Stable Tetrabenzo-Chichibabin’s Hydrocarbons: Tunable Ground State and Unusual Transition between Their Closed-Shell and Open-Shell Resonance Forms
- 14 August 2012
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 134 (35), 14513-14525
- https://doi.org/10.1021/ja3050579
Abstract
Stable open-shell polycyclic aromatic hydrocarbons (PAHs) are of fundamental interest due to their unique electronic, optical, and magnetic properties and promising applications in materials sciences. Chichibabin’s hydrocarbon as a classical open-shell PAH has been investigated for a long time. However, most of the studies are complicated by their inherent high reactivity. In this work, two new stable benzannulated Chichibabin’s hydrocarbons 1-CS and 2-OS were prepared, and their electronic structure and geometry in the ground state were studied by various experiments (steady-state and transient absorption spectra, NMR, electron spin resonance (ESR), superconducting quantum interference device (SQUID), FT Raman, X-ray crystallographic etc.) and density function theory (DFT) calculations. 1-CS and 2-OS exhibited tunable ground states, with a closed-shell quinoidal structure for 1-CS and an open-shell biradical form for 2-OS. Their corresponding excited-state forms 1-OS and 2-CS were also chemically approached and showed different decay processes. The biradical 1-OS displayed an unusually slow decay to the ground state (1-CS) due to a large energy barrier (95 ± 2.5 kJ/mol) arising from severe steric hindrance during the transition from an orthogonal biradical form to a butterfly-like quinoidal form. The quick transition from the quinoidal 2-CS (excited state) to the orthogonal biradicaloid 2-OS (ground state) happened during the attempted synthesis of 2-CS. Compounds 1-CS and 2-OS can be oxidized into stable dications by FeCl3 and/or concentrated H2SO4. The open-shell 2-OS also exhibited a large two-photon absorption (TPA) cross section (760 GM at 1200 nm).Keywords
This publication has 92 references indexed in Scilit:
- Organic tailored batteries materials using stable open-shell molecules with degenerate frontier orbitalsNature Materials, 2011
- A Stable Non-Kekulé Singlet Biradicaloid from meso-Free 5,10,20,25-Tetrakis(Pentafluorophenyl)-Substituted [26]Hexaphyrin(1.1.1.1.1.1)Journal of the American Chemical Society, 2010
- Dications of Tetrabenzofulvalenes. Paratropicity and .sigma. Donation in Perpendicular Antiaromatic SystemsJournal of the American Chemical Society, 1994
- Photochemical synthesis of matrix-isolated pleiadeneJournal of the American Chemical Society, 1970
- New Data on BiradicalsRussian Chemical Reviews, 1968
- Syntheses with Triarylvinylmagnesium Bromides. α,γ-Bisdiphenylene-β-phenylallyl, a Stable Free RadicalJournal of the American Chemical Society, 1957
- Carbonium Ions. I. An Acidity Function (C0) Derived from Arylcarbonium Ion Equilibria1Journal of the American Chemical Society, 1955
- The Electron Affinity of Free Radicals. V. Aromatic Derivatives of Dixanthyl and p,p'-Biphenylene-bi-(diphenylmethyl)Journal of the American Chemical Society, 1935
- Über einige phenylierte Derivate des p, p‐DitolylsEuropean Journal of Inorganic Chemistry, 1907
- Ueber einen chinoïden KohlenwasserstoffEuropean Journal of Inorganic Chemistry, 1904