Crystal structure of 1,2-bis[2-n-hexyl-5-(2,2-dicyanovinyl)-3-thienyl)]- 3,3,4,4,5,5-hexafluorocyclopent-1-ene, C33H30F6N4S2

Abstract

Source of materialThe title compound was synthesized in 35 % total yield by a literature method [1,2] using 5-n-hexyl-thiophene-2-carbaldehyde as the starting material. Crystals suitable for X-ray analysis were grown from solution (diethyl ether/hexane 1:2) by slow evaporation at room temperature (m.p. 390.9 -391.2 K). Elemental analysis -found: C, 60.19 %; H, 4.44 %; N, 8.12 %; calculated for C33H30F6N4S2: C, 59.99 %; H, 4.58 %; N, 8.48 %. 'Η NMR, 13 C NMR and IR data are available in the CIF. Experimental detailsAll Η atoms attached to C were fixed geometrically and treated as riding with d(C-H) = 0.96 Â (methyl) or 0.93 Â (aromatic) with t/iso(H) = 1.2 i/eq(aromatic) or ίΛ*>(Η) = 1.5 í/eq(methyl). Bonds between theatomsCl toC5,CrtoC5',C17andF3 were subject to a 'rigid bond' restraint, i.e. the components of the anisotropic displacement parameters in the direction of the bond were restrained to be equal within an effective standard deviation set to 0.01. The same atoms were also restrained with an effective standard deviation of 0.01 to have the same i/y components. The distance cutoff for this restraint was set to 1.70 Â. Using different "effective standard deviation" for the terminational atoms C1 and CI', the default setting (0.08) of command was used for the terminational atoms. DiscussionOrganic photochromic diarylethenes have attracted much attention for their potential application in optical memory media and optical switches [3,4], In our previous crystallographic studies of photochromic diarylethenes, we reported. l,2-bis[2-«-pentyl-5-(2,2-dicyanovinyl)-3-thienyl)]-3,3,4,4,5,5-hexafluorocyclopent-l-ene [1,3] and l,2-bis[2-«-butyl-5-(2,2-dicyanovinyl)-3-thienyl)]-3,3,4,4,5,5-hexafluorocyclopent-l-ene [4,6]. These studies are extended to the n-hexyl analog, in order to investigate the substituent effect at the 2-postion of the thiophene on the photochemical properties. The title compound is a new twofold symmetrical hybrid photochromic diarylethene derivative. In the crystal structure, the F atoms of the central hexafluorocyclopentene ring are disordered, with site occupancies of 0.683(6) and 0.317; and the ratio of the disorder of the alky chain is 0.591(6) to 0.409. The molecule adopts a photo-active antiparallel conformation. The distance between the two photo-reactive C atoms is 3.941(3) Â. The dihedral angle between the central cyclopentene ring and the adjacent thiophene ring is 63.4(5)°. The two thiophene rings are condensed via the C15=C15A double bond (symmetry operator A: -x+2,y,-z+i/2) (figure, top) while the other bonds in the ring are clearly single bonds. The two n-hexyl groups are located on different sides of the double bond. This configuration is crucial to allow the compound to exhibit photochromic and photoinduced properties [7]. It may allows breaking of the central hexafluoro-cyclopentene C=C double bond to form a new C-C single bond to be symmetry allowed and the molecule thus may undergo a phototransition and exhibit photochromic and photoinduced properties. The dihedral angles bet...