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Updated: Apr 28, 2026

Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly
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Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly

Published on: February 6, 2020

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评论"在合成异构体系统中激发状态之间的工程连贯性"

Alexei Halpin1, Philip J M Johnson1, R J Dwayne Miller2

  • 1Institute for Optical Sciences and Departments of Chemistry and Physics, University of Toronto, 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada.

Science (New York, N.Y.)
|June 7, 2014
PubMed
概括

这项研究质疑分子异构体中电子连贯性的解释. 实验的不一致性表明,观察到的动态可能无法可靠地归因于长时间的连贯性.

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Stereoisomerism02:52

Stereoisomerism

Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
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The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
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Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
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