文献类型：期刊文献

英文题名：Higher Order π-Conjugated Polycyclic Hydrocarbons with Open-Shell Singlet Ground State: Nonazethrene versus Nonacene

作者：Huang, Rui[1,2];Phan, Hoa[1];Herng, Tun Seng[3];Hu, Pan[1];Zeng, Wangdong[1];Dong, Shao-qiang[1];Das, Soumyajit[1];Shen, Yongjia[2];Ding, Jun[3];Casanova, David[4,5,6];Wu, Jishan[1,7]

机构：[1]Natl Univ Singapore, Dept Chem, Sci Dr 3, Singapore 117543, Singapore;[2]East China Univ Sci & Technol, Dept Chem, Key Lab Adv Mat, 130 Meilong Rd, Shanghai 200237, Peoples R China;[3]Natl Univ Singapore, Dept Mat Sci & Engn, Singapore 119260, Singapore;[4]Euskal Herriko Unibertsitatea, IKERBASQUE Basque Fdn Sci, Paseo Manuel de Lardizabal 4, Dgonostia San Sebastian 20018, Euskadi, Spain;[5]Euskal Herriko Unibertsitatea, Donostia Int Phys Ctr, Paseo Manuel de Lardizabal 4, Dgonostia San Sebastian 20018, Euskadi, Spain;[6]Euskal Herriko Unibertsitatea, Kimika Fak, Paseo Manuel de Lardizabal 4, Dgonostia San Sebastian 20018, Euskadi, Spain;[7]ASTAR, Inst Mat Res & Engn, 2 Fusionopolis Way,Innovis 08-03, Singapore 138634, Singapore

年份：2016

卷号：138

期号：32

起止页码：10323

外文期刊名：JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

收录：;EI(收录号：20163502748217);WOS:【SCI-EXPANDED(收录号:WOS:000381715700043)】；

基金：This work was financially supported by the MOE Tier 3 Programme (MOE2014-T3-1-004), Tier 2 grant (MOE2014-T2-1-080), and A*STAR JCO grant (1431AFG100). R.H. acknowledges the scholarship support from the Chinese Scholarship Council ([2014]3026). D.C. acknowledges the Basque Government (project IT588-13) for financial support and SGIker for allocation of computational resources.

语种：英文

外文关键词：Nuclear magnetic resonance - Shellfish - Ground state - Molecular orbitals - Molluscs - Energy gap - Sodium compounds - Calculations - Shells (structures)

摘要：Higher order acenes (i.e., acenes longer than pentacene) and extended zethrenes (i.e., zethrenes longer than zethrene) are theoretically predicted to have an open-shell singlet ground state, and the radical character is supposed to increase with extension of molecular size. The increasing radical character makes the synthesis of long zethrenes and acenes very challenging, and so far, the longest reported zethrene and acene derivatives are octazethrene and nonacene, respectively. In addition, there is a lack of fundamental understanding of the differences between these two closely related open-shell singlet systems. In this work, we report the synthesis a challenging nonazethrene derivative, HR-NZ, and its full structural and physical characterizations including variable temperature NMR, ESR, SQUID, UV-vis-NIR absorption and electrochemical measurements. Compound HR-NZ has an open-shell singlet ground state with a moderate diradical character (y(0) = 0.48 based on UCAM-B3LYP calculation) and a small singlet triplet gap (Delta ES-T = 5.2 kcal/mol based on SQUID data), thus showing Magnetic activity at room temperature. It also shows amphoteric redox behavior, with a small electrochemical energy gap (1.33 eV). Its electronic structure and physical properties are compared with those of Anthony's nonacene derivative JA-NA and other zethrene derivatives. A more general comparison between higher order acenes and extended zethrenes was also conducted on the basis of ab initio electronic structure calculations, and it was found that zethrenes and acenes have very different spatial localization of the unpaired electrons. As a result, a faster decrease of singlet triplet energy sap and a. faster increase of radical character with increase of the number of. benzenoid rings were observed in zethrene series. Our Studies,reveal that spatial localization of the frontier molecular orbitals play, a very important role on the nature of radical character as:well as the excitation energy.