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Related Concept Videos

¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

2.5K
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.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
2.5K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.4K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
1.4K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

1.5K
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
1.5K
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.3K
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
1.3K
¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

1.7K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
1.7K
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

1.4K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.4K

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Updated: Dec 28, 2025

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
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Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

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Enhanced coupling through π-stacking in imidazole-based molecular junctions.

Tianren Fu1, Shanelle Smith2, María Camarasa-Gómez3

  • 1Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: cn37@columbia.edu ;

Chemical Science
|February 15, 2020
PubMed
Summary
This summary is machine-generated.

Imidazole-based π-π stacked dimers create efficient conductance pathways in single-molecule junctions. This study confirms imidazole

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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
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Area of Science:

  • Molecular electronics
  • Nanotechnology
  • Physical chemistry

Background:

  • Single-molecule junctions are crucial for nanoscale electronic devices.
  • Understanding charge transport mechanisms in molecular systems is essential.
  • Imidazole is a heterocyclic aromatic organic compound with potential applications in molecular electronics.

Purpose of the Study:

  • To investigate imidazole-based π-π stacked dimers as conductance pathways in single-molecule junctions.
  • To characterize the imidazole-gold contact and electron transport mechanisms.
  • To verify imidazole's capability as a Au-binding ligand for stable molecular junctions.

Main Methods:

  • Utilized scanning tunneling microscope-break junction (STM-BJ) technique for conductance measurements.
  • Employed density functional theory (DFT)-based calculations for theoretical analysis.
  • Calculated molecular junction transmission using non-equilibrium Green's function (NEGF) formalism.

Main Results:

  • Demonstrated that imidazole-based π-π stacked dimers form strong and efficient conductance pathways.
  • Showed exponential decay of conductance with increasing alkane length, indicating tunneling or super-exchange.
  • Revealed that π-π stacked imidazole dimers exhibit superior coupling compared to through-bond tunneling.

Conclusions:

  • Imidazole serves as an effective Au-binding ligand for constructing stable single- and π-stacked molecule junctions.
  • π-π stacking in imidazole dimers enhances electron transport efficiency in molecular junctions.
  • The study validates the use of imidazole in developing advanced molecular electronic components.