. The resolution of the mJ states by luminescence spectroscopy is supported by ab initio calculations, which show a large ground-state splitting of approximately 1,850 cm−1. These results provide a facile route to access a bis-silylamido Yb(III) complex, and further underline the desirability of axially coordinated ligands with well-localized charges for high-performing SMMs.Abstract The best-performing single-molecule magnets (SMMs) have historically relied on pseudoaxial ligands delocalized across several coordinated atoms. This coordination environment has been found to elicit strong magnetic anisotropy, but lanthanide-based SMMs with low coordination numbers have remained synthetically elusive species. Here we report a cationic 4f complex bearing only two bis-silylamide ligands, Yb(III)[{N(SiMePh2)2}2][Al{OC(CF3)3}4], which exhibits slow relaxation of its magnetization. The combination of the bulky silylamide ligands and weakly coordinating [Al{OC(CF3)3}4]− anion provides a sterically hindered environment that suitably stabilizes the pseudotrigonal geometry necessary to elicit strong ground-state magnetic anisotropy. The resolution of the mJ states by luminescence spectroscopy is supported by ab initio calculations, which show a large ground-state splitting of approximately 1,850 cm−1. These results provide a facile route to access a bis-silylamido Yb(III) complex, and further underline the desirability of axially coordinated ligands with well-localized charges for high-performing SMMs

Tunable Energy-Transfer Process in Heterometallic MOF Materials Based on 2,6-Naphthalenedicarboxylate: Solid-State Lighting and Near-Infrared Luminescence Thermometry

Trivalent lanthanide ions (Ln3+) are used to prepare a plethora of coordination compounds, with metal-organic frameworks (MOFs) being among the most sought-after in recent years. The porosity of Ln-MOFs is often complemented by the luminescence imparted by the metal centers, making them attractive multifunctional materials. Here, we report a class of three-dimensional (3D) MOFs obtained from a solvothermal reaction between 2,6-naphthalenedicarboxylic acid (H2NDC) and lanthanide chlorides, yielding three types of compounds depending on the chosen lanthanide: [LnCl(NDC)(DMF)] for Ln3+ = La3+, Ce3+, Pr3+, Nd3+, Sm3+ (type 1), [Eu(NDC)1.5(DMF)]·0.5DMF (type 2), and [Ln2(NDC)3(DMF)2] for Ln3+ = Tb3+, Dy3+, Y3+, Er3+, Yb3+ (type 3). Photoluminescent properties of selected phases were explored at room temperature. The luminescence thermometry capability of Yb3+-doped Nd-MOF was fully investigated in the 15-300 K temperature range under 365 and 808 nm excitation. To describe the optical behavior of the isolated MOFs, we introduce the total energy-transfer balance model. Therein, the sum of energy-transfer rates is considered along with its dependence on the temperature - the sign, magnitude, and variation of this parameter - permitting to afford a thorough interpretation of the observed behavior of the luminescent species of all materials presented here. The combination of novel theoretical and experimental studies presented herein to describe energy-transfer processes in luminescent materials can pave the way toward the design of MOF-based chemical and physical sensors working in an optical range of interest for biomedical applications.Fil: Gomez, Germán Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Marin, Riccardo. University of Ottawa; CanadáFil: Carneiro Neto, Albano N.. Universidade de Aveiro; PortugalFil: Botas, Alexandre M. P.. Universidade de Aveiro; PortugalFil: Ovens, Jeffrey. University of Ottawa; CanadáFil: Kitos, Alexandros A.. University of Ottawa; CanadáFil: Bernini, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Carlos, Luís D.. Universidade de Aveiro; PortugalFil: Soler Illia, Galo Juan de Avila Arturo. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Murugesu, Muralee. University of Ottawa; Canad

Fibrous TiO2 Alternatives for Semiconductor-Based Catalysts for Photocatalytic Water Remediation Involving Organic Contaminants

Water decontamination remains a challenge in several developed and developing countries. Affordable and efficient approaches are needed urgently. In this scenario, heterogeneous photocatalysts appear as one of the most promising alternatives. This justifies the extensive attention that semiconductors, such as TiO2, have gained over the last decades. Several studies have evaluated their efficiency for environmental applications; however, most of these tests rely on the use of powder materials that have minimal to no applicability for large-scale applications. In this work, we investigated three fibrous TiO2 photocatalysts, TiO2 nanofibers (TNF), TiO2 on glass wool (TGW), and TiO2 in glass fiber filters (TGF). All materials have macroscopic structures that can be easily separated from solutions or that can work as fixed beds under flow conditions. We evaluated and compared their ability to bleach a surrogate dye molecule, crocin, under batch and flow conditions. Using black light (UVA/visible), our catalysts were able to bleach a minimum of 80% of the dye in batch experiments. Under continuous flow experiments, all catalysts could decrease dye absorption under shorter irradiation times: TGF, TNF, and TGW could, respectively, bleach 15, 18, and 43% of the dye with irradiation times as short as 35 s. Catalyst comparison was based on the selection of physical and chemical criteria relevant for application on water remediation. Their relative performance was ranked and applied in a radar plot. The features evaluated here had two distinct groups, chemical performance, which related to the dye degradation, and mechanical properties, which described their applicability in different systems. This comparative analysis gives insights into the selection of the right flow-compatible photocatalyst for water remediation