Functionalised tetraheterofulvalenes for conducting landmuir-blodgett films and charge-transfer complexes

The tetrathiafulvalene (TTF) mono-anion route to functionalised derivatives has been extended to lead to new materials for charge-transfer (CT) complexes. New improved routes have been established towards halogenated and chalcogenated TTF derivatives from the TTF anion (23). Highly conducting complexes with TCNQ (1) have been obtained from 4-chloro- (30) and 4-bromotetrathiafulvalene (32). X-Ray studies of ethylenediseleno-TTF (44) and bis(tetrathiafulvalenyl)sulphide (59) have revealed novel structural features. New long chain TTF materials have also been synthesised, suitable for Langmuir-Blodgett (LB) films, using TTF anion and 1,3-dithiole cross-coupling methodologies. Amphiphiles bearing highly functionalised groups, both adjacent to the TTF ring and in the side chain, have been synthesised, and LB films have been formed from some of these materials. Iodine doping of the films has provided conducting mixed- valence systems. Monofunctionalised tetraselenafulvalenes (TSF) have been synthesised from the TSF tetra-anion (118) and a range of acid chlorides, to yield the corresponding ketones. X-Ray crystal structure analysis of 4-acetyltetraselenafulvalene (123), has unequivocally proven that under these reaction conditions the TSF unit stays intact

A water-soluble supramolecular polymeric dual sensor for temperature and pH with an associated direct visible readout

We report a multi-stimuli responsive polymeric sensor consisting of a pseudorotaxane-like architecture fabricated from a 1,5-diaminonaphthalene end-functionalized poly(N-isopropyl)acrylamide (Napht-N-PNIPAM) and cyclobis(paraquat-p-phenylene) (CBPQT4+,4Cl-). The coloured nature of the poly-pseudorotaxane provides a sensor for temperature and pH in water with an associated visible readout. To create this dual responsive polymeric sensor, a new chain transfer agent (Napht-N-CTA) incorporating a pH-responsive 1,5-diaminonaphthalene unit was synthesized and used for the polymerization of N-isopropylacrylamide via Reversible Addition-Fragmentation Chain Transfer (RAFT). The ability of Napht-N-PNIPAM to form a pseudorotaxane architecture with CBPQT4+,4Cl- in aqueous media was studied by means of UV-Vis, NMR (1H, 2D-ROESY, DOSY) and ITC experiments. Interestingly, the pseudorotaxane architecture can be reversibly dissociated upon either heating the sample above its cloud point or protonating the nitrogen atoms of the 1,5-diaminonaphthalene-based guest unit by adjusting the pH to around 1. ln both cases a dramatic colour change occurs from intense blue-green to colourless

Synthesis and Characterization of Naphthalenediimide-Functionalized Flavin Derivatives

Two acceptor–acceptor dyads have been synthesized featuring a flavin moiety and a naphthalenediimide (NDI) unit. The NDI unit is linked to the flavin through a short spacer group via either the N(3) or N(10) positions of the flavin. We have investigated the UV-Vis and redox properties of these multi-electron accepting systems which indicate that these materials display the collective properties of their component systems. Fluorescence spectroscopy measurements have revealed that their emission properties are dominated by the flavin unit

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

Supramolecular polymer hydrogels induced by host-guest interactions with di-[cyclobis(paraquat-p-phenylene)] cross-linkers: from molecular complexation to viscoelastic properties

Supramolecular polymer networks have been designed on the basis of a -electron donor/acceptor complex: naphthalene (N)/cyclobis(paraquat-p-phenylene) (CBPQT4+=B). For this purpose, a copolymer of N,N-dimethylacrylamide P(DMA-N1), lightly decorated with 1 mol% of naphthalene pendant groups, has been studied in semi-dilute un-entangled solution in the presence of di-CBPQT4+ (BB) crosslinker type molecules. While calorimetric experiments demonstrate the quantitative binding between N and B groups up to 60 °C, the introduction of BB crosslinkers into the polymer solution gives rise to gel formation above the overlap concentration. From a comprehensive investigation of viscoelastic properties, performed at different concentrations, host/guest stoichiometric ratios and temperatures, the supramolecular hydrogels are shown to follow a Maxwellian behavior with a strong correlation of the plateau modulus and the relaxation time with the effective amount of interchain cross-linkers and their dissociation dynamics, respectively. The calculation of the dissociation rate constant of the supramolecular complex, by extrapolation of the relaxation time of the network back to the beginning of the gel regime, is discussed in the framework of theoretical and experimental works on associating polymers

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

An investigation of the roles furan versus thiophene π-bridges play in donor–π-acceptor porphyrin based DSSCs

Dye-sensitized solar cells (DSSCs) continue to attract interest due to their lower cost production compared to silicon based solar cells and their improving power conversion efficiencies. Porphyrin-based sensitizers have become an important sub-class due to their strong absorption characteristics in the visible region, convenient modulation of properties through synthetic manipulation and class-leading power conversion efficiencies. In this article, we report the synthesis and characterization of two porphyrin-based dyes and their application as sensitizers in DSSCs. A thiophene and a furan moiety have been incorporated into the push–pull architecture as a π-bridge, allowing the systematic investigation of how these moieties influence the physical properties of the dyes and the performance of their resulting DSSCs. A significant difference in PCEs has been observed, with the furan containing dye (PorF, PCE = 4.5%) being more efficient than the thiophene-based analogue (PorT, PCE = 3.6%) in conjunction with the iodide/triiodide redox electrolyte

The ‘Engineering First Year’: Step Up To Success

The nuanced nature of engineering as a profession is highlighted in a recent statement by the EPC (2023) in response to the UCAS publication ‘The Future of Undergraduate Admissions’ (2023). Focusing on the value of Personal Statements within the University Selection System, the EPC asks UCAS to provide more practical information to prospective students about the nature of engineering and what prerequisite qualifications are needed to study engineering. Such clarity is particularly important when considering Engineering Degree Apprentices. Starting with the research question “How can the gap between school and university be bridged in engineering education?” the paper critically discusses a project currently being undertaken by a multi-disciplinary team of colleagues working together to enhance the student experience. Located in one the UK’s largest Engineering Education Departments, the “Step Up” Project analyses the barriers and drivers to engineering education faced by first-year Degree Apprenticeship students from three distinctive engineering and computing science disciplines. This paper represents a small part of a much larger project where the student experience is being prioritised and high-quality learning and teaching is expected. The paper is built upon the emergent findings of a three focus groups with engineering degree apprentices. Whilst the findings are relevant to all years of study, the recommendations and conclusion highlight the importance of ‘getting the first year right’ and empowering students to ‘step up to success’ in university and in work. This evidences a demand for clearer explanations of the knowledge and skills expected of incoming students

Enhanced exciton harvesting in a planar heterojunction organic photovoltaic device by solvent vapor annealing

The singlet exciton diffusion length was measured in a small molecule electron donor material DR3TBDTT using fluorescence quenching at a planar interface with a cross-linked fullerene derivative. The one-dimensional exciton diffusion length was increased from ~16 to ~24 nm by annealing the film in carbon disulfide solvent vapor. Planar heterojunction solar cells were fabricated using bilayers of these materials and it was found that solvent vapor annealing increased the short circuit current density by 46%. This can be explained by improved exciton harvesting in the annealed bilayer