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Isomeric Dithienophosphepines: The Impact of Ring Fusion on Electronic and Structural Properties.

ABSTRACT: The synthesis and extensive experimental (X-ray crystallography, UV/Vis spectroscopy, cyclic voltammetry) and theoretical (DFT calculations) characterization of two isomeric dithieno[b,f]phosphepines (DTPs) are presented herein. The relative orientation of the phosphepine and the thiophene moieties has a decisive impact on the electronic and structural properties of these compounds. Moreover, the thiophene units allow for a facile subsequent functionalization through direct Pd-catalyzed C-H coupling, which renders DTPs highly promising building blocks for organophosphorus functional materials.

SUBMITTER: Padberg K

PROVIDER: S-EPMC7154744 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Isomeric Dithienophosphepines: The Impact of Ring Fusion on Electronic and Structural Properties.

Padberg Kevin K Ascherl Johannes D R JDR Hampel Frank F Kivala Milan M

Chemistry (Weinheim an der Bergstrasse, Germany) 20200130 16

The synthesis and extensive experimental (X-ray crystallography, UV/Vis spectroscopy, cyclic voltammetry) and theoretical (DFT calculations) characterization of two isomeric dithieno[b,f]phosphepines (DTPs) are presented herein. The relative orientation of the phosphepine and the thiophene moieties has a decisive impact on the electronic and structural properties of these compounds. Moreover, the thiophene units allow for a facile subsequent functionalization through direct Pd-catalyzed C-H coup ...[more]

PMID: 31797440

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Project description:Diketopyrrolopyrroles (DPP) have been recognized as a promising acceptor unit for construction of semiconducting donor-acceptor (D-A) polymers, which are typically flanked by spacers such as thiophene rings via a carbon-carbon single bond formation. It may suffer from a decrease in the coplanarity of the molecules especially when bulky side chains are installed. In this work, the two N atoms in the DPP unit are further fused with C-3 of the two flanking thiophene rings, yielding a π-expanded, very planar fused-ring building block (DPPFu). A novel DPPFu-based D-A copolymer (PBDTT-DPPFu) was successfully synthesized, consisting of a benzo[1,2-b:4,5-b']dithiophene (BDTT) unit as a donor and a DPPFu unit as an acceptor. For comparison, the unfused DPP-based counterpart PBDTT-DPP was also synthesized. Two dodecyl alkyl chains were attached to thiophene rings of DPP moieties to ensure good solubility of the DPPFu-based polymer. The influence of the ring-fusion effect on their structure, photophysical properties, electronic properties, molecular packing, and charge transport properties is investigated. Ring-fusion enhances the intermolecular interactions of PBDTT-DPPFu polymer chains as indicated by density functional theory calculation and analysis of electrostatic potential and van der Waals potential and results in significantly improved molecular packing for both the in-plane and out-of-plane directions as suggested by X-ray measurements. Finally, we correlate the molecular packing to the device performance by fabricating field-effect transistors based on these two polymers. The charge carrier mobility of the ring-fused polymer PBDTT-DPPFu is significantly higher as compared to the PBDTT-DPP polymer without ring-fusion, although PBDTT-DPPFu exhibited a much lower number-average molecular weight of 17 kDa as compared to PBDTT-DPP with a molecular weight of 108 kDa. The results from our comparative study provide a robust way to increase the interchain interaction by ring-fusion-promoted coplanarity.

Project description:While the importance of viral fusion peptides (e.g., hemagglutinin (HA) and gp41) in virus-cell membrane fusion is established, it is unclear how these peptides enhance membrane fusion, especially at low peptide/lipid ratios for which the peptides are not lytic. We assayed wild-type HA fusion peptide and two mutants, G1E and G13L, for their effects on the bilayer structure of 1,2-dioleoyl-3-sn-phosphatidylcholine/1,2-dioleoyl-3-sn-phosphatidylethanolamine/Sphingomyelin/Cholesterol (35:30:15:20) membranes, their structures in the lipid bilayer, and their effects on membrane fusion. All peptides bound to highly curved vesicles, but fusion was triggered only in the presence of poly(ethylene glycol). At low (1:200) peptide/lipid ratios, wild-type peptide enhanced remarkably the extent of content mixing and leakage along with the rate constants for these processes, and significantly enhanced the bilayer interior packing and filled the membrane free volume. The mutants caused no change in contents mixing or interior packing. Circular dichroism, polarized-attenuated total-internal-reflection Fourier-transform infrared spectroscopy measurements, and membrane perturbation measurements all conform to the inverted-V model for the structure of wild-type HA peptide. Similar measurements suggest that the G13L mutant adopts a less helical conformation in which the N-terminus moves closer to the bilayer interface, thus disrupting the V-structure. The G1E peptide barely perturbs the bilayer and may locate slightly above the interface. Fusion measurements suggest that the wild-type peptide promotes conversion of the stalk to an expanded trans-membrane contact intermediate through its ability to occupy hydrophobic space in a trans-membrane contact structure. While wild-type peptide increases the rate of initial intermediate and final pore formation, our results do not speak to the mechanisms for these effects, but they do leave open the possibility that it stabilizes the transition states for these events.

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Isomeric Dithienophosphepines: The Impact of Ring Fusion on Electronic and Structural Properties.

Publications

Isomeric Dithienophosphepines: The Impact of Ring Fusion on Electronic and Structural Properties.

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