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A Spherically Shielded Triphenylamine and Its Persistent Radical Cation
Author(s) -
Schaub Tobias A.,
Mekelburg Theresa,
Dral Pavlo O.,
Miehlich Matthias,
Hampel Frank,
Meyer Karsten,
Kivala Milan
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202000355
Subject(s) - shielded cable , triphenylamine , photochemistry , computer science , chemistry , telecommunications
This work reports the design and synthesis of a sterically protected triphenylamine scaffold which undergoes one‐electron oxidation to form an amine‐centered radical cation of remarkable stability. Several structural adjustments were made to tame the inherent reactivity of the radical cation. First, the parent propeller‐shaped triphenylamine was planarized with sterically demanding bridging units and, second, protecting groups were deployed to block the reactive positions. The efficiently shielded triphenylamine core can be reversibly oxidized at moderate potentials (+0.38 V, vs. Fc/Fc + in CH 2 Cl 2 ). Spectroelectrochemistry and chemical oxidation studies were employed to monitor the evolution of characteristic photophysical features. To obtain a better understanding of the impact of one‐electron oxidation on structural and electronic properties, joint experimental and computational studies were conducted, including X‐ray structural analysis, electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations. The sterically shielded radical cation combines various desirable attributes: A characteristic and unobstructed absorption in the visible region, high stability which enables storage for weeks without spectroscopically traceable degradation, and a reliable oxidation/re‐reduction process due to effective screening of the planarized triphenylamine core from its environment.