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Related Concept Videos

Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

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
Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
Woodward–Hoffmann Selection Rules and Microscopic Reversibility01:34

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...

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Related Experiment Video

Updated: Jun 4, 2026

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
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The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Published on: April 10, 2015

Energy transfer pathways in a rylene-based Triad.

Eduard Fron1, Larissa Puhl, Ingo Oesterling

  • 1Department of Chemistry and Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium.

Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry
|February 24, 2011
PubMed
Summary
This summary is machine-generated.

This study demonstrates efficient light harvesting and energy transfer in a novel Triad molecule. Excitation energy cascades from naphthalenemonoimide to perylenediimide and finally to the terrylenediimide core, showcasing its potential in light-collecting applications.

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Area of Science:

  • Photochemistry and Materials Science
  • Supramolecular Chemistry
  • Energy Transfer Dynamics

Background:

  • Developing efficient light-harvesting systems is crucial for advanced optical and electronic devices.
  • Understanding excitation energy migration pathways in complex molecular architectures is key to optimizing performance.

Purpose of the Study:

  • To investigate the excitation energy migration and excited-state dynamics in a newly synthesized Triad molecule.
  • To characterize the light-collecting efficiency and fluorescence properties of the Triad.
  • To elucidate the energy transfer mechanisms from peripheral chromophores to the central core.

Main Methods:

  • Steady-state and femtosecond/picosecond time-resolved spectroscopy in solution.
  • Single-molecule confocal microscopy.
  • Photobleaching studies of single Triad molecules in PMMA films under ambient and nitrogen atmospheres.

Main Results:

  • The Triad acts as an efficient light collector across the visible spectrum, with fluorescence primarily from the terrylenediimide core (60% quantum yield).
  • Selective excitation of naphthalenemonoimide chromophores leads to cascade energy transfer via perylenediimide to the terrylenediimide core (<200 fs and 3.7 ps).
  • Direct energy transfer pathways from naphthalenemonoimide to terrylenediimide were observed (1.5 ps and 8.4 ps), supported by single-molecule emission and photobleaching experiments.

Conclusions:

  • The synthesized Triad exhibits efficient cascade energy transfer, making it a promising light-harvesting material.
  • The observed energy transfer pathways are influenced by the molecular architecture and environmental conditions (e.g., oxygen presence).
  • Single-molecule studies provide direct evidence for the proposed energy transfer mechanisms and photostability under different conditions.