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Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes
Published on: April 1, 2013
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[2,2](5,8)Picenophanedienes: Syntheses, Structural Analyses, Molecular Dynamics, and Reversible Intramolecular
Min-Chih Tang1, Yu-Chen Wei2, Yen-Chen Chu1
1Department of Chemistry, National Cheng Kung University, 70101 Tainan, Taiwan.
Journal of the American Chemical Society
|November 19, 2020
Summary
Researchers developed an efficient synthesis for dibromophene derivatives, creating novel picenophanes. These molecules exhibit unique photophysical properties, including dual emission and excimer formation, influenced by structural variations.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Photophysics
Background:
- Picene derivatives are of interest due to their large π-systems.
- Understanding the structure-property relationships in complex polycyclic aromatic hydrocarbons is crucial.
Purpose of the Study:
- To develop an efficient synthetic route to functionalized picene precursors.
- To synthesize and characterize novel picenophane derivatives.
- To investigate the photophysical properties and conformational dynamics of these picenophanes.
Main Methods:
- Multigram scale synthesis of 5,8-dibromo-2,11-di-tert-butylpicene.
- Conversion to a series of picenophanes (6-10).
- X-ray crystallography for structural analysis of tub-shaped [2,2](5,8)picenophanediene.
- Experimental estimation of tub-to-tub inversion barrier.
- Ultrafast time-resolved emission spectroscopy.
Main Results:
- Successful synthesis of novel picenophanes with varying bridge structures.
- X-ray structure revealed a tub-shaped conformation for the cis-ethylene linked picenophane.
- An inversion barrier of 18.7 kcal/mol was determined for an isopropyl-substituted derivative.
- Distinct photophysical behaviors were observed, including weak exciton delocalization and dual emission (exciton and excimer).
- Excimer formation mechanism elucidated as a two-state reversible reaction with fast structural deformation (20 ps lifetime).
Conclusions:
- Slight structural modifications in picenophane bridges significantly alter photophysical properties.
- Picenophanes demonstrate potential for harnessing inter-moiety reactions.
- The study provides insights into the relationship between molecular structure, dynamics, and photophysics in complex π-systems.
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01:26Thermal and Photochemical Electrocyclic Reactions: Overview
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01:28Stability of Conjugated Dienes
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Selection Rules: Photochemical Activation
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