Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
2.2K
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
Selection Rules: Photochemical Activation
2.2K
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
7.2K
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
7.2K
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
12.6K
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
12.6K
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
12.1K
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
12.1K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.5K
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.
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.
2.5K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
3.0K
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.
3.0K
You might also read
Related Articles
Articles linked to this work by shared authors, journal, and citation graph.
Sort by
Same author
Hybrid Carbon Nitride/Cobalt Phthalocyanine Nanocomposites for Efficient Photocatalytic Hydrogen Generation.
ACS applied energy materials·2026
Same author
Ultrafast charge dynamics of diketopyrrolopyrrole-based terpolymers for optoelectronic applications: impact of acceptor concentrations and thermal annealing.
Nanoscale·2026
Same author
Molecular Dioxygen-Mediated Passivation of Electron Traps in n-Type Organic Charge-Transfer Complexes.
Angewandte Chemie (International ed. in English)·2026
Same author
Trapped Cycloadducts of 1-Azabutadienes via Microwave-Assisted Ring Opening of <i>N</i>-Acyl-2-azetines.
The Journal of organic chemistry·2026
Same author
Impacting the balance between CO<sub>2</sub> and proton reduction by control over aggregation in a model π-conjugated N-heterocycle - proflavine.
Chemical science·2026
Same author
Langmuir-Blodgett Assembly of PM6 and N2200 Polymer Planar Heterojunctions for Interfacial Probing.
Langmuir : the ACS journal of surfaces and colloids·2026
Same journal
A Multifaceted Vision of Challenges and Opportunities in Practical Artificial Photosynthesis Devices.
Artificial photosynthesis (Washington, D.C.)·2026
Same journal
Efficient and Robust Hybrid Molecular Photoanodes for Water Oxidation at Neutral pH Based on Ru Complexes Covalently Bonded to Polymeric Carbon Nitride.
Artificial photosynthesis (Washington, D.C.)·2026
Same journal
Axiomatic Design for Analysis and Noniterative Engineering of Photoelectrochemical Cells for CO<sub>2</sub> Conversion at High Photon to Product Yield.
Artificial photosynthesis (Washington, D.C.)·2025
Same journal
Tuning the Photocatalytic CO<sub>2</sub> Reduction through <i>para</i>-Substituents in Bipyridyl Rhenium Complexes.
Artificial photosynthesis (Washington, D.C.)·2025
Same journal
Demonstration of the Radical Coupling Pathway in a Fast Fe-Based Water Oxidation Catalyst.
Artificial photosynthesis (Washington, D.C.)·2025
Same journal
Unidirectional Transmembrane Photoinduced Electron Transfer with Artificial Metallopeptides.
Artificial photosynthesis (Washington, D.C.)·2025
Related Experiment Video
Updated: Jan 16, 2026
14:11
Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
6.7K
Oxygen-Mediated Sequential Down-Conversion in Perylenediimides.
Yifan Bo1, Nathalie Zink-Lorre2, René Weiß1
1Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), FAU Profile Center Solar, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany.
Artificial Photosynthesis (Washington, D.C.)
|October 2, 2025
Summary
Perylenediimides (PDIs) generate two singlet oxygen molecules per photoexcitation in oxygen-rich environments. This sequential down-conversion process is crucial for understanding PDI photophysics and optoelectronic applications.
More Related Videos
08:51Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core
Published on: October 24, 2017
10.0K
05:48Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
8.6K
Area of Science:
- Photochemistry
- Materials Science
- Organic Electronics
Background:
- Perylenediimides (PDIs) are vital chromophores in optoelectronics.
- Their photophysical behavior in oxygen-rich conditions is not well understood.
Purpose of the Study:
- To investigate the photophysics of PDI derivatives in varying oxygen concentrations.
- To elucidate the mechanism of oxygen-mediated sequential down-conversion in PDIs.
Main Methods:
- Steady-state and time-resolved absorption and emission spectroscopy.
- Experiments conducted in toluene with controlled oxygen levels.
- Analysis of three distinct PDI derivatives.
Main Results:
- Unsubstituted PDI and a bay-substituted PDI derivative showed oxygen-mediated sequential down-conversion.
- Photoexcitation of PDIs generates singlet oxygen (1O2) via triplet states (T1) and molecular oxygen (3O2).
- One PDI singlet excited state (S1) can produce two 1O2 molecules, dependent on energy levels.
Conclusions:
- Demonstrated oxygen-mediated sequential down-conversion in PDI systems.
- Highlighted the critical role of energy transfer pathways and requirements for 1O2 generation.
- Provides insights into PDI photophysics for optoelectronic applications.