Related Experiment Video
Updated: Jul 12, 2026
07:50
Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization
Published on: July 17, 2015
Two-dimensional electronic conjugation: cooperative folding and fluorescence switching
Xuan Jiang1, John C Bollinger, Dongwhan Lee
1Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
Journal of the American Chemical Society
|September 7, 2006
Summary
Researchers developed shape-adaptive molecules that change conformation by controlling hydrogen bonds. Their fluorescence efficiency was enhanced by rigidifying the molecular core, enabling reversible responses to external signals.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Photophysics
Background:
- C3-symmetric molecules derived from tris(N-salicylideneamine) exhibit conformational flexibility.
- Hydrogen bonding networks play a crucial role in molecular organization and switching.
- Emission properties of molecular systems are sensitive to structural changes.
Purpose of the Study:
- To investigate the conformational switching of C3-symmetric molecules.
- To explore the relationship between hydrogen bonding and molecular conformation.
- To understand how structural modifications affect fluorescence properties.
Main Methods:
- Synthesis of tris(N-salicylideneamine)-derived C3-symmetric molecules.
- Analysis of hydrogen bonding networks using spectroscopic techniques.
- Investigation of conformational changes induced by external stimuli.
- Measurement of fluorescence efficiency and its response to structural modifications.
Main Results:
- Conformational switching was successfully driven by organizing and disrupting hydrogen bonding networks.
- The emission properties of the shape-adaptive constructs showed reversible responses to external signals.
- Structural rigidification of the [pi,pi]/[n,pi]-conjugated molecular core led to significant enhancement in fluorescence efficiency.
Conclusions:
- Hydrogen bonding networks are effective triggers for conformational switching in C3-symmetric molecules.
- These molecular constructs exhibit tunable and reversible emission properties.
- Rigidification strategies can be employed to optimize fluorescence efficiency in shape-adaptive materials.
Related Concept Videos
01:12Two-Dimensional (2D) NMR: Overview
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
01:27π Electron Effects on Chemical Shift: Overview
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0, resulting in...
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
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...
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...
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
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...
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...
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this process,...
01:30The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...