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William G. Skene - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Triphenylamine–Thiophene–Azomethine Derivatives: Toward Understanding Their Electrochromic Behavior
The Journal of Physical Chemistry C, 2016Co-Authors: Marie-hélène Tremblay, Thomas Skalski, Yohan Gautier, Grégory Pianezzola, William G. SkeneAbstract:A series of thiophenoAzomethines connected to a central triphenylamine were prepared. The effect of the type of aminothiophene used to prepare the conjugated Azomethines and the number of Azomethine bonds, ranging from one to three, flanking the triphenylamine on the spectral, electrochemical, and spectroelectrochemical properties were investigated. Both the absorption and fluorescence of the Azomethines (6–8) derived from 2,5-diaminothiophene (1) were found to be contingent on the number of the Azomethines. The spectral properties were red-shifted with increasing the number of Azomethine bonds. In contrast, the Azomethines (9–11) derived from 2-aminothiophene (2) were not perturbed by the number of Azomethines. However, their spectral properties were red-shifted relative to their triphenylamine counterparts derived from 1. The oxidation potentials of the Azomethines were also contingent on structure. They were shifted to more positive potentials with increasing number of Azomethines. The oxidation potent...
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Towards multichromatic electrochromes from ambipolar conjugated Azomethines
New Journal of Chemistry, 2014Co-Authors: Michael E. Mulholland, Daminda Navarathne, Samim Khedri, William G. SkeneAbstract:A series of conjugated Azomethines end-capped with phenylamides and consisting of different aromatic cores of varying π-donor strength were prepared. Their optical and electrochemical properties were investigated to assess the suitability of the Azomethines as electrochromic materials. The Azomethines were found to undergo both electrochemical oxidation and reduction in the window of −1.60 and +1.35 V vs. Ag/Ag+. The color of the ambipolar compounds could be dramatically changed when switched between their reduced, neutral, and oxidized states. The color of the different states was contingent on the π-donor strength of the central aromatic unit. The largest spectral difference of 350 nm between the reduced and oxidized states was observed when the central aromatic group was 3,4-ethylenedioxythiophene (EDOT). The colors detectable by the eye for this EDOT derivative were blue, red, and bleached for the reduced, neutral, and oxidized states, respectively. The multichromatic Azomethine was used as an electrochromic layer in a functioning device. The proof-of-concept ambipolar electrochromic device could be repeatedly switched between its orange (neutral) and purple (reduced) states. The device could also be switched to its oxidized (bleached) state.
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Charge-Carrier Transport in Thin Films of π-Conjugated Thiopheno-Azomethines
Organic Electronics, 2012Co-Authors: Dilek Isik, Clara Santato, Satyananda Barik, William G. SkeneAbstract:In this work, we explored the capacity of p-conjugated thiopheno-Azomethines in the form of thin films for use in organic electronic applications. The charge-carrier transport properties of the p-conjugated thiopheno-Azomethines were obtained in field-effect transistor configuration after the characterization of the film forming properties by fluorescence hyperspectral imaging and atomic force microscopy. We observed a semiconducting behavior for the Azomethines investigated, being an oligomer thiophene triad, consisting of two Azomethine bonds, and its polymer counterpart, consisting of about 15 Azomethines bonds. The charge transport properties of an analogous thiophene vinylene triad were also examined for validating the mobility measurements, because such compounds are known to have hole transport properties. The Azomethine triad was found to have a hole mobility of 3 � 10 � 5 cm 2 /Vs.
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EDOT-containing Azomethine: an easily prepared electrochromically active material with tuneable colours
Journal of Materials Chemistry, 2010Co-Authors: Andreanne Bolduc, Stéphane Dufresne, William G. SkeneAbstract:An Azomethine derived from EDOT segments was easily prepared and exhibited reversible oxidation. The spectroelectrochemical behaviour of this EDOT containing Azomethine was observed as intense colour changes for the oxidized products relative to the neutral form. Multiple reversible colours states were observed with the anodically and hydrolytically stable Azomethine upon electrochemical and chemical oxidation.
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Conjugated fluorenes prepared from Azomethines connections--II: The effect of alternating fluorenones and fluorenes on the spectroscopic and electrochemical properties.
The journal of physical chemistry. B, 2009Co-Authors: Stéphane Dufresne, Laura Callaghan, William G. SkeneAbstract:The photophysics and electrochemistry of fluorene and fluorenone Azomethine derivatives were examined in order to understand the deactivation pathways responsible for the quenched fluorescence of these compounds, which should otherwise be fluorescent. Steady-state fluorescence showed that the fluorene singlet excited state is quenched both by fluorenone (1) and a model aliphatic Azomethine compound (14) with kq ≈ 1010 M−1 s−1. The quencher concentration required to deactivate 95% of the excited singlets formed was 8.4 mM for fluorenone and 34 mM for 14. Intramolecular photoinduced electron transfer (PET) from fluorene to both 1 and 14 was found as the principle deactivation mode of the fluorene’s excited state. The high degree of conjugation of the Azomethines promotes intersystem crossing to the triplet manifold by narrowing the singlet−triplet energy gap, which is also in part responsible for the reduced fluorescence observed for the fluorenone Azomethine derivatives 5−11. Fluorescence quenching by PET ...
W. G. Skene - One of the best experts on this subject based on the ideXlab platform.
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Surface immobilized Azomethine for multiple component exchange.
Soft matter, 2017Co-Authors: Michael Lerond, Daniel Bélanger, W. G. SkeneAbstract:Diazonium chemistry concomitant with in situ electrochemical reduction was used to graft an aryl aldehyde to indium-tin oxide (ITO) coated glass substrates. This served as an anchor for preparing electroactive Azomethines that were covalently bonded to the transparent electrode. The immobilized Azomethines could undergo multiple step-wise component exchanges with different arylamines. The write–erase–write sequences were electrochemically confirmed. The Azomethines could also be reversibly hydrolyzed. This was exploited for multiple Azomethine-hydrolysis cycles resulting in discrete electroactive immobilized Azomethines. The erase–rewrite sequences were also electrochemically confirmed.
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Turning‐on the Quenched Fluorescence of Azomethines through Structural Modifications
European Journal of Organic Chemistry, 2013Co-Authors: Satyananda Barik, W. G. SkeneAbstract:A series of fluorene Azomethines were prepared to examine the effect of structural modification on the absolute fluorescence quantum yields (Φfl). The change in fluorescence occurring upon reversing the orientation of the Azomethine bond, the number of fluorene units, and alkylation at the 9,9′-positions of fluorene was examined. It was found that Φfl could be tailored with these structural modifications with 0.05 ≤ Φfl ≤ 0.45. The highest Φfl was measured for the trimer derived from 2,7-diamino fluorene with each fluorene being alkylated at the 9,9′-positions. The fluorescence quantum yields did not increase at 77 K, implying the absence of fluorescence quenching modes involving internal conversion. Fluorescence enhancement was also not observed upon protonating the imine with trifluoroacetic acid. This confirms that Waldon inversion and isomerization are not fluorescence deactivation modes. Additionally, no photoisomerization was observed either at room temperature or at 77 K when the fluorene derivatives were irradiated at 354 nm. In contrast, the Z photoisomer of a N-benzylideneaniline analogue was spectroscopically detected both by absorbance and by 1H NMR spectroscopy.
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chemical doping of edot Azomethine derivatives insight into the oxidative and hydrolytic stability
Journal of Materials Chemistry, 2012Co-Authors: Andreanne Bolduc, Stéphane Dufresne, W. G. SkeneAbstract:A series of EDOT (3,4-ethylenedioxythiophene) containing Azomethines were prepared for investigating their opto-electronic properties. These properties were compared to those of their thiophene Azomethine counterparts and it was found that incorporating the EDOT moiety resulted in a 30 nm bathochromic shift in the absorbance. Meanwhile, the oxidation potential (Epa) could be reduced by 100 mV by incorporating the electron rich moiety. Cyclic voltammetry revealed a one-electron oxidation process, resulting in a radical cation. This intermediate was stable when the Azomethines contained amines in the 2,2′-positions, evidenced by the reversible oxidation in cyclic voltammetry. In contrast, the radical cation was irreversible when the 2,2′-positions were unsubstituted. It was found that the resulting radical cation was coupled by standard anodic polymerisation to form a polymer that was physisorbed onto the ITO electrode. The resulting polymer was mauve in colour with a λmax of 515 nm and a degree of polymerisation of ca. 5. This was spectroscopically determined relative to an EDOT polyAzomethine derivative and a soluble thiophene polyAzomethine. The stability of the EDOT Azomethine derivatives towards electrochemical and chemical oxidation was also spectroscopically investigated. It was found that the resulting radical cation exhibited a ca. 100 nm bathochromic shift in absorbance relative to the neutral form and reversible colour switching between the neutral and oxidized states was possible. Chemical doping with FeCl3 generated a stable dication. High contrast colours between the neutral and oxidized states of the Azomethines were observed. Multiple oxidation/neutralisation cycles were possible without detectable colour deterioration, demonstrating the chemical robustness of the conjugated Azomethines towards oxidative decomposition and hydrolysis.
Paul W. Groundwater - One of the best experts on this subject based on the ideXlab platform.
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1,7-Electrocyclizations of Azomethine Ylides : Scope and Synthetic Aspects
Synlett, 2008Co-Authors: Miklos Nyerges, Judit Toth, Paul W. GroundwaterAbstract:The 1,3-dipolar cycloaddition of Azomethine ylides is a versatile and efficient tool for the construction of five-membered nitrogen heterocycles. When the Azomethine ylide is conjugated with double bonds other pericyclic pathways become available, including 1,5- or 1,7-electrocyclizations, with the latter 8π-electron process having only recently emerged as a potentially useful method for the formation of seven-membered heterocycles. Under special structural circumstances, multistep rearrangements can also be observed. In this account, a summary of our work on the exploration and development of 1,7-electrocyclizations of Azomethine ylides is presented. 1 Introduction 2 Electrocyclizations 2.1 Reaction of β-Phenylcinnamaldehyde with Amino Acids: The First 1,7-Electrocyclization of Nonstabilized Azomethine Ylides 2.2 Synthesis of Azepines from Unsaturated Aldehydes and Sarcosine via 1,7-Electrocyclizations 2.3 Electrocyclizations of Stabilized Azomethine Ylides 2.4 Electrocyclizations of Azomethine Ylides onto a N=O Double Bond 3 Conclusions
Marie-hélène Tremblay - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Triphenylamine–Thiophene–Azomethine Derivatives: Toward Understanding Their Electrochromic Behavior
The Journal of Physical Chemistry C, 2016Co-Authors: Marie-hélène Tremblay, Thomas Skalski, Yohan Gautier, Grégory Pianezzola, William G. SkeneAbstract:A series of thiophenoAzomethines connected to a central triphenylamine were prepared. The effect of the type of aminothiophene used to prepare the conjugated Azomethines and the number of Azomethine bonds, ranging from one to three, flanking the triphenylamine on the spectral, electrochemical, and spectroelectrochemical properties were investigated. Both the absorption and fluorescence of the Azomethines (6–8) derived from 2,5-diaminothiophene (1) were found to be contingent on the number of the Azomethines. The spectral properties were red-shifted with increasing the number of Azomethine bonds. In contrast, the Azomethines (9–11) derived from 2-aminothiophene (2) were not perturbed by the number of Azomethines. However, their spectral properties were red-shifted relative to their triphenylamine counterparts derived from 1. The oxidation potentials of the Azomethines were also contingent on structure. They were shifted to more positive potentials with increasing number of Azomethines. The oxidation potent...
José A. S. Cavaleiro - One of the best experts on this subject based on the ideXlab platform.
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1,3-dipolar cycloaddition reactions of porphyrins with Azomethine ylides.
The Journal of organic chemistry, 2005Co-Authors: Ana M. G. Silva, Augusto C. Tomé, Maria G. P. M. S. Neves, And Artur M. S. Silva, José A. S. CavaleiroAbstract:The behavior of porphyrins as dipolarophiles in 1,3-dipolar cycloadditions with Azomethine ylides was studied. Depending on the nature of the substituent groups on the porphyrin macrocycles, the reaction can give monoadducts (chlorins) or bisadducts (isobacteriochlorins and bacteriochlorins). When a large excess of Azomethine ylide is used, trisadducts can also be obtained. Mixed isobacteriochlorin derivatives were prepared from the reaction of Azomethine ylides with the chlorin monoadducts previously obtained via Diels−Alder reactions.
