Pure Appl. Chem., 2008, Vol. 80, No. 3, pp. 475-484
doi:10.1351/pac200880030475
Heterophenes revisited*
Tien-Yau Luh, Hsin-Chieh Lin, and Chih-Ming Chou
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
Abstract:
By employing the furan annulation protocol, a new series of furan-containing teraryl [n.2]cyclophenes (n = 2-6 and 12) are prepared. These cyclophenes exhibit charge-transfer character in the absorption spectra and unusually large Stokes shifts in the emission spectra. They have neither particularly strong electron-donating moieties nor electron-withdrawing groups, but exhibit unusual second-order nonlinear optical (NLO) properties. The π-systems in teraryl system and in the bridging double bond are highly twisted. Interaction between these twisted π-systems may account for the significant enhancement in hyperpolarizability. Thiophene analog behaved similarly. The five-membered heteroaromatic rings may not only serve as electron donors, but also may accommodate the appropriate geometry to enable the interactions between the oligoaryl systems and the double bond leading to unusual photophysical and NLO properties.
Keywords: bridging double bond; cyclophenes; furan-containing oligoaryls; nonlinear optical properties; twisted π-system.
*Paper based on a presentation at the 12th International Symposium on Novel Aromatic Compounds (ISNA-12), 22-27 July 2007, Awaji Island, Japan. Other presentations are published in this issue, pp. 411-667.
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