874 research outputs found
Thermodynamic Insights on a Bistable Acid–Base Switchable Molecular Shuttle with Strongly Shifted Co-conformational Equilibria
No full textBistable [2]rotaxanes in which the affinities of the two stations can be reversed form the basis of molecular shuttles. Gaining quantitative information on such rotaxanes in which the ring distribution between the two stations is largely nonsymmetric has proven to be very challenging. Herein, we report on two independent experimental methodologies, based on luminescence lifetime measurements and acid–base titrations, to determine the relative populations of the two co‐conformations of a [2]rotaxane. The assays yield convergent results and are sensitive enough to measure an equilibrium constant (K≈4000) out of reach for NMR spectroscopy. We also estimate the ring distribution constant in the switched (deprotonated) state (K′99.92 %). Finally, our results show that the pKa of the pH‐responsive station depends on the ring affinity of the pH‐insensitive station, an observation that paves the way for the design of new artificial allosteric systems
Metal-Controlled Assembly and Selectivity of a Urea-Based Anion Receptor
No full textThe terdentate ligand 3 (LH, 2-formylpyridine 4-thiosemicarbazone) forms with FeII and NiII 2:1 complexes of octahedral geometry of formula [MII(LH)2]2+. X-ray diffraction studies have shown that in both complexes the thiourea moieties of the coordinated thiosemicarbazones are exposed to the outside and are prone to establish hydrogen-bonding bifurcate interactions with oxoanions. However, spectrophotometric studies in CHCl3 soln. have shown that only the poorly basic NO3- ion is able to form authentic hydrogen-bond complexes with thiourea subunits, whereas all the other investigated anions (CH3COO-, NO2-, F-) induce deprotonation of the N-H fragment. The extreme enhancement of the thiourea acidity is based on the coordinative interaction of the sulfur atom with the metal, which stabilizes the thiolate form, and it is much higher than that exerted by any other covalently linked electron-withdrawing substituent, for example, -NO2
Light-driven molecular machines based on ruthenium(II) polypyridine complexes: Strategies and recent advances
No full textMulticomponent molecular systems that exhibit large amplitude movements controlled by external inputs – namely, molecular machines – are extensively investigated both for their basic science interest and for their potential applications in technology and medicine. Light is a convenient stimulus to operate molecular machines because it can provide both an energy supply to feed their motion and an analytical signal to monitor their state. Research in the past two decades has shown that the unique and highly tunable structural, photophysical, photochemical and redox properties of Ru(II) polypyridine complexes are advantageous tools for implementing a light-induced response in molecular devices and machines. Here we describe the latest progresses in the realization of artificial nanoscale machines that use such metal complexes to process light signals. We will show the level of creativity and sophistication reached in this research area by describing a few selected examples
Redox Driven Intramolecular Anion Translocation Between a Metal Centre and a H bond Donating Compartment
No full textAbstract: Dicationic ligands incorporating
two 2,2’-bipyridine units and two
imidazolium moieties, [1]2+ and [2]2+,
form stable chelate complexes with
CuII and CuI in acetonitrile solution.
Each CuII complex binds two X ions
according to two stepwise equilibria,
the first involving the CuII centre and
the second involving the bis-imidazolium
compartment. CuI complexes are
able to host only one NO3 ion in the
bis-imidazolium cavity, while other
anions induce demetallation. Thus, in
the presence of one equivalent of
NO3, the CuII/CuI redox change
makes the anion translocate quickly
and reversibly from one binding site to
the other within the [CuII,I(1)]4+/3+
system, as demonstrated by cyclic voltammetry
and controlled-potential
electrolysis experiments
Scaling up qualitative data: with Professor Ken Benoit
No full textProfessor Benoit is the Principal Investigator in an ERC funded project QUANTESS developing innovative methods for the quantitative analysis of textual data in the social sciences. He is the co-author with Paul Nulty of the R software package for text analysis “quanteda”, and working on a book Quantitative Text Analysis Using R covering methods for managing, processing, and analysing textual data using the R programming language. He has taught quantitative text analysis extensively and has published research in this area targeting both methodology and political science applications
A Metal-Based Trisimidazolium Cage that Provides Six C-H Hydrogen-Bond-Donor Fragments and Includes Anions
No full textSheltering under the roof: A trisimidazolium cage is capped with a {FeII(bpy)3}2+ subunit to produce a receptor that can bind small anions (bpy=2,2′-bipyridine). Rodlike “pseudohalide” (N3−, NCO−, and NCS−) and spherical halide (Cl−, Br−, and I−) anions accept hydrogen bonds from CH fragments in the receptor cavity. The N3− ion forms the most stable inclusion compound (see structure; Fe red, C light blue, H white, N dark blue)
Photoinduced Electron Transfer Involving a Naphthalimide Chromophore in Switchable and Flexible [2]Rotaxanes
No full textThe interlocking of ring and axle molecular components in rotaxanes provides a way to combine chromophoric, electron-donor and electron-acceptor moieties in the same molecular entity, in order to reproduce the features of photosynthetic reaction centers. To this aim, the photoinduced electron transfer processes involving a 1,8-naphthalimide chromophore embedded in several rotaxane-based dyads were investigated by steady-state and time-resolved absorption and luminescence spectroscopic experiments in the 300 fs-10 ns time window. Different rotaxanes built around the dialkylammonium / dibenzo[24]crown-8 ether supramolecular motif were designed and synthesized to decipher the relevance of key structural factors, such as the chemical deactivation of the ammonium-crown ether recognition, the presence of a secondary site for the ring along the axle, and the covalent functionalization of the macrocycle with a phenothiazine electron donor. Indeed, the conformational freedom of these compounds gives rise to a rich dynamic behavior induced by light, and may provide opportunities for investigating and understanding phenomena that take place in complex (bio)molecular architectures
Thesium philosophicarum fasciculus
No full textquem ... praeside ... Io. Friderico Benoit ... publicè tutabitur Ioh. Rodolphus Kochius, HBernas, phil. stud. author & respondens, ad diem 5. Martii ...Diss. Hohe Schule Bern, 171
Fables de La Fontaine: Une Anthologie proposée par Benoit Marchon
No full textHere are forty-three fables presented by an artist I have enjoyed twice elsewhere. The book's unusual shape (6½ x 10¾) is the first clue that it is going to present traditional material in a fresh way. Almost every presentation involves two pages and clever positioning of a few key images. GA (10-11) presents an ant with a sack of grain on his back marching across the page above a grasshopper moving upwards with a guitar on his back: character, load, and direction are all different. FC presents a cheese with its owner's name struck through and changed from Corbeau to Renard (12-13). WS shows a stork with a scissors for a head beside an x-ray of a wolf's digestive tract with the bone lodged down the throat (22-23). The spilt milk of MM is blotting out drawings of hens, pig, and cow (30-31). The surreal style fits the approach perfectly. Sometimes I have no idea why an object is presented the way Jarrie presents it; other times it is perfect. The bull in OF holds the frog by a tether as though the latter were a helium-filled balloon (32-33). Maybe best of all is The Rat and the Elephant (50-51). The elephant is segmented to make room for the text. Between the elephant's legs, mostly hidden from us, a cat reaches out a paw for the minuscule rat under the elephant's big belly. For sheer fun, try The Lion Defeated by a Man (78-79). The book has a place-holding ribbon, a short life of both La Fontaine and of Jarrie, and a helpful glossary of unusual language in the fables. This book fulfills its rear cover's promise of a fresh entry into a fabulous zoological park. Bravo, Jarrie!This is a hardbound book (hard cover)Language note: FrenchJean de La Fontaine; Benoit Marcho
L’écriture impliquée: nouvelle forme de l’engagement littéraire chez fatou diome, Léonora Miano et Marie Ndiaye
No full textMade available in DSpace on 2018-09-04T20:36:43Z (GMT). No. of bitstreams: 2
BENOIT-DISSERTATION-2018.pdf: 826258 bytes, checksum: 62bd64e1f91412319b132e14ea06de60 (MD5)
LICENSE.txt: 4212 bytes, checksum: 47cf8a908eb36adb8db64e0e0da466e9 (MD5)
Previous issue date: 2018-04-18Embargo set by: Seth Robbins for item 107270
Lift date: 2020-09-04T20:37:00Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 107270
Lift date: 2020-09-04T20:42:08Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemCette thèse propose d’expliciter les manières dont l’implication se manifeste dans les textes de Fatou Diome, Léonora Miano et Marie NDiaye. Dans un contexte français de résurgence de l’engagement littéraire, elle exprime des manières d’intervenir par l’écriture sur des problèmes sociaux ou politiques qui traversent la société. L’originalité de notre thèse tient à l’intérêt d’avoir privilégié le contexte d’écriture de ces auteures. En effet, la critique des littératures africaines francophones lie l’émergence de nouvelles formes d’écriture, à partir de années quatre-vingt, à la présence des auteurs de cette littérature dans un espace qui n’est plus africain mais essentiellement parisien. Le choix de l’implication nous permet d’inscrire les écrivaines choisies pour notre analyse dans un lieu témoin de pratiques d’écritures nouvelles qui montrent des préoccupations qui ne sont plus uniquement d’ordre esthétique.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-05-01The student, Malyoune Benoit, accepted the attached license on 2018-04-18 at 07:03.The student, Malyoune Benoit, submitted this Dissertation for approval on 2018-04-18 at 07:11.This Dissertation was approved for publication on 2018-04-18 at 17:39.DSpace SAF Submission Ingestion Package generated from Vireo submission #12334 on 2018-08-31 at 17:20:24U of I Only Restriction Lifted for Item 107270 on 2020-09-05T09:15:26Z
- …
