Andréanne Bolduc

Push−Pull Aminobithiophenes — Highly Fluorescent Stable Fluorophores

Stable 2-aminobithiophenes were prepared using the Gewald reaction. The resulting push-pull bithiophenes exhibited both unprecedented high fluorescence yields and stability in addition to demonstrating fluorescence on-off properties.

EDOT-containing azomethine: an easily prepared electrochromically active material with tuneable colours

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.

Survey of recent advances of in the field of π-conjugated heterocyclic azomethines as materials with tuneable properties

This account gives an overview of our recent work in the area of conjugated azomethines derived from 2-aminothiophenes. It will be presented that mild reaction conditions can be used to selectively prepare symmetric and unsymmetric conjugated azomethines. It further will be demonstrated that azomethines consisting of various 5-membered aryl heterocycles lead to chemically, reductively, hydrolytically, and oxidatively robust compounds. The optical and electrochemical properties of these materials can be tuned contingent on the degree of conjugation, type of aryl heterocycle, and by including various electronic groups. The end result is materials having colors spanning 250 nm across the visible spectrum. These colors further can be tuned via electrochemical or chemical doping. The resulting doped states have high color contrasts from their corresponding neutral states. The collective opto-electronic properties and the means to readily tune them, make thiophenoazomethine derivatives interesting materials for potential use in a gamut of applications.

Towards materials with reversible oxidation and tuneable colours using heterocyclic conjugated azomethines

The spectroelectrochemical behaviour of heterocyclic azomethines prepared by condensing complementary aldehydes and amines was observed as intense colour changes of the oxidized products relative to the neutral form. The tuneable colours and reversible oxidation were contingent on the heterocycles.

Conjugated fluorene-thiophenes prepared from azomethine connections. Part I. The effect of electronic and aryl groups on the spectroscopic and electrochemical properties.

The spectroscopic investigation of new fluoreno-thiophene azomethines revealed that these compounds are fluorescent. However, they exhibit reduced fluorescence compared to native fluorene owing to competitive deactivation of the singlet excited state by nonradiative means involving both internal conversion and intersystem crossing. The absorption and emission wavelengths can be tuned and the HOMO-LUMO energy gap modulated from 2.0 to 3.2 eV by incorporating various electronic groups, number of azomethine bonds, and the fluorene-thiophene sequence. Electrochemical investigation confirmed that both oxidation and reduction occur resulting in irreversible radical ion formation.

Chemical doping of EDOT azomethine derivatives: insight into the oxidative and hydrolytic stability

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.

Direct preparation of electroactive polymers on electrodes and their use in electrochromic devices

Thermal polymerization of electroactive thin films using an aminobisthiophene vinylene monomer was done directly on electrodes. The resulting films reversibly switched colors in the visible-to-NIR regions, contingent on the monomers used for polymerization. Working transmissive electrochromic devices were fabricated using the electrode immobilized electroactive polymers. The devices exhibited reversible color changes with a moderate 150 duty cycle.

Polythiophenoazomethines – alternate photoactive materials for organic photovoltaics

Solution-processable polyazomethines containing thiophenes were synthesized and used as the donor material in bulk heterojunction solar cells. The blue polymers exhibited similar electrochemical properties to the benchmark P3HT with the advantage of absorbing more of the visible spectrum. The resulting photovoltaic devices using polyazomethines in the photoactive layer with PC60BM as the acceptor showed power conversion efficiencies up to 0.22% under simulated 100 mW cm−2 AM 1.5G irradiation. The low efficiencies are ascribed to poor charge generation because of too coarse bulk heterojunction morphology formation.

The six-membered-ring azomethine N-((E)-{5-[(E)-(pyridin-3-ylimino)methyl]thiophen-2-yl}methylidene)pyridin-3-amine

The title compound, C16H12N4S, forms a three-dimensional layered network structure via intermolecular hydrogen bonding and π-stacking. The azomethine molecule adopts the thermodynamically stable E regioisomer and the pyridine substituents are antiperiplanar. The mean planes of the pyridine rings and the azomethine group to which they are connected are twisted by 27.27 (5) and 33.60 (5)°. The electrochemical energy gap of 2.3 eV based on the HOMO-LUMO energy difference is in agreement with the spectroscopically derived value.

Diethyl 2,5-bis-[(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)methyl-idene-amino]-thio-phene-3,4-dicarboxyl-ate acetone monosolvate.

The unique 3,4-ethylenedioxythiophene (EDOT) unit of the title compound, C24H22N2O8S3·C3H6O, is twisted by 1.9 (3)° relative to the central thiophene ring. The three heterocyclic units are antiperiplanar. In the crystal, inversion dimers linked by pairs of C—H⋯O hydrogen bonds connect the heterocycles. π–π interactions occur between the central thiophene and the imine bond of the molecule [distance between the ring centroid of the ring and the azomethine bond = 3.413 (3) Å.