- N -Alkyl substituted 1 H -benzimidazoles as improved n-type dopants for a naphthalene-diimide based copolymer
-
Doped polymer semiconductors are actively studied for opto- and micro-electronic applications including thermoelectric generators, where a high electrical conductivity is a key factor. In general, n-type doping is more challenging to achieve than p-type doping. Here we study n-type doping of a commonly used electron transporting naphthalene-diimide bithiophene copolymer with a series of air-stable and solution-processable benzimidazole dopants. To understand the role of dopant structure on miscibility and the resulting conductivity, benzimidazoles with different linear and branched alkyl substituents were synthesized, and their doping efficacy compared through combined morphological, electrical and thermoelectric characterization. We observe a clear dependence of the nature of the alkyl substituent on dopant intercalation into the semicrystalline morphology. By increasing the length or the steric hindrance of the alkyl substituents, the miscibility between dopant and copolymer is enhanced leading to optimized electrical conductivity.
- Saglio,Mura,Massetti,Scuratti,Beretta,Jiao,McNeill,Sommer,Famulari,Lanzani,Caironi,Bertarelli
-
-
Read Online
- Repurposing Triphenylmethane Dyes to Bind to Trimers Derived from Aβ
-
Soluble oligomers of the β-amyloid peptide, Aβ, are associated with the progression of Alzheimer's disease. Although many small molecules bind to these assemblies, the details of how these molecules interact with Aβ oligomers remain unknown. This paper reports that crystal violet, and other C3 symmetric triphenylmethane dyes, bind to C3 symmetric trimers derived from Aβ17-36. Binding changes the color of the dyes from purple to blue, and causes them to fluoresce red when irradiated with green light. Job plot and analytical ultracentrifugation experiments reveal that two trimers complex with one dye molecule. Studies with several triphenylmethane dyes reveal that three N,N-dialkylamino substituents are required for complexation. Several mutant trimers, in which Phe19, Phe20, and Ile31 were mutated to cyclohexylalanine, valine, and cyclohexylglycine, were prepared to probe the triphenylmethane dye binding site. Size exclusion chromatography, SDS-PAGE, and X-ray crystallographic studies demonstrate that these mutations do not impact the structure or assembly of the triangular trimer. Fluorescence spectroscopy and analytical ultracentrifugation experiments reveal that the dye packs against an aromatic surface formed by the Phe20 side chains and is clasped by the Ile31 side chains. Docking and molecular modeling provide a working model of the complex in which the triphenylmethane dye is sandwiched between two triangular trimers. Collectively, these findings demonstrate that the X-ray crystallographic structures of triangular trimers derived from Aβ can be used to guide the discovery of ligands that bind to soluble oligomers derived from Aβ.
- Salveson, Patrick J.,Haerianardakani, Sepehr,Thuy-Boun, Alexander,Yoo, Stan,Kreutzer, Adam G.,Demeler, Borries,Nowick, James S.
-
-
Read Online
- New experiments in the reductive N-alkylation and N-peralkylation of aromatic amines
-
Some secondary and primary aromatic amines were variously N-alkylated and N-peralkylated by the aldehyde-sodium borohydride procedure in acidic aqueous solution. The procedure lends itself to the α-mono and α,α1-dideuterium labelling of the new N-substituent(s).
- Verardo,Giumanini,Strazzolini
-
p. 609 - 627
(2007/10/02)
-