Développement et caractérisation de dérivés dipyrrométhène pour des applications dans le domaine du photovoltaïque

Ce projet de recherche mené en collaboration industrielle avec St-Jean Photochimie Inc. / PCAS Canada vise le développement et la caractérisation de dérivés dipyrrométhène pour des applications dans le domaine du photovoltaïque. La quête du récoltage des photons se situant dans le proche-infrarouge a été au centre des modifications structurales explorées afin d’augmenter l’efficacité de conversion des cellules solaires de type organique et à pigments photosensibles. Trois familles de composés intégrant le motif dipyrrométhène ont été synthétisées et caractérisées du point de vue spectroscopique, électrochimique, structural ainsi que par modélisation moléculaire afin d’établir des relations structures-propriétés. La première famille comporte six azadipyrrométhènes au potentiel de coordination tétradentate sur des centres métalliques. Le développement d’une nouvelle voie synthétique asymétrique combinée à l’utilisation d’une voie symétrique classique ont permis d’obtenir l’ensemble des combinaisons de substituants possibles sur les aryles proximaux incluant les noyaux 2-hydroxyphényle, 2-méthoxyphényle et 2- pyridyle. La modulation du maximum d’absorption dans le rouge a pu être faite entre 598 et 619 nm. De même, la présence de groupements méthoxyle ou hydroxyle augmente l’absorption dans le violet (~410 nm) tel que démontré par modélisation. La caractérisation électrochimique a montré que les dérivés tétradentates étaient en général moins stables aux processus redox que leur contre-parti bidentate. La deuxième famille comporte dix dérivés BODIPY fusionnés de façon asymétrique en position [b]. L’aryle proximal a été modifié de façon systématique afin de mieux comprendre l’impact des substituents riches en électron et de la fusion de cycles aromatiques. De plus, ces dérivés ont été mis en relation avec une vaste série de composés analogues. Les résultats empiriques ont montré que les propriétés optoélectroniques de la plateforme sont régies par le degré de communication électronique entre l’aryle proximal, le pyrrole sur lequel il est attaché et le noyau indolique adjacent à ce dernier. Les maximums d’absorption dans le rouge sont modulables entre 547 et 628 nm et la fluorescence des composés se situe dans le proche- infrarouge. L’un des composé s’est révélé souhaitable pour une utilisation en photovoltaïque ainsi qu’à titre de sonde à pH. La troisième famille comporte cinq complexes neutres de RuII basés sur des polypyridines et portant un ligand azadipyrrométhène cyclométalé. Les composés ont montré une forte absorption de photons dans la région de 600 à 800 nm (rouge à proche- infrarouge) et qui a pu être étendue au-delà de 1100 nm dans le cas des dérivés portant un ligand terpyridine. L’analyse des propriétés optoélectroniques de façon empirique et théorique a montré un impact significatif de la cyclométalation et ouvert la voie pour leur étude en tant que photosensibilisateurs en OPV et en DSSC. La capacité d’un des complexes à photo-injecter un électron dans la bande de conduction du semi-conducteur TiO2 a été démontré en collaboration avec le groupe du Pr Gerald J. Meyer à University of North Carolina at Chapel Hill, premier pas vers une utilisation dans les cellules solaires à pigments photosensibles. La stabilité des complexes en solution s’est toutefois avérée problématique et des pistes de solutions sont suggérées basées sur les connaissances acquises dans le cadre de cette thèse.

Développement et caractérisation de dérivés dipyrrométhène pour des applications dans le domaine du photovoltaïque

Ce projet de recherche mené en collaboration industrielle avec St-Jean Photochimie Inc. / PCAS Canada vise le développement et la caractérisation de dérivés dipyrrométhène pour des applications dans le domaine du photovoltaïque. La quête du récoltage des photons se situant dans le proche-infrarouge a été au centre des modifications structurales explorées afin d’augmenter l’efficacité de conversion des cellules solaires de type organique et à pigments photosensibles. Trois familles de composés intégrant le motif dipyrrométhène ont été synthétisées et caractérisées du point de vue spectroscopique, électrochimique, structural ainsi que par modélisation moléculaire afin d’établir des relations structures-propriétés. La première famille comporte six azadipyrrométhènes au potentiel de coordination tétradentate sur des centres métalliques. Le développement d’une nouvelle voie synthétique asymétrique combinée à l’utilisation d’une voie symétrique classique ont permis d’obtenir l’ensemble des combinaisons de substituants possibles sur les aryles proximaux incluant les noyaux 2-hydroxyphényle, 2-méthoxyphényle et 2- pyridyle. La modulation du maximum d’absorption dans le rouge a pu être faite entre 598 et 619 nm. De même, la présence de groupements méthoxyle ou hydroxyle augmente l’absorption dans le violet (~410 nm) tel que démontré par modélisation. La caractérisation électrochimique a montré que les dérivés tétradentates étaient en général moins stables aux processus redox que leur contre-parti bidentate. La deuxième famille comporte dix dérivés BODIPY fusionnés de façon asymétrique en position [b]. L’aryle proximal a été modifié de façon systématique afin de mieux comprendre l’impact des substituents riches en électron et de la fusion de cycles aromatiques. De plus, ces dérivés ont été mis en relation avec une vaste série de composés analogues. Les résultats empiriques ont montré que les propriétés optoélectroniques de la plateforme sont régies par le degré de communication électronique entre l’aryle proximal, le pyrrole sur lequel il est attaché et le noyau indolique adjacent à ce dernier. Les maximums d’absorption dans le rouge sont modulables entre 547 et 628 nm et la fluorescence des composés se situe dans le proche- infrarouge. L’un des composé s’est révélé souhaitable pour une utilisation en photovoltaïque ainsi qu’à titre de sonde à pH. La troisième famille comporte cinq complexes neutres de RuII basés sur des polypyridines et portant un ligand azadipyrrométhène cyclométalé. Les composés ont montré une forte absorption de photons dans la région de 600 à 800 nm (rouge à proche- infrarouge) et qui a pu être étendue au-delà de 1100 nm dans le cas des dérivés portant un ligand terpyridine. L’analyse des propriétés optoélectroniques de façon empirique et théorique a montré un impact significatif de la cyclométalation et ouvert la voie pour leur étude en tant que photosensibilisateurs en OPV et en DSSC. La capacité d’un des complexes à photo-injecter un électron dans la bande de conduction du semi-conducteur TiO2 a été démontré en collaboration avec le groupe du Pr Gerald J. Meyer à University of North Carolina at Chapel Hill, premier pas vers une utilisation dans les cellules solaires à pigments photosensibles. La stabilité des complexes en solution s’est toutefois avérée problématique et des pistes de solutions sont suggérées basées sur les connaissances acquises dans le cadre de cette thèse.

Understanding the very nature of Project Management : a praxiological approach

Foreword: In this paper I call upon a praxiological approach. Praxeology (early alteration of praxiology) is the study of human action and conduct. The name praxeology/praxiologyakes is root in praxis, Medieval Latin, from Greek, doing, action, from prassein to do, practice (Merriam-Webster Dictionary). Having been involved in project management education, research and practice for the last twenty years, I have constantly tried to improve and to provide a better understanding/knowledge of the field and related practice, and as a consequence widen and deepen the competencies of the people I was working with (and my own competencies as well!), assuming that better project management lead to more efficient and effective use of resources, development of people and at the end to a better world. For some time I have perceived a need to clarify the foundations of the discipline of project management, or at least elucidate what these foundations could be. An immodest task, one might say! But not a neutral one! I am constantly surprised by the way the world (i.e., organizations, universities, students and professional bodies) sees project management: as a set of methods, techniques, tools, interacting with others fields – general management, engineering, construction, information systems, etc. – bringing some effective ways of dealing with various sets of problems – from launching a new satellite to product development through to organizational change.

A combined neutralization-reionization mass spectrometric and theoretical study of oxyallyl and other elusive [C3,H4,O] neutrals

Five different anionic [C3′H4′O]•- isomers, i.e. the radical anions of acrolein, acetyl carbene, formyl methyl carbene, methoxy vinylidene, and oxyallyl are generated in an ion beam mass spectrometer and subjected to neutralization-reionization (NR) mass spectrometric experiments including neutral and ion decomposition difference (NIDD) mass spectrometry; the latter allows for the examination of the neutrals' unimolecular reactivity. Further, the anionic, the singlet and triplet neutral, and the cationic [C3′H4′O] •-/0/•+ potentialenergy surfaces are calculated at the B3LYP/6-311++G(d,p) level of theory. For some species, notably the singlet state of oxyallyl, the theoretical treatment is complemented by G2, CASSCF, and MR-CI calculations. Theory and experiment are in good agreement in that at the neutral stage (i) acrolein does not react within the μsec timescale, (ii) acetyl and formyl methyl carbenes isomerize to methyl ketene, (iii) methoxy vinylidene rearranges to methoxy acetylene, (iv) singlet 1A1 oxyallyl undergoes ring closure to cyclopropanone, and (v) triplet 3B2 oxyallyl may have a lifetime sufficient to survive a NR experiment.

Analysis Of Curved Laminated Beams Of Bimodulus Composite-Materials

Composite materials exhibiting different moduli in tension and in compression, commonly called as bimodular composites are being used in many engineering fields. A finite element analysis is carried out for small deflection static behavior of laminated curved beams of bi modulus materials for both solid and hollow circular cross-sections using an iterative procedure. The finite element has 16 d.o.f. and uses the displacement field in terms of first order Hermite in terpolation polynomials. The neutral surface, i.e. the locus of points having zero axial strain is found to vary drastically depending on the loading, lay up schemes and radius of curvature. As il lustrations, plots of the cross-sections of the ruled neutral-surface are presented for some of the investigated cases. Using this element a few problems of curved laminated beams of bimodulus materials are solved for both solid and hollow circular cross-sections.

Spectroscopic and Coordination Behavior of α-Cyanothioacetamide

α-Cyanothioacetamide (CTAM) complexes of cuprous chloride CuCl–2CTAM and cuprous bromide CuBr–2CTAM have been prepared. The infrared spectra of CTAM and its complexes, and the laser Raman spectrum of CTAM have been recorded. Assignment of the frequencies of the ligand has been made on the basis of a normal coordinate analysis using the Urey-Bradley force field. The copper (I) complexes are inferred to have thiocarbonyl sulfur and amide nitrogen bonded CTAM as evidenced from infrared and electronic spectra.

Conformational analysis of D-pantothenic acid

The conformational analysis of d-pantothenic acid using classical semiempirical methods has been carried out. The pantothenic acid molecule can exist in the neutral form (I) or in the ionised form (II) with a deprotonated negatively charged carboxyl group. The neutral molecule as well as the anion is highly flexible and has an ensemble of several allowed conformations rather than one or two unique conformations. The distribution of allowed conformations indicate that the β-alanine as well as the pantoic acid part of the molecule prefers partially folded conformations. The conformation of the former is greatly affected by the ionisation state of the carboxyl group whereas that of the latter is not. Possibility of intramolecular hydrogen bonding in different allowed conformations has also been explored. A bifurcated hydrogen bond involving a carboxyl (or carboxylate) oxygen atom and a hydroxyl oxygen atom, as acceptors, and the amide nitrogen atom as the donor occurs frequently in both I and II. Amongst the two crystal structures containing pantothenic acid reported so far, the conformation of the molecule in l-lysine d-pantothenate lies in the allowed region and is stabilised by a bifurcated intramolecular hydrogen bond, whereas that in the calcium bromide salt falls in a disallowed region, presumably due to the requirement of tridentate metal coordination.

From the {Cu(μ2-S)N}4 butterfly architecture to the {Cu(μ3-S)N}12 double wheel

Copper(I) complexes with {Cu(μ2-S)N}4 and {Cu(μ3-S)N}12 core portions of butterfly-shaped or double wheel architectures have been isolated in the reaction of Cu(I) with the Schiff base ligand C6H4(CHNC6H4S)2, aiso-abtâ, under different conditions. View the MathML source containing the tetranuclear electroneutral complex View the MathML source is formed by the reaction of CuI in acetonitrilic solution and recrystallization from DMF, whereas View the MathML source containing dodecanuclear View the MathML source wheels is accessible starting from CuBF4. Complexes 2 and 4 represent the first examples of cyclic complexes with the same overall stoichiometry but different ring sizes. The ligand induces two different coordination environments around copper(I) by switching between μ2- and μ3-sulfur bridging modes.

Studies on some metal monothiobenzoates

Monothiobenzoate (MTB) (Chemical Equation Presented) complexes with the molecular formulas Cr(MTB)3, [Ni(MTB)2]n, [Zn(MTB)2]n, [Cd(MTB)2]n, [Hg(MTB)2]n, [Cu(MTB)]n, and [Ag(MTB)]n have been prepared and studied. All the complexes are nonionic in acetonitrile. Only the chromium complex is soluble in nitrobenzene and found to be monomeric cryoscopically. The thiobenzoate ligand appears to be asymmetrically chelated in Cr(III) and Cd(II) complexes, with stronger oxygen and sulfur coordination, respectively, while practically symmetrically coordinated in Ni(II) and Zn(II) complexes. These four complexes are assigned distorted octahedral structures around the metal ion. The coordination in Hg(II), Cu(I), and Ag(I) complexes is mainly through sulfur indicating the monodentate nature of the thiobenzoate ligand in these complexes. The coordination of monothiobenzoate ion in the complexes has been rationalized in terms of "hard" and "soft" acid-base concept.

Zirconocenes as models for homogeneous Ziegler-Natta olefin polymerization catalysts

Using density functional theory, we studied the fundamental steps of olefin polymerization for zwitterionic and cationic Group IV ansa-zirconocenes and a neutral ansa- yttrocene. Complexes [H₂E(C₅H₄)₂ZrMe]ⁿ (n = 0: E = BH₂ (1), BF₂ (2), AlH₂(3); n = +: E = CH₂(4), SiH₂(5)) and H₂Si(C₅H₄)₂YMe were used as computational models. The largest differences among these three classes of compounds were the strength of olefin binding and the stability of the β-agostic alkyl intermediate towards β-hydrogen elimination. We investigated the effect of solvent on the reaction energetics for land 5. We found that in benzene the energetics became very similar except that a higher olefin insertion barrier was calculated for 1. The calculated anion affinity of [CH₃BF₃]^- was weaker towards 1 than 5. The calculated olefin binding depended primarily on the charge of the ansa linker, and the olefin insertion barrier was found to decrease steadily in the following order: [H₂C(C₅H₄)₂ZrMe]⁺ > [F₂B(C₅H₄)₂ZrMe] ≈ [H₂B(C₅H₄)₂ZrMe] > [H₂Si(C₅H₄)₂ZrMe]⁺ > [H₂Al(C₅H₄)₂ZrMe].

We prepared ansa-zirconocene dicarbonyl complexes Me₂ECp₂Zr(CO)₂ (E = Si, C), and t-butyl substituted complexes (t-BuCp)₂Zr(CO)₂, Me₂E(t-BuCp)₂Zr(CO)₂ (E = Si, C), (Me₂Si)₂(t-BuCp)₂Zr(CO)₂ as well as analogous zirconocene complexes. Both the reduction potentials and carbonyl stretching frequencies follow the same order: Me₂SiCp₂ZrCl₂> Me₂CCp₂ZrCl₂> Cp₂ZrCl₂> (Me₂Si)₂Cp₂ZrCl₂. This ordering is a result of both the donating abilities of the cyclopentadienyl substituents and the orientation of the cyclopentadiene rings. Additionally, we prepared a series of analogous cationic zirconocene complexes [LZrOCMe₃][MeB(C₆F₅)₃] (L = CP₂, Me₂SiCp₂, Me₂CCP₂, (Me₂Si)₂Cp₂) and studied the kinetics of anion dissociation. We found that the enthalpy of anion dissociation increased from 10.3 kcal•mol^-1 to 17.6 kcal•mol^-1 as exposure of the zirconium center increased.

We also prepared series of zirconocene complexes bearing 2,2-dimethyl-2-sila-4-pentenyl substituents (and methyl-substituted olefin variants). Methide abstraction with B(C₆F₅) results in reversible coordination of the tethered olefin to the cationic zirconium center. The kinetics of olefin dissociation have been examined using NMR methods, and the effects of ligand variation for unlinked, singly [SiMe₂]-linked and doubly [SiMe₂]-linked bis(cyclopentadienyl) arrangements has been compared (ΔG‡ for olefin dissociation varies from 12.8 to 15.6 kcal•mol^-1). Methide abstraction from 1,2-(SiMe₂)₂(η⁵-C₅H₃)₂Zr(CH₃)-(CH₂CMe₂CH₂CH = CH₂) results in rapid β-allyl elimination with loss of isobutene yielding the allyl cation [{1,2-(SiMe₂)₂(η⁵-C₅H₃)₂Zr(η³-CH₂CH=CH₂)]⁺.

Electrospinning of multicomponent ultrathin fibrous nonwovens for semi-occlusive wound dressings

This work describes the design and assembly of multifunctional and cost-efficient composite fiber nonwovens as semi-occlusive wound dressings using a simple electrospinning process to incorporate a variety Of functional components into an Ultrathin fiber. These components include non-hydrophilic poly(L-lactide) (PLLA) as fibrous backbone, hydrophilic poly(vinyl pyrrolidone)iodine (PVP-I), TiO2 nanoparticles, zinc chloride as antimicrobial, odor-controlling, and antiphlogistic agents, respectively. The process of synthesis starts with a multicomponent solution Of PLLA, PVP, TiO2 nanoparticles plus zinc chloride, in which TiO2 nanoparticles are synthesized by in situ hydrolysis of TiO2 precursors in a PVP Solution for the sake of obtaining the particle-uniformly dispersive solution. Subsequent electrospinning generates the corresponding composite fibers. A further iodine vapor treatment to the composite fibers combines iodine with PVP to produce the PVP-I complexes. Experiments indicate that the assembled composite fibers (300-400 nm) possess the ointment-releasing characteristic and the phase-separate, core-sheath structures in which PVP-I residing in fiber Surface layer becomes the sheath, and PLLA distributing inside the fiber acts as the core.

Preparation and characterization of novel luminescent sol-gel films containing a RE3+ carboxylic acid complex

RE3+ (Eu3+, Tb3+) complexes with carboxylic acid (salicylic acid and benzoic acid) were introduced into the sol, which was prepared by the hydrolysis of tetraethoxysilane (TEOS). A sol-gel luminescent thin film (SG-LTF) was then prepared by dispersing the sol onto a silica substrate by a spin coating method. Multi-layer luminescent thin films were prepared by repeating the same process. The luminescent spectra, fluorescence lifetime and thermal stability of the SG-LTFs were investigated. For the reason of comparison polyvinylbutyral (PVB) was added into a N,N-dimethylformamide (DMF) solution in which the comparative RE3+ carboxylic acid complexes were previously dissolved to form the DMF/PVB solution and the PVB luminescent thin film (PVB-LTF) was prepared. The results show that a broad excitation band indicates the formation of RE complexes in the solid SG-LTFs. RE ions, which are restrained in the silica matrix, present longer lifetimes and higher thermal stability than that in the PVB-LTF containing the corresponding pure complexes. The different doping concentration of RE (III) complexes in the SG-LTFs and the different change of the emission intensities with the heat treatment temperature in the sol-gel thin film and the sol-gel bulk gel were also discussed in this paper.

A NEW METHOD FOR THE SYNTHESIS OF LN(ETA-6-C6ME6)(ALCL4)3 (LN=ND, SM, GD, YB), AND THE X-RAY CRYSTAL-STRUCTURE OF YB(ETA-6-C6ME6)(ALCL4)3.MEC6H5

A series of neutral eta6-C6Me6 complexes of lanthanide elements Ln(176-C6Me6)(AlCl4)3 . MeC6H5(Ln = Nd, Sm, Gd, Yb) has been prepared directly in good yields from the reaction of LnCl3, AlCl3 and C6Me6 in toluene. The complexes have been characte

Isolation of PSI from a siphonous marine green alga, Codium fragile

Three different forms of PS I complexes were isolated from a siphonous marine green alga, Codium fragile, by Triton X-100 sucrose gradient centrifugation. Zone III had a Chl a/b>20, and designated as PS I. core complex CC I because it created only CP I band in mild PAGE. Zone IV and V had absorption at 436 and 674 nm, 467 and 650 nm, and 540 nm, suggesting the presence of Chl a, Chl b, siphonaxanthin and siphonein, Chl a/b were 3.23 and 2.4, respectively. Both CP I and CP I a bands were observed when they were subjected to mild PAGE. Therefore, Zone IV and V were different forms of PS I complexes that consisted of CC I and different amount of light-harvesting complex LHC I. Zone III contained only 66 and 56 ku peptides in SDS-PAGE, while Zone IV and V had 4 different LHC I peptides of 25, 26, 26.2 and 27.5 ku in addition to 66, 56 ku peptides. Fluorescence emission spectra showed that efficient energy transfer were kept among pigments in isolated PS I complexes. Excitation energy absorbed by Chl b, siphonaxanthin and siphonein can be transferred to Chl a.

First EXAFS studies on aurophilic interactions in solution

EXAFS has been used to directly show the existence of Au…Au interactions in dissolved Au(I) complexes for the first time; the information has been used to understand the optical properties of these materials.