The experimental investigation of side-chain effects on intramolecular charge transport in π-conjugated molecules is essential but remains challenging. Herein, the dependence of intra-molecular conductance on the nature of branching alkyl chains is investigated through a combination of the scanning tunneling microscope break junction (STM-BJ) technique and density functional theory. Three thiophene-flanked diketopyrrolopyrrole (DPP) derivatives with different branching alkyl chains (isopentane, 3-methylheptane, and 9-methylnonadecane) are used with phenylthiomethyl groups as the anchoring groups. The results of single-molecule conductance measurements show that as the alkyl chain becomes longer, the torsional angles between the aromatic rings increase due to steric crowding, and therefore, the molecular conductance of DPP decreases due to reduction in conjugation. Both theoretical simulations and H NMR spectra demonstrate that the planarity of the DPPs is directly reduced after introducing longer branching alkyl chains, which leads to a reduced conductance. This work indicates that the effect of the insulating side chain on the single-molecule conductance cannot be neglected, which should be considered for the design of future organic semiconducting materials.
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http://dx.doi.org/10.1002/cphc.202100634 | DOI Listing |
Int J Biol Macromol
December 2024
School of Textile Science and Engineering, Xi'an Polytechnic University, Xi'an 710048, Shaanxi, China; Key Laboratory of Functional Textile Material and Product, Xi'an Polytechnic University, Ministry of Education, Xi'an 710048, Shaanxi, China. Electronic address:
We provided an efficient method for preparing fluorescent materials with high specificity. Firstly, the cellulose-based aggregations with adjustable morphologies and sizes were obtained by cross-linking copolymerization and self-assembly. Then, after encapsulating the fluorescein isothiocyanate (FITC) into the hydrophobic microregions of the cellulose-based aggregations by ultrasound/dialysis method, a series of cellulose-based fluorescent aggregations with different morphologies was obtained.
View Article and Find Full Text PDFJ Transl Med
December 2024
Department of Orthopaedic Surgery, The First Affiliated Hospital of Harbin Medical University, 2075 Qunli Seventh Avenue, Daoli District, Harbin, 150001, Heilongjiang Province, China.
Background: Spinal cord injury (SCI) inflicts a severe burden on patients and lacks effective treatments. Owing to the poor regenerative capabilities of endogenous oligodendrocyte precursor cells (OPCs) following SCI, there is a growing interest in alternative sources, such as human umbilical cord mesenchymal stem cells (HUCMSCs). TET3 is a key DNA demethylase that plays an important role in neural differentiation, but its role in OPC formation is not well understood.
View Article and Find Full Text PDFJ Chromatogr A
December 2024
Restek Corporation, 110 Benner Circle, Bellefonte, PA, 16823, USA. Electronic address:
The chemical structure of nine imidazolium sulfonate and triflimide zwitterionic liquids (ZILs) were systematically tuned to increase their thermal stability for gas chromatography (GC) separations. Substituents for imidazolium and 2-phenylimidazolium cation systems, comprised of alkyl, benzyl, and oligoether groups of varying chain lengths, were studied as stationary phases in GC. Propanesulfonate, ethanesulfonate, and propanetriflimide anions were examined to understand the effect of linker length and nucleophilicity on ZIL thermal stability.
View Article and Find Full Text PDFJ Nanobiotechnology
December 2024
Institute of Combined Injury, National Key Laboratory of Trauma and Chemical Poisoning, Army Key Laboratory of Nanomedicine, Department of Military Preventive Medicine, Army Medical University (Third Military Medical University), Chongqing, 400038, China.
Enhancing the sensitivity of radiotherapy (RT) towards renal cell carcinoma (RCC) remains a challenge because RCC is a radioresistant tumor. In this work, we design and report asymmetrically Polyethylene Glycol (PEG)ylated and amphipathic heptamethine indocyanine dyes for efficient radiosensitization of RCC treatment. They were synthesized by modifying different lengths of PEG chains as hydrophilic moieties on one N-alkyl chain of a mitochondria-targeting heptamethine indocyanine dye (IR-808), and a radiosensitizer 2-nitroimidazole (NM) as a hydrophobic moiety on another N-alkyl chain.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, U.K.
The catalytic competency of the ribosome in extant protein biosynthesis is thought to arise primarily from two sources: an ability to precisely juxtapose the termini of two key substrates─3'-aminoacyl and -acyl-aminoacyl tRNAs─and an ability to ease direct transpeptidation by their desolvation and encapsulation. In the absence of ribosomal, or enzymatic, protection, however, these activated alkyl esters undergo efficient hydrolysis, while significant entropic barriers serve to hamper their intermolecular cross-aminolysis in bulk water. Given that the spontaneous emergence of a catalyst of comparable size and sophistication to the ribosome in a prebiotic RNA world would appear implausible, it is thus natural to ask how appreciable peptide formation could have occurred with such substrates in bulk water without the aid of advanced ribozymatic catalysis.
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