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Updated: Jul 16, 2026

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes
Published on: April 1, 2013
Isomeric Dibenzodiindenophenanthrene Diradicaloids: Synthesis, Structures, Properties, and Efficient NIR Photothermal
Qing Jiang1, Xinyi Zheng1, Jianchao Li2
1College of Chemistry and Bioengineering, Hunan University of Science and Engineering, Yongzhou, China.
Abstract:
Structural isomerism is a powerful strategy to modulate the fundamental properties of organic diradicaloids. Herein, we report the synthesis and characterization of a series of isomeric open-shell polycyclic hydrocarbons (PHs) (1-3) based on the dicyclopenta[b,j]phenanthrene framework, whose diradical properties are compared with those of their anthracene-based isomers. Combined experimental and theoretical studies reveal that subtle structural isomerism dictates their distinct electronic structures and properties, featuring large diradical characters (y0 = 0.54-0.72), small singlet-triplet energy gaps (ΔES-T = -0.99 to -2.79 kcal/mol), and narrow HOMO-LUMO energy gaps (0.90-1.16 eV). They exhibit remarkable multistage reversible redox behaviors, forming stable radical cations, radical anions, dications, and dianions, with the dicationic structures unambiguously confirmed by x-ray crystallographic analysis. Notably, compounds 1-3 display fast responses to near-infrared (NIR) laser irradiation, along with excellent photothermal (PT) stability, good PT conversion efficiency and high-quality PT imaging performance. This work not only provides deep insights into the structure-property relationships of isomerism-engineered diradical PHs but also establishes a robust molecular platform for advanced NIR PT materials.
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Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...
Structure of Conjugated Dienes
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...