Amino‐Substituted 1,3‐Diazaazulenes: Synthesis, Structural Studies, Reactivity, and Photophysical Properties
Year: 2025
Type: article
Abstract: We report a facile method for the functionalization of the 1,3‐diazaazulene core at the C4, C6, and C8 positions via regioselective bromination and subsequent substitution with amine nucleophiles. Both steps can be controlled to enable selective mono‐, di‐, or trisubstitution at C4, C6, or C8. Crystallographic studies revealed significant distortion from planarity in the aromatic core of the highly substituted 2,4,6,8‐tetra‐amino‐1,3‐diazaazulenes, further confirmed by density functional theory (DFT). The tetra‐aminosubstituted diazaazulenes displayed unusual hydrolytic reactivity in acidic media, a reaction that is rare with aminobenzenes and appears to be promoted in this case by structural distortion. The combinatorial functionalization of 1,3‐diazaazulene resulted in soft‐tunable optical properties observed in both solution and poly(methyl methacrylate) (PMMA) films. Strong low‐energy absorptions ( ε = 11,800–38,500 M −1 ·cm −1 ), arise from π–π* transitions, as supported by our 2 nd order approximate coupled‐cluster (CC2) calculations. Consequently, the fluorescence relaxation mechanism involves a π*–π transition mixed with charge transfer, producing emission spanning from deep blue to yellow ( λ em_max = 428–535). We anticipate that the modular synthesis, tunable substitution patterns, and consequent modulation of both reactivity and photophysical properties renders the 1,3‐diazaazulene core an intriguing molecular platform for a variety of applications.
Source: Chemistry - A European Journal
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,640
Funder: Academy of Finland
OpenAlex ID: W4408889911