Acta Crystallographica Section C

Crystal Structure Communications

Volume 63, Part 11 (November 2007)

organic compounds

jz3086 scheme

Acta Cryst. (2007). C63, o633-o637 [ doi:10.1107/S0108270107046033 ]

Geometry and bond-length alternation in nonlinear optical materials. I. Standard parameters in two precursors

G. J. Gainsford, M. D. H. Bhuiyan and A. J. Kay

Abstract: 2-{3-Cyano-4-[4-(N-formylanilino)-trans-1,3-butadienyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}propanedinitrile, C₂₂H₁₈N₄O₂, (I), and 2-{3-cyano-4-[6-(N-formylanilino)-trans,trans-1,3,5-hexatrienyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}propanedinitrile, C₂₄H₂₀N₄O₂, (II), show the alternating single/double-bond behaviour of push-pull chromophores. In the two structures, the planar polyene chains are twisted with respect to the furanylidene ring by 18.2 (2) and 12.4 (2)°, respectively. Comparison with structures of related and parent molecules shows subtle but consistent bond-length variations consistent with charge-delocalized structures. Crystal cohesion is provided by various sets of hydrogen bonds, viz. C-H_methylN_cyano and bifurcated (C=C-H)₂O=C in (I), and C-H_{methyl/phenyl}O and C=C-HN_cyano in (II).

Formula: C₂₂H₁₈N₄O₂ and C₂₄H₂₀N₄O₂


	Structure factor file (CIF format) (274.2 kbytes) [ doi:10.1107/S0108270107046033/jz3086Isup2.hkl ] Contains datablock I

	Structure factor file (CIF format) (317.9 kbytes) [ doi:10.1107/S0108270107046033/jz3086IIsup3.hkl ] Contains datablock II

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