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- 저자 : Webster Richard D. (검색결과 3 건)
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Halilovic, Dzeneta,Budanović,, Maja,Wong, Zeng R.,Webster, Richard D.,Huh, June,Stuparu, Mihaiela C. American Chemical Society 2018 Journal of organic chemistry Vol.83 No.7
<P>The first family of extended and fluorinated corannulenes is prepared through a highly efficient and modular synthetic strategy. In this strategy, corannulene aldehyde could be combined with the fluorine-carrying phosphonium ylides to furnish stilbene-like vinylene precursors. A photochemically induced oxidative cyclization process of these precursors gives rise to the fluorinated and curved polycyclic aromatic hydrocarbons. A UV-vis absorption study shows that aromatic extension results in a bathochromic shift of about 12 nm. Fluorination further shifts the absorption spectrum to the red region, and a maximum shift of about 22 nm is detected for a compound carrying two trifluoromethyl groups. A cyclic and square-wave voltammetry investigation reveals that the extension of the corannulene scaffold increases the reduction potential by 0.11 V. Placement of fluorine or trifluoromethyl groups further enhances the electron affinities. In this regard, the presence of one trifluoromethyl group equals the effect of three aromatic fluorine atoms. Molecules with two trifluoromethyl groups, meanwhile, exhibit the highest reduction potentials of −1.93 and −1.83 V. These values are 0.37 and 0.46 V higher than those of the parental corannulene and demonstrate the utility of the present design concept by efficiently accessing effective electron acceptors based on the buckybowl motif.</P> [FIG OMISSION]</BR>
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Zeng, Zebing,Ishida, Masatoshi,Zafra, José,L.,Zhu, Xiaojian,Sung, Young Mo,Bao, Nina,Webster, Richard D.,Lee, Byung Sun,Li, Run-Wei,Zeng, Wangdong,Li, Yuan,Chi, Chunyan,Navarrete, Juan T. Lo American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.16
<P><I>p</I>-Quinodimethane (<I>p</I>-QDM) is a fundamental building block for the design of π-conjugated systems with low band gap and open-shell biradical character. However, synthesis of extended <I>p</I>-QDMs has usually suffered from their intrinsic high reactivity and poor solubility. In this work, benzannulation together with terminal cyano-substitution was demonstrated to be an efficient approach for the synthesis of a series of soluble and stable tetracyano-oligo(<I>N</I>-annulated perylene)quinodimethanes <B><I>n</I>Per-CN</B> (<I>n</I> = 1–6), with the longest molecule having 12 <I>para</I>-linked benzenoid rings! The geometry and electronic structures of these oligomers were investigated by steady-state and transient absorption spectroscopy, nuclear magnetic resonance, electron spin resonance, superconducting quantum interference device, and FT Raman spectroscopy assisted by density functional theory calculations. They showed tunable ground states, varying from a closed-shell quinoidal structure for monomer, to a singlet biradical for dimer, trimer, and tetramer, and to a triplet biradical for pentamer and hexamer. Large two-photon absorption cross-section values were observed in the near-infrared range, which also exhibited a clear chain-length dependence.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-16/ja402467y/production/images/medium/ja-2013-02467y_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja402467y'>ACS Electronic Supporting Info</A></P>
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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 D.,Ló,pez Navarrete, Juan T.,Kim, Dongh American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.36
<P>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 (<B>HZ-TIPS</B>) and octazethrene (<B>OZ-TIPS</B>) 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 <B>HZ-TIPS</B> has a closed-shell ground state while its octazethrene analogue <B>OZ-TIPS</B> with a smaller energy gap exists as an open-shell singlet biradical with a large measured biradical character (<I>y</I> = 0.56). Large two-photon absorption (TPA) cross sections (σ<SUP>(2)</SUP>) were determined for <B>HZ-TIPS</B> (σ<SUP>(2)</SUP><SUB>max</SUB> = 920 GM at 1250 nm) and <B>OZ-TIPS</B> (σ<SUP>(2)</SUP><SUB>max</SUB> = 1200 GM at 1250 nm). In addition, <B>HZ-TIPS</B> and <B>OZ-TIPS</B> show a closely stacked 1D polymer chain in single crystals.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-36/ja304618v/production/images/medium/ja-2012-04618v_0015.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja304618v'>ACS Electronic Supporting Info</A></P>
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