期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 135, 期 21, 页码 8031-8040出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja402371f
关键词
-
资金
- MEXT, Japan [22350021, 23750045]
- Noguchi Institute
- Asahi Glass Foundation
- Grants-in-Aid for Scientific Research [24655036, 22350021, 23750045, 25810023, 25109536] Funding Source: KAKEN
A novel pyrrole-fused azacoronene family was synthesized via oxidative cyclodehydrogenation of the corresponding hexaarylbenzenes as the key step, and the crystal structures of tetraazacoronene 3b and triazacoronene 4a were elucidated. The photophysical properties for neutral compounds 1-4 were investigated using steady-state UV-vis absorption/emission spectroscopy and time resolved spectroscopy (emission spectra and lifetime measurements) at both room temperature and 77 K. The observation of both fluorescence and phosphorescence allowed us to estimate the small S-1-T-1 energy gap (Delta ES-T) to be 0.35 eV (la), 0.26 eV (2a), and 0.36 eV (4a). Similar to the case of previously reported hexapyrrolohexaazacoronene 1 (HPHAC), electrochemical oxidation revealed up to four reversible oxidation processes for all of the new compounds. The charge and spin delocalization properties of the series of azacoronene pi-systems were examined using UV-vis-NIR absorption, ESR, and NMR spectroscopies for the chemically generated radical cations and dications. Combined with the theoretical calculations, the experimental results clearly demonstrated that the replacement of pyrrole rings with dialkoxybenzene plays a critical role in the electronic communication, where resonance structures significantly contribute to the thermodynamic stability of the cationic charges/spins and determine the spin multiplicities For HPHAC 1 and pentaazacoronene 2, the overall aromaticity predicted for dosed shell dications 1(2+) and 2(2+) was primarily based on the theoretical calculations, and the open shell singlet biradical or triplet character was anticipated for tetraazacoronene 3(2+) and triazacoronene 4(2+) with the aid of theoretical calculations These polycyclic aromatic hydrocarbons (PAHs) represent the first series of nitrogen containing PAHs that can be multiply oxidized.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据