14 research outputs found

    Redox-Regulated Rotary Motion of a Bis(9-triptycyl)-TTFV System

    No full text
    A tetra­thia­fulvalene vinylogue (TTFV) unit was covalently linked to two benzyl­triptycene molecular rotors to form a molecular gearset. Dynamic NMR studies showed that reversible redox reactions at the TTFV central unit exerted regulation over the rotational properties of the 9-triptycyl rotors

    Tetrathiafulvalene Vinylogue–Fluorene Co-oligomers: Synthesis, Properties, and Supramoleclar Interactions with Carbon Nanotubes

    No full text
    A series of bis­(dithiafulvenyl)-end-capped fluorene derivatives was prepared and subjected to a one-pot iodine-promoted oxidative polymerization to yield π-conjugated co-oligomers containing tetrathiafulvalene vinylogue and fluorene repeat units. The resulting π-oligomers were characterized to take either acyclic or cyclic molecular structures, depending on the π-conjugation length of the monomer used for the polymerization. Electronic and electrochemical redox properties were examined by UV–vis spectroscopic and cyclic voltammetric analyses, while the supramolecular interactions of the π-oligomers with single-walled carbon nanotubes were investigated by UV–vis–NIR and Raman spectroscopy

    Selective and Reversible Noncovalent Functionalization of Single-Walled Carbon Nanotubes by a pH-Responsive Vinylogous Tetrathiafulvalene–Fluorene Copolymer

    No full text
    A vinylogous tetrathiafulvalene (TTFV) monomer was prepared and copolymerized with fluorene to give a conformationally switchable conjugated copolymer. This copolymer was shown to undergo a conformational change upon protonation with trifluoroacetic acid (TFA). When mixed with single-walled carbon nanotubes (SWNTs), this TTFV–fluorene copolymer exhibited strong interactions with the SWNT surface, leading to stable, concentrated nanotube dispersions in toluene. Photoluminescence excitation mapping indicated that the copolymer selectively disperses low-diameter SWNTs, as would be expected from its ability to form a tightly coiled conformation on the nanotube surface. Addition of TFA to the copolymer–SWNT dispersion resulted in a rapid conformational change and desorption of the polymer from the SWNT surface, resulting in precipitation of pure SWNTs that were completely free of polymer. Importantly, the nanotubes isolated after dispersion and release by the TTFV–fluorene copolymer were more pure than the original SWNTs that were initially dispersed

    Novel <i>ENAM</i> and <i>LAMB3</i> Mutations in Chinese Families with Hypoplastic Amelogenesis Imperfecta

    No full text
    <div><p>Amelogenesis imperfecta is a group of inherited diseases affecting the quality and quantity of dental enamel. To date, mutations in more than ten genes have been associated with non-syndromic amelogenesis imperfecta (AI). Among these, <i>ENAM</i> and <i>LAMB3</i> mutations are known to be parts of the etiology of hypoplastic AI in human cases. When both alleles of <i>LAMB3</i> are defective, it could cause junctional epidermolysis bullosa (JEB), while with only one mutant allele in the C-terminus of LAMB3, it could result in severe hypoplastic AI without skin fragility. We enrolled three Chinese families with hypoplastic autosomal-dominant AI. Despite the diagnosis falling into the same type, the characteristics of their enamel hypoplasia were different. Screening of <i>ENAM</i> and <i>LAMB3</i> genes was performed by direct sequencing of genomic DNA from blood samples. Disease-causing mutations were identified and perfectly segregated with the enamel defects in three families: a 19-bp insertion mutation in the exon 7 of <i>ENAM</i> (c.406_407insTCAAAAAAGCCGACCACAA, p.K136Ifs*16) in Family 1, a single-base deletion mutation in the exon 5 of <i>ENAM</i> (c. 139delA, p. M47Cfs*11) in Family 2, and a <i>LAMB3</i> nonsense mutation in the last exon (c.3466C>T, p.Q1156X) in Family 3. Our results suggest that heterozygous mutations in <i>ENAM</i> and <i>LAMB3</i> genes can cause hypoplastic AI with markedly different phenotypes in Chinese patients. And these findings extend the mutation spectrum of both genes and can be used for mutation screening of AI in the Chinese population.</p></div

    Clinical and mutation analysis of Family 1.

    No full text
    <p>(<b>A</b>) Pedigree of Family 1. Black dots indicate members recruited for this study. (<b>B</b>) Frontal clinical photograph of the 7.5-year-old proband. (<b>C</b>) Frontal clinical photograph of the proband's father. (<b>D, E</b>) <i>ENAM</i> exon 7 sequencing chromatogram of an unaffected family member (II:1) (D), and the proband (III:1) (E), revealed a 19-bp insertion mutation: c.406_407insTCAAAAAAGCCGACCACAA, p.K136IfsX*16. (<b>F</b>) Panoramic radiograph of the proband taken at the age of 6.5.</p

    The electron-density distribution of C-terminus of the wild-type and mutant LAMB3 protein after 180° rotation.

    No full text
    <p>After 180° rotation, the difference of the electron-density distribution between the wild-type and mutant LAMB3 protein is shown.</p

    TTFV-Based Molecular Tweezers and Macrocycles as Receptors for Fullerenes

    No full text
    Hybrids of tetrathiafulvalene vinylogues (TTFVs) and planar arenes were synthesized via the click reaction to form tweezer-like and macrocyclic structures. These compounds were investigated as receptors for fullerenes (C<sub>60</sub> and C<sub>70</sub>) by UV–vis absorption and fluorescence spectroscopy

    A Macrocyclization of 1,8-Bis(dithiafulvenyl)pyrenes

    No full text
    Dithiafulvenyl (DTF) end groups were linked to the 1 and 8 positions of a pyrene core directly or via phenylene bridges to afford redox-active pyrene derivatives. Upon oxidation, the 1,8-bis­(DTF)­pyrene underwent stepwise electron transfers to form radical cation and dication species, whereas the phenylene-extended bis­(DTF)­pyrene derivative was cyclized into a macrocyclic trimer through sequential DTF oxidative coupling reactions in solution and in the solid state. The structural, electronic, and supramolecular properties of the pyrene-based macrocycle were investigated using various spectroscopic techniques and molecular modeling studies

    Dispersion of Single-Walled Carbon Nanotubes with Oligo(<i>p</i>‑phenylene ethynylene)s: A DFT Study

    No full text
    Pure carbon nanotubes (CNT) and CNT–polymer composites have many useful properties, ranging from electrical conductivity to superior mechanical strength. However, the full potential of using CNTs as reinforcements (in a polymer matrix, for example) has been severely limited because of complications associated with the dispersion of CNTs. CNTs tend to entangle with each other, forming materials with properties that fall short of expectations. One of the effective ways of dispersing CNTs is the use of short π-conjugated oligomers like oligo­(<i>p</i>-phenylene ethynylene)­s (OPEs) as dispersants. In this study, we provide a comprehensive investigation of the interactions between single-walled CNTs (SWCNTs) and OPEs with two different end groups; aldehyde (ALD) and dithiafulvene (DTF). The hybrid B3LYP and the dispersion (D)- and/or the long-range (LR)-corrected density functional theory (DFT) methods such as B97D, wB97XD, and CAM-B3LYP with the 6-31G­(d) basis set are employed in obtaining electronic structure information (dipole moments and energy levels) for the gas-phase (single) oligomers and the (6,5) SWCNT and their combinations. In addition, the D- and/or LR-corrected DFT methods are used in determining binding energies and intermolecular distances for the OPE/SWCNT combinations. We focus on understanding the roles of oligomer’s end groups and side chains in the dispersion of SWCNTs. In agreement with the experimental observations, the electronic structure and the binding energy results show that OPE-DTF interacts more strongly with the SWCNT than OPE-ALD. This work also provides insight into why OPEs end-capped with DTFs are much more effective in the dispersion of CNTs than OPEs end-capped with ALDs. Furthermore, this computational analysis can be of use in choosing an appropriate D- and/or LR-corrected DFT method when studying properties of systems containing CNTs
    corecore