Synthesis of highly functionalised tetrathiafulvalenes

A range of functionalised symmetrical and unsymmetrical tetrathiafulvalene (TTF) derivatives containing substituted 4,5-(propylene- 1,3-dithio) units fused to the TTF framework has been prepared. In particular, TTF derivatives bearing hydroxy or ketone functionality have been obtained. Cyclic voltammetric studies establish that the new TTF derivatives are efficient π-electron donors; they undergo two reversible, single-electron redox waves. A series of new bis- and tris-tetrathiafulvalene derivatives has been prepared. The TTF-thiolate anion has been used as a key intermediate and shown to be a particularly versatile reagent for this purpose. 4-(Benzoylthio) tetrathiafulvalene has been prepared and serves as a convenient shelf-stable precursor of the TTF-thiolate anion. A novel pentakis-tetrathiafulvalene macromolecule has been efficiently synthesised. The solution electrochemistry of the new multi-TTF derivatives has been studied by cyclic voltammetry, which reveals that the TTF moieties do not interact to any significant extent. Methodology has been developed for the preparation of highly functionalised analogues of TTF containing the 9,10-bis(l,3-dithiol-2- ylidene)-9,l 0-dihydroanthracene unit. These are versatile electron donor systems and have been used in the construction of novel redox assemblies

Identification and comparative analysis of components from the signal recognition particle in protozoa and fungi

BACKGROUND: The signal recognition particle (SRP) is a ribonucleoprotein complex responsible for targeting proteins to the ER membrane. The SRP of metazoans is well characterized and composed of an RNA molecule and six polypeptides. The particle is organized into the S and Alu domains. The Alu domain has a translational arrest function and consists of the SRP9 and SRP14 proteins bound to the terminal regions of the SRP RNA. So far, our understanding of the SRP and its evolution in lower eukaryotes such as protozoa and yeasts has been limited. However, genome sequences of such organisms have recently become available, and we have now analyzed this information with respect to genes encoding SRP components. RESULTS: A number of SRP RNA and SRP protein genes were identified by an analysis of genomes of protozoa and fungi. The sequences and secondary structures of the Alu portion of the RNA were found to be highly variable. Furthermore, proteins SRP9/14 appeared to be absent in certain species. Comparative analysis of the SRP RNAs from different Saccharomyces species resulted in models which contain features shared between all SRP RNAs, but also a new secondary structure element in SRP RNA helix 5. Protein SRP21, previously thought to be present only in Saccharomyces, was shown to be a constituent of additional fungal genomes. Furthermore, SRP21 was found to be related to metazoan and plant SRP9, suggesting that the two proteins are functionally related. CONCLUSIONS: Analysis of a number of not previously annotated SRP components show that the SRP Alu domain is subject to a more rapid evolution than the other parts of the molecule. For instance, the RNA portion is highly variable and the protein SRP9 seems to have evolved into the SRP21 protein in fungi. In addition, we identified a secondary structure element in the Sacccharomyces RNA that has been inserted close to the Alu region. Together, these results provide important clues as to the structure, function and evolution of SRP

A family of unsymmetrical hydroxyl-substituted BEDT-TTF donors: syntheses, structures and preliminary thin film studies

Three new unsymmetrical hydroxyl-functionalized donors H1–H3 closely related to hydroxymethyl-BEDT-TTF have been synthesised and characterised. Cyclic voltammetry studies showed that the compounds exhibit reversible two one-electron redox processes typical for BEDT-TTF derivatives. X-ray diffraction studies of H1 and H2 reveal π-stacking interactions between pairs of donors that are organized into distinct H-bonded square motifs and DFT calculations indicate that the HOMO is located on the central 1,3-dithiole rings. Protection of the hydroxyl group with acetyl in 13 eliminates co-facial S...S interactions between the dimers to accommodate the bulkier side chains, but short edge-to-edge S...S contacts offer an alternative pathway for electron mobility. Chemical oxidation of H1 and HMET 2 with I2 afforded single crystals of two 1 : 1 charge transfer salts, 18 and 19. The molecules pack as dimers with close π-stacking interactions between pairs of radical cations whose crystal structures are further stabilized via an interplay of S...S and S...I contacts. Iodine-doped surface conducting polystyrene blend films of H3 deposited on a silica substrate exhibit quasiconducting properties, but afford no OFET response when fabricated into devices. Visible-NIR studies of a doped polystyrene blend film of H3 cast on a glass substrate show absorption bands at λ =9 50 and 3000 nm, consistent with mixed valence states due to the presence of charge-transfer species on the surface of the films