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Oligotriarylamines with a Pyrene Core: A Multicenter Strategy for Enhancing Radical Cation and Dication Stability and Tuning Spin Distribution
Author(s) -
Nie HaiJing,
Yao ChangJiang,
Shao JiangYang,
Yao Jiannian,
Zhong YuWu
Publication year - 2014
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.201403847
Subject(s) - dication , chemistry , radical ion , pyrene , photochemistry , density functional theory , electron paramagnetic resonance , amine gas treating , singlet state , hyperfine structure , crystallography , molecule , computational chemistry , ion , excited state , organic chemistry , nuclear magnetic resonance , physics , quantum mechanics , nuclear physics
Monoamine 1 , diamines 2 – 4 , triamine 5 , and tetraamine 6 have been synthesized by substituting dianisylamino groups at the 1‐, 3‐, 6‐, and/or 8‐positions of pyrene. Diamines 2 – 4 differ in the positions of the amine substituents. No pyrene–pyrene interactions are evident in the single‐crystal packing of 3 , 4 , and 6 . With increasing numbers of amine substituents, the first oxidation potential decreases progressively from the mono‐ to the tetraamine. These compounds show intense charge‐transfer (CT) emission in CH 2 Cl 2 at around 530 nm with quantum yields of 48–68 %. Upon stepwise oxidation by electrolysis or chemical oxidation, these compounds were transformed into radical cations 1 ⋅+ – 6 ⋅+ and dications 2 2+ – 6 2+ , which feature strong visible and near‐infrared absorptions. Time‐dependent density functional theory studies suggested the presence of localized transitions from the pyrene radical cation and aminium radical cation, intervalence CT, and CT between the pyrene and amine moieties. Spectroscopic studies indicated that these radical cations and dications have good stability. Triamine 5 and tetraamine 6 formed efficient CT complexes with tetracyanoquinodimethane in solution. The results of EPR spectroscopy and density functional theory calculations suggested that the dications 2 2+ – 4 2+ have a triplet ground state, whereas 5 2+ and 6 2+ have a singlet ground state. The dication of 1,3‐disubstituted diamine 4 exhibits a strong EPR signal.