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Related Concept Videos

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
Variables Affecting Phosphorescence and Fluorescence01:26

Variables Affecting Phosphorescence and Fluorescence

Fluorescence and phosphorescence are essential phenomena in fields like analytical chemistry, biological imaging, and materials science, where they detect molecular properties and visualize cellular structures. Understanding the variables that influence these luminescent behaviors is crucial for maximizing accuracy and efficiency in their applications. These variables can broadly be grouped into chemical structure, solvent properties, and external conditions, each playing a distinct role in...
UV–Vis Spectroscopy of Conjugated Systems01:32

UV–Vis Spectroscopy of Conjugated Systems

Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
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.
Pericyclic Reactions: Introduction01:17

Pericyclic Reactions: Introduction

Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...

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Updated: Jun 20, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
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Published on: June 10, 2021

Geometric Evolution of Perylene-Based Intermolecular π-π Dimers Toward Static and Dynamic Multicolor Emission.

Zhou-An Xia1, Min Wu2, Yuxiang Dai3

  • 1State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China.

Angewandte Chemie (International Ed. in English)
|June 18, 2026
PubMed
Summary

Researchers designed a new organic solid capable of emitting multiple colors by controlling molecular arrangements. This breakthrough offers insights into creating advanced optical materials by tuning pi-pi interactions in dimers.

Keywords:
high pressureintelligent optical materialsperylene dimersthermochromic fluorescenceπ–π interactions

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Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera
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Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Published on: December 27, 2018

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Last Updated: Jun 20, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

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Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera
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Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Published on: December 27, 2018

Area of Science:

  • Materials Science
  • Organic Chemistry
  • Photophysics

Background:

  • Achieving controllable multicolor emission from single-molecule-based organic solids is challenging due to complex molecular packing.
  • Understanding and controlling intermolecular interactions, particularly pi-pi stacking, is crucial for tuning photophysical properties.

Purpose of the Study:

  • To design and synthesize a novel organic compound capable of exhibiting multicolor emission by precisely controlling pi-pi dimer geometries.
  • To investigate the relationship between molecular packing, intermolecular interactions, and emission color in organic solids.
  • To explore the potential for developing intelligent optical materials through polymorphism, piezochromism, and thermochromism.

Main Methods:

  • Synthesis of 3-(4-(1,2,2-triphenylvinyl)phenyl)perylene (pTPE-PE), integrating a perylene (PE) core with a tetraphenyl ethylene (TPE) substituent.
  • Crystallization of pTPE-PE to obtain multiple polymorphs with distinct emission colors.
  • Investigation of pressure-induced (piezochromism) and temperature-induced (thermochromism) emission changes.
  • Analysis of pi-pi stacking interactions, interplanar distances, and overlap ratios within the dimers.

Main Results:

  • pTPE-PE crystallization yielded four polymorphs emitting green, yellow, orange, and red light, demonstrating static multicolor emission.
  • Emission color was directly correlated with pi-pi interactions: closer interplanar distances and larger overlap ratios resulted in red-shifted emission.
  • Dynamic multicolor transitions were observed: yellow to orange to red under pressure, and sky-blue to green to orange with thermal stimuli.
  • Polymorphism, piezochromism, and thermochromism provided experimental evidence for exciton modulation via the dimer model.

Conclusions:

  • Tailoring pi-pi dimer geometries is an effective strategy for achieving controllable multicolor emission in organic solids.
  • The designed pTPE-PE compound serves as a model system for understanding exciton modulation through supramolecular interactions.
  • This study offers valuable insights for the rational design of intelligent optical materials with tunable emission properties.