Redox active molecules with molecular electronics and synthetic applications

Redox active molecules are ubiquitous to nature and have properties that make them coveted targets for applications in areas of synthesis as well as for the development of materials. This thesis describes the synthesis and characterisation of several flavin donor-acceptor dyads designed around an oligothiophene donor backbone and a flavin acceptor moiety. These show potential applications as optoelectronic materials. It also describes the synthesis of a ferrocene-flavin tetracyanobutadiene super-acceptor compound which showed preliminary evidence of non-linear-optic effects. Finally, a novel method was developed to investigate the redox umpolung activated reactions of vinylferrocene. The vinyl group of vinylferrocene was activated by polarity inversion of ferrocene to ferrocenium and was able to undergo Diels-Alder cycloadditions with cyclobutadiene and furan, as well as, Markovnikov addition of thiols. These reactions were then used to explore the use of vinylferrocene as a redox auxiliary and as a redox active tag in polymers and have the potential to be used in nanoparticles as well as biological systems

Redox-mediated reactions of vinylferrocene: Toward redox auxiliaries

Chemical redox reactions have been exploited to transform unreactive vinylferrocene into a powerful dienophile for the Diels–Alder reaction and reactive substrate for thiol addition reactions upon conversion to its ferrocenium state. We have further investigated the ability of these reactions to facilitate redox-auxiliary-like reactivity by further hydrogenolyisis of the Diels–Alder adduct to the corresponding cyclopentane derivative

An investigation of the role the donor moiety plays in modulating the efficiency of ‘donor-π-acceptor-π-acceptor’ organic DSSCs

Three ‘D-π-A-π-A’ based dyes have been synthesized featuring MeO-, MeS- and Me2N- as donor residues and benzothiadiazole and cyanoacrylic acid residues as acceptor units. UV–vis spectroscopy, solution electrochemistry and DFT modelling indicated that the Me2N- residue has the most significant effect on optical and redox properties of a photosensitizer. DSSCs with the Me2N- functionalized dye gave the highest power conversion efficiency of the series (η = 5.61%), presumably due to the better donor ability of this unit, which promotes more effective intramolecular charge transfer (ICT) characteristics

Metal-free organic chromophores featuring an ethynyl-thienothiophene linker with an n-hexyl chain for translucent dye-sensitized solar cells

We report the simple synthesis of two organic chromophores featuring an ethynyl-thienothiophene linker with an n-hexyl chain (CSD-03 and CSD-04), their optical and electrochemical properties, and their use as photosensitizers in dye-sensitized solar cells (DSSCs). Our theoretical and experimental studies show that adding the second thienothiophene allows for narrowing the bandgap of the molecule and thus ensuring more light harvesting in the visible region. The efficiencies of both CSD-03 (5.46 ± 0.03%) and CSD-04 (5.20 ± 0.03%) are comparable to that of N719 (5.92 ± 0.01%) in translucent DSSCs fabricated with 5 μm-thick TiO2 photoanodes

Metal-free organic chromophores featuring an ethynyl-thienothiophene linker with an n-hexyl chain for translucent dye-sensitized solar cells

We report the simple synthesis of two organic chromophores featuring an ethynyl-thienothiophene linker with an n-hexyl chain (CSD-03 and CSD-04), their optical and electrochemical properties, and their use as photosensitizers in dye-sensitized solar cells (DSSCs). Our theoretical and experimental studies show that adding the second thienothiophene allows for narrowing the bandgap of the molecule and thus ensuring more light harvesting in the visible region. The efficiencies of both CSD-03 (5.46 ± 0.03%) and CSD-04 (5.20 ± 0.03%) are comparable to that of N719 (5.92 ± 0.01%) in translucent DSSCs fabricated with 5 μm-thick TiO2 photoanodes

Coplanar donor-π-acceptor dyes featuring a furylethynyl spacer for dye-sensitized solar cells

Coplanar metal-free organic dyes featuring a furylethynyl spacer with different donor residues (MeO-, MeS-, and Me2N-) have been synthesized. Density functional theory (DFT) calculations predicted that the Me2N- residue would facilitate more effective charge transfer from donor to acceptor than the MeO- and MeS- residues. In agreement with DFT calculations, the dye-sensitized solar cells (DSSCs) fabricated with the Me2N- functionalized dye exhibited the best power conversion efficiency (η), 2.88%. Furthermore, the effect of the furan spacer on the photophysical properties and DSSC parameters are discussed in comparison to a previously reported thiophene counterpart

Bilateral Pneumothorax and Subcutaneous Emphysema following Endoscopic Retrograde Cholangiopancreatography: A Rare Complication.

Endoscopic Retrograde Cholangiopancreatography (ERCP) is a widely used diagnostic and therapeutic modality in the management of biliary and pancreatic disease. Some of the complications of the procedure, although rare, may carry significant morbidity and mortality risks. We describe the case of a 68-year-old female who underwent elective ERCP for ductal stone clearance. Immediately postprocedure, the patient developed subcutaneous emphysema and bilateral pneumothoraces. Further imaging revealed the presence of free intra-abdominal air. The patient made a very quick recovery after bilateral chest drain insertion and no further intervention was required. We propose that pneumothorax, pneumomediastinum, and subcutaneous emphysema during ERCP, in the absence of duodenal perforation may be explained by leakage of air from a site of low resistance such as the sphincterotomy site, or as a result of copious Valsalva manoeuvres performed by a patient tolerating the procedure poorly

New thiophene-based conjugated macrocycles for optoelectronic applications

GC acknowledges the EPSRC for funding (EP/E036244/1). JMS acknowledges the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 for PhD funding. JMS also acknowledges Dr Nor Basid Adiwibawa Prasetya for helpful advice. Dr L. K. Jagadamma acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (European Commission) (MCIF: No. 745776).Thiophene-based semiconductors are amongst the most successful materials in organic electronics. In this contribution, we present the synthesis and characterisation of two thiophene-based macrocycles as well as their evaluation in organic-electronic devices. McT-1 is composed of ten thiophene moieties, whereas in McT-2, four additional electron-deficient benzothiadiazole moieties are incorporated to form a donor–acceptor (D–A) π-system. Red-shifted and broadened absorption spectra as well as more positive redox potentials are observed in McT-2, whereas McT-1 displays a sharper absorption band with a higher extinction coefficient. Macrocycle McT-1 shows emission in the yellow region whereas McT-2 displays emission in the red wavelength region. DFT calculations predict the macrocycles to comprise of mainly the E,E isomers with a near-planar structure, which is further supported by the single crystal X-ray structure for McT-1. Their charge transporting properties are determined by fabricating thin-film OFETs. The photovoltaic properties of McT-1 and McT-2 are also investigated by fabricating bulk heterojunction (BHJ) devices and their potential as photodetectors has been evaluated.Publisher PDFPeer reviewe