Stable Phenanthrene-Fused 1,2,4-Triazinyl Radicals with Ultra-narrow Electrochemical Gap Enabled by Attenuated Fusion-Ring Aromaticity
Year: 2026
Type: preprint
Abstract: The design of organic materials with narrow electrochemical gaps (Egap) is critical for modern electronics, yet achieving such narrow gaps while retaining robust stability and facile processability remains a fundamental challenge. Herein, we report a new strategy based on targeted attenuation of aromaticity in π-extended Blatter-type radicals that enables notable gap reduction to 0.75 eV—the lowest reported for this class. We prepare the robust Blatter radical derivatives 1 and 1-tBu, in which its triazinyl moiety is fused with the central ring of phenanthrene, creating an annulated ring system with reduced aromaticity, compared to classical Blatter radicals. Our studies indicate that reducing fusion-ring aromaticity lowers substantially the gas-phase ionization potential while moderating neutral-state solvation enhancement that typically accompanies π-extension, thereby preserving larger differential solvation stabilization and consequently a substantial Egap reduction. Experimental Egap is observed to exhibit high correlation with the DFT-computed total spin density on the triazinyl-fused ring for the studied Blatter derivatives. In addition, sublimable 1 forms well-ordered thin films of intact radicals on Au(111) surface, highlighting its practical processability. This work establishes aromaticity modulation as an effective strategy for stable, narrow-gap materials, based upon neutral radicals.
Source: ChemRxiv
Institutions: Beijing Normal University, Chinese Academy of Sciences
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7154617086