We report a novel method for the formation of fully extended, oriented chains of polyacetylene (CH)x constrained within the channels of a urea inclusion complex (UIC) based on the photo-elimination of iodine from the guest 1,4-diiodo-1,3-butadiene (DIBD). The reported crystal structure of DIBD:UIC has the iodine atoms in contact in a hexagonal channel.[1] We used Raman spectroscopy measurements to probe the resulting conjugated polyene chains. Ultraviolet or visible irradiation of the DIBD:UIC results in the appearance of new resonance-enhanced Raman modes around 1125 and 1509 cm-1 as illustrated in Figure 1.The Raman spectra of the resulting confined polyene chains are nearly identical to spectra of trans-(CH)x prepared by solution methods. This all-trans geometry is anticipated since the included guests inside conventional urea channels are generally in the fully extended all-trans conformation. The intermediates in this process, I-(CH=CH-CH=CH)n-I, n= 2, 3, 4 were prepared from DIBD by reductive iodine elimination. The structural, spectral, and photochemical properties of urea inclusion complexes of 1,8-diiodo-1,3,5,7-octatetraene will also be discussed. Figure 1: Raman scattering spectra of DIBD/UICs (a) before and (b) after 6 min of 532 nm irradiation. The arrows mark the positions of the new Raman product bands at 1125 and 1509 cm-1.[1] Lashua, A. F.; Smith, T. M.; Hu, H.; Wei, L.; Allis, D. G.; Sponsler, M. B.; Hudson, B. S. Cryst. Growth Des. 2013  , 13, 3852-3855.

Oriented, insulated polyacetylene chains in an inclusion complex by photopolymerization

248th National Meeting (2014)

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