Amino-Substituted 1,3-Diazaazulenes: Synthesis, Structural Studies, Reactivity, and Photophysical Properties
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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en
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13
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Chemistry: A European Journal, Volume 31, issue 27
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 2nd 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 (λem_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.Description
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Leino, T O, Bannykh, A, Eskelinen, T, Belyaev, A & Pihko, P M 2025, 'Amino-Substituted 1,3-Diazaazulenes: Synthesis, Structural Studies, Reactivity, and Photophysical Properties', Chemistry: A European Journal, vol. 31, no. 27, e202500861. https://doi.org/10.1002/chem.202500861