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Title: Kinetically blocked stable heptazethrene and octazethrene : closed-shell or open-shell in the ground state?
Authors: Li, Yuan
Heng, Wee-Kuan
Lee, Byung Sun
Aratani, Naoki
Zafra, José L.
Bao, Nina
Lee, Richmond
Sung, Young Mo
Sun, Zhe
Huang, Kuo-Wei
Webster, Richard David
López Navarrete, Juan T.
Kim, Dongho
Osuka, Atsuhiro
Casado, Juan
Ding, Jun
Wu, Jishan
Issue Date: 2012
Source: Li, Y., Heng, W.-K., Lee, B. S., Aratani, N., Zafra, J. L., Bao, N., et al. (2012). Kinetically Blocked Stable Heptazethrene and Octazethrene: Closed-Shell or Open-Shell in the Ground State? Journal of the American Chemical Society, 134(36), 14913-14922.
Series/Report no.: Journal of the American chemical society
Abstract: Polycyclic aromatic hydrocarbons with an open-shell singlet biradical ground state are of fundamental interest and have potential applications in materials science. However, the inherent high reactivity makes their synthesis and characterization very challenging. In this work, a convenient synthetic route was developed to synthesize two kinetically blocked heptazethrene (HZ-TIPS) and octazethrene (OZ-TIPS) compounds with good stability. Their ground-state electronic structures were systematically investigated by a combination of different experimental methods, including steady-state and transient absorption spectroscopy, variable temperature NMR, electron spin resonance (ESR), superconducting quantum interfering device (SQUID), FT Raman, and X-ray crystallographic analysis, assisted by unrestricted symmetry-broken density functional theory (DFT) calculations. All these demonstrated that the heptazethrene derivative HZ-TIPS has a closed-shell ground state while its octazethrene analogue OZ-TIPS with a smaller energy gap exists as an open-shell singlet biradical with a large measured biradical character (y = 0.56). Large two-photon absorption (TPA) cross sections (σ(2)) were determined for HZ-TIPS (σ(2)max = 920 GM at 1250 nm) and OZ-TIPS (σ(2)max = 1200 GM at 1250 nm). In addition, HZ-TIPS and OZ-TIPS show a closely stacked 1D polymer chain in single crystals.
DOI: 10.1021/ja304618v
Rights: © 2012 American Chemical Society.
Fulltext Permission: none
Fulltext Availability: No Fulltext
Appears in Collections:SPMS Journal Articles

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